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Using Attributional Life Cycle Assessment to Estimate Climate-Change Mitigation Benefits Misleads Policy Makers
Abstract
Life cycle assessment (LCA) is generally described as a tool for environmental decision making. Results from attributional LCA (ALCA), the most commonly used LCA method, often are presented in a way that suggests that policy decisions based on these results will yield the quantitative benefits estimated by ALCA. For example, ALCAs of biofuels are routinely used to suggest that the implementation of one alternative (say, a biofuel) will cause an X% change in greenhouse gas emissions, compared with a baseline (typically gasoline). However, because of several simplifications inherent in ALCA, the method, in fact, is not predictive of real-world impacts on climate change, and hence the usual quantitative interpretation of ALCA results is not valid. A conceptually superior approach, consequential LCA (CLCA), avoids many of the limitations of ALCA, but because it is meant to model actual changes in the real world, CLCA results are scenario dependent and uncertain. These limitations mean that even the best practical CLCAs cannot produce definitive quantitative estimates of actual environmental outcomes. Both forms of LCA, however, can yield valuable insights about potential environmental effects, and CLCA can support robust decision making. By openly recognizing the limitations and understanding the appropriate uses of LCA as discussed here, practitioners and researchers can help policy makers implement policies that are less likely to have perverse effects and more likely to lead to effective environmental policies, including climate mitigation strategies.
... Other policies are addressed by Steurer (2010), Plevin, Delucchi, and Creutzig (2014), and Markard, Raven, and Truffer (2012). Steurer (2010) analyses the role of governments in promoting corporate social responsibility (CSR) to characterize public policies related to CSR in Europe, including regulatory approaches, incentives, voluntary initiatives, and partnerships with businesses and other stakeholders. ...
... Steurer (2010) analyses the role of governments in promoting corporate social responsibility (CSR) to characterize public policies related to CSR in Europe, including regulatory approaches, incentives, voluntary initiatives, and partnerships with businesses and other stakeholders. Plevin, Delucchi, and Creutzig (2014) evaluate the use of Attributional Life Cycle Assessment (ALCA) as a tool for estimating climate-change mitigation benefits and their implications. Given that ALCA is not predictive of real-world impacts on climate change, a conceptually superior approach, namely consequential LCA (CLCA), avoids many of its limitations. ...
... ,Meckling, Sterner, and Wagner (2017),Steurer (2010),Plevin, Delucchi, and Creutzig (2014),Markard, Raven, and Truffen (2012),Rodrik (2014), Kern, Rogge, and Howlett(2019), and Lamperti et al. (2019)*. The general framework: development and sustainability Stern (2008)*, Acemoglu et al. (2012)*, Farberger (2018), Kemp and Never (2017), Mealy and Teytelboym (2022), Stern and Stiglitz (2023)*, and Wieczorek (2018) ...
... There is a long record of vivid discussions about ALCA and CLCA, one part of the community applying only the most common ALCA, another one considering that CLCA is the best way to represent environmental responsibility (Plevin et al. 2014;Weidema et al. 2018), while the vast majority has mixed appreciations or recognizes that each approach has different adequacies for different purposes (Curran et al. 2005;Ekvall et al. 2016;Brander et al. 2019). To our understanding, the different practices can be seen as a continuum between pure attributional and pure consequential approaches, as many approaches are mixed, for instance, consequential models used with attributional background datasets (Weidema 2017). ...
... But this continuum of potential quantification rules is a major and transversal challenge that leaks onto all the steps to address carbon neutrality plans. This question must be addressed in the nexus of carbon neutrality pathways when it comes to set system boundaries (Zamagni et al. 2012;Plevin et al. 2014;Weidema et al. 2018 (Plevin et al. 2014) and neutralizing actions, as well as indirect effects of investments (Sandén and Karlström 2007). In particular, assessing the impact of global or very large-scale system transitions needed to reach carbon neutrality might be highly unreliable without a consequential approach, as this latter considers physical and economic constraints (Weidema et al. 2018) while ALCA does not. ...
... But this continuum of potential quantification rules is a major and transversal challenge that leaks onto all the steps to address carbon neutrality plans. This question must be addressed in the nexus of carbon neutrality pathways when it comes to set system boundaries (Zamagni et al. 2012;Plevin et al. 2014;Weidema et al. 2018 (Plevin et al. 2014) and neutralizing actions, as well as indirect effects of investments (Sandén and Karlström 2007). In particular, assessing the impact of global or very large-scale system transitions needed to reach carbon neutrality might be highly unreliable without a consequential approach, as this latter considers physical and economic constraints (Weidema et al. 2018) while ALCA does not. ...
Purpose : Planning a transition towards sustainable carbon neutrality at the organization level raises several accounting challenges. This paper aims to shed light on key challenges, highlight answers from current accounting standards and guidance, point out potential inconsistencies or limits, and outline potential solutions from the industrial ecology community through systemic environmental assessment tools, such as life cycle assessment (LCA) and environmentally-extended input-output (EEIO) analysis. Results and discussion: We propose a Measure-Reduce-Neutralize-Control sequence allowing organizations to plan their sustainable net-zero strategy, and discuss 24 accounting challenges occurring within this sequence. We then outline ways forward for organizations planning their carbon neutrality trajectory, pointing to existing resources, and for guidelines providers and the industrial ecology communities to address current limitations in the development of future accounting methods and guidelines. Overarching solutions to many accounting issues are to develop comprehensive, open-source, and high-quality life cycle inventory databases, to enable improved dynamic assessments and prospective LCA through integrated assessment models, to refine methods for assessing mineral scarcity and environmental impacts, the supply in some metals being expected to be a bottleneck to the energy transition, and to identify the appropriate climate metrics for planning sustainable carbon neutrality pathways at the organizational level.
... As stated by Plevin et al. (2014) [42], ALCA is not designed to study the effect of changes in production systems. Still, it is typically applied to hot-spot identification and generic consumer information. ...
... As stated by Plevin et al. (2014) [42], ALCA is not designed to study the effect of changes in production systems. Still, it is typically applied to hot-spot identification and generic consumer information. ...
The decarbonization process of the industry and the heating sector, underway in Europe, directly involves heating, cooling, ventilation, and air conditioning systems. In this context, heat pump technologies play a key role in having the ability to be powered by decarbonized energy carriers (i.e., electricity from renewables for vapor compression cycle, hydrogen for absorption cycle, etc.), as well as harnessing renewable or waste heat, in different applications (i.e., industry, district heating networks, and civil sector). The European Commission considers the life cycle assessment method one of the leading methodologies for environmental metrics. Many scientific studies related to analyzing the environmental profile of heat pumps have been written using this method. With the aim to investigate the outcomes achieved and modeling approaches applied, this study reviews existing environmental life cycle assessment studies of (i) high-temperature, (ii) large-size (over 300 kWth), and (iii) medium and small-size heat pumps. In total, 19 articles containing 637 scenarios were found in the literature to be relevant to the research aim. The study analyzes different heat pump technologies (i.e., vapor compression, absorption, and indirect Stirling cycles). The analysis shows that the use phase is the main contributor: (i) average value of 94.6% for the global warming potential, (ii) 69.9% for abiotic depletion potential indicator (metals and minerals). The analysis reveals that life cycle assessment studies apply a rather narrow approach and lack variability in modeling. For future research, it is recommended that the thermodynamic behavior of the heat pumps be properly simulated or monitored. In addition, a stochastic evaluation shall be included in the analysis to reduce and highlight the uncertainty of the results, especially the global sensitivity analysis. Finally, high-temperature heat pumps shall also be investigated using the consequential approach to understand better the environmental consequences of installation in an industrial production process.
... Based on an average wheat yield of 4,000 kg per hectare, the carbon footprint per kilogram of wheat is calculated as (6): 917.5 ÷ 4000 = 0.229 kg CO₂e per kg of wheat (6) This value represents the baseline emissions associated with wheat production and is an essential benchmark for sustainability improvements in the agricultural sector. ...
... Life Cycle Assessment (LCA) is a scientific approach for evaluating the environmental impact of products, processes, or services throughout their life cycle [6]. It follows a cradle-to-grave methodology, considering all stages from raw material extraction, production, distribution, use, and disposal. ...
The agri-food sector is a major contributor to greenhouse gas (GHG) emissions, accounting for approximately 30% of global energy consumption and a substantial share of CO₂, CH₄, and N₂O emissions. As global food systems transition toward sustainability, carbon footprint quantification has become critical for reducing environmental impacts and achieving carbon neutrality goals aligned with the European Green Deal. This paper provides a comprehensive review of methodologies for carbon footprint assessment, including the GHG Protocol – Product Standard, ISO 14064, ISO 14067, Life Cycle Assessment (LCA), and PAS 2050, and their applications in food production systems. A case study on the wheat-to-bread supply chain illustrates the practical application of these frameworks in carbon footprint calculation. The study explores key challenges in carbon footprint tracking, such as data availability and quality issues, complexity of global supply chains, standardization gaps, and financial constraints for small and medium-sized enterprises (SMEs). It further highlights emerging digital technologies, including artificial intelligence (AI), blockchain, and IoT sensors, which enhance emission monitoring, optimize agricultural inputs, and improve transparency in food supply chains. Additionally, the study examines the role of policy frameworks, particularly EU regulations, and the impact of consumer behavior on sustainable food choices. Findings indicate that livestock and fisheries remain the highest-emitting subsectors, while plant-based foods have significantly lower carbon footprints. Integrating digital solutions, standardized methodologies, and regulatory incentives is crucial for improving carbon accounting accuracy and accelerating decarbonization efforts. The paper concludes with recommendations for policymakers, industry stakeholders, and researchers, emphasizing harmonized reporting frameworks, improved access to open carbon databases, and investment in climate-smart agriculture. Strengthening consumer engagement and implementing eco-labeling strategies can further drive demand for low-carbon food products, supporting the transition toward a sustainable and climate-resilient food system.
... This is the case for inventory modelling (Weidema et al. 1999;Ekvall 2020) as well as for characterization Boulay et al. 2020). The distinction is, at least for life cycle inventory analysis (LCI), often connected to that of attributional versus consequential LCA: attributional LCA (ALCA) would use average data, and consequential LCA (CLCA) would use marginal data (Rebitzer et al. 2004;Mathiesen et al. 2009;Finnveden et al. 2009;Frischknecht & Stucki 2010;Zamagni et al. 2012;Plevin et al. 2014;Finnveden & Potting 2014;Ekvall 2020;NAS 2022;Krantz et al. 2023;Bastos et al. 2023), sometimes using a slightly different terminology (Tillman 2000;Werner 2005), and occasionally challenged as well (ILCD 2010;Yang 2016;Provost-Savard & Majeau-Bettez 2024). ...
... In doing so, we first recognize that the terms "average" and "marginal" are not stand-alone words (even though Plevin et al. (2014) use them as such: "whereas ALCA is … average, CLCA ideally is … marginal"), but that they are adjectives that serve to specify a noun. For this, we find several options: "data," "process," "impact," etc. ...
Introduction
In the literature on LCA, one often finds the terms “marginal” and “average,” often in combination with words like “data,” “process,” “emission,” or “characterisation factor.” However, the meaning of these terms appears to differ between sources. This paper aims to clarify the situation.
Critical analysis
We review the various definitions and interpretations of the terms “marginal” and “average” in economics, LCI and LCIA. We also study the role of various related terms, such as “linear” and “incremental.” It turns out that the term “marginal” is used for characterizing processes in some sources and for characterizing the data that describes processes in other sources. These two interpretations are shown to differ substantially in a hypothetical example. We also note that the situation in the LCIA literature differs markedly from that in the LCI literature.
Conclusion and discussion
We propose to distinguish three concepts, marginal, average, and average marginal, and offer verbal definitions, mathematical equations, and a numerical example with a graphical interpretation. We also draw an agenda to research the implications for the attributional-consequential debate, the development of databases and software, and several other topics. This may also help to bring more insights in the continuing controversy on consequential versus attributional LCA.
... Thus, it is crucial that biogas is used as a replacement of fossil energy for the implementation of biogas production to be environmentally beneficial. The actual impacts on the market are highly uncertain due to the complexity of economic systems and human behavior (Ekvall & Weidema 2004;Plevin et al. 2014;York 2012). The increased production of biogas in a region will have effects on the price of energy in the region, which could have an impact on the regional demand, with secondary effects on the global market with high associated uncertainty (Plevin et al. 2014). ...
... The actual impacts on the market are highly uncertain due to the complexity of economic systems and human behavior (Ekvall & Weidema 2004;Plevin et al. 2014;York 2012). The increased production of biogas in a region will have effects on the price of energy in the region, which could have an impact on the regional demand, with secondary effects on the global market with high associated uncertainty (Plevin et al. 2014). As shown in the market modelling study of York (2012), it is not enough to produce more bioenergy to achieve a corresponding decrease in fossil energy use; this needs to come hand in hand with policy instruments. ...
Cover crops offer a potential biogas feedstock, and to enable continuous operation of the biogas plant, ensiling can be used for biomass preservation. The aim of the present study was to assess the environmental impacts of biogas production at an organic dairy farm for two modelled scenarios: (1) harvesting and ensiling of cover crops and cereal straw and co-digestion with cattle manure, or (2) mono-digestion of cattle manure and direct cover crop soil incorporation. The biogas scenarios were modelled in a consequential LCA in relation to a common baseline without anaerobic digestion, with cover crop soil incorporation and field application of raw cattle manure. Biogas scenarios resulted in decreased global warming impacts of (1) 250 and (2) 120 Mg CO2eq for a 1000-hectare example dairy farm due to substitution of natural gas. However, emissions from ensiling, biogas plant operation, and agronomic effects increased other environmental impacts. Agronomic modelling with the Daisy model showed a crop yield increase of 0.11 Mg DM ha⁻¹ year⁻¹ on a sandy loam soil with cover crop digestion, but also an increase in N leaching of 38% and a decrease in soil C stocks of 8.1 Mg C ha⁻¹ over 100 years relative to the reference. Emissions of VOCs and NOx during ensiling increased ozone formation and negative impacts on human health and ecosystems, although further research is needed to better understand these emissions. In conclusion, this modelling study shows that greenhouse gas emissions can be reduced by using ensiled cover crops for co-digestion with manure when biogas is used to substitute fossil gas, although trade-offs with other environmental categories must be considered.
... It concludes that low-carbon leaders such as California and the European Union have followed a policy sequence that helps overcome some of the political challenges low-carbon policy faces by building economic interest groups to support decarbonization and reducing the costs of technologies required for cutting emissions. While politically effective, this policy pathway faces environmental and cost-effectiveness challenges, including excess rent capture and lock-in.Other policies are addressed bySteurer (2010),Plevin, Delucchi, and Creutzig (2014), andMarkard, Raven, and Truffer (2012).Steurer (2010) analyzes the role of governments in promoting corporate social responsibility (CSR) to characterize public policies related to CSR in Europe, including regulatory approaches, incentives, voluntary initiatives, and partnerships with businesses and other stakeholders.Plevin, Delucchi, and Creutzig (2014) evaluate the use of Attributional Life Cycle Assessment (ALCA) as a tool for estimating climate-change mitigation benefits and their implications. Given that ALCA is not predictive of real-world impacts on climate change, a conceptually superior approach, namely consequential LCA (CLCA), avoids many of its limitations. ...
... Delucchi, and Creutzig (2014), andMarkard, Raven, and Truffer (2012).Steurer (2010) analyzes the role of governments in promoting corporate social responsibility (CSR) to characterize public policies related to CSR in Europe, including regulatory approaches, incentives, voluntary initiatives, and partnerships with businesses and other stakeholders.Plevin, Delucchi, and Creutzig (2014) evaluate the use of Attributional Life Cycle Assessment (ALCA) as a tool for estimating climate-change mitigation benefits and their implications. Given that ALCA is not predictive of real-world impacts on climate change, a conceptually superior approach, namely consequential LCA (CLCA), avoids many of its limitations. However, because ...
Systematic knowledge about how the literature has dealt with the different dimensions of sustainability-bound industrial policies is still limited. The purpose of this article is to investigate the nature of this body of literature to suggest a frame of reference for further research on climate policy experiments. For that, a quantitative bibliometric analysis is combined with a narrative literature review. The quantitative study covers co-citation and keyword co-occurrence patterns from 1,660 articles published in Scopus and Web of Science from 1976 to 2023. The qualitative in-depth analysis covers 33 top-cited works. The quantitative study indicates three patterns: (1) a discussion about green industrial policies from a broad development perspective, (2) a focus on thematic specialization to investigate the role of industry and the State, and (3) contributions concerned with sustainable industrial development in a specific national context (mainly China). The qualitative analysis reveals a consensus on the importance of proactive State interventions. The most cited and discussed instruments are of a regulatory nature (carbon pricing) and tax incentives, but with strong differences in the breadth and scope of State intervention. The article concludes that effective decarbonization industrial policies demand concerted State capabilities strictly and pertinently aligned to the peculiar features of different sustainability challenges.
... ALCA is less complicated and suitable for assessing immediate environmental performance (Finnveden et al 2009). Although ALCA has primarily been used for policy decisions, Plevin et al (2014) argue that the approach may overlook critical consequential impacts. To address these limitations, it is recommended to combine ALCA and CLCA: ALCA to identify impact categories and CLCA to analyze large-scale impacts. ...
Achieving global carbon neutrality by 2050 requires substantial decarbonization of the built environment, with LCA playing a critical role in evaluating buildings’ environmental impacts. Among the primary LCA methodologies, CLCA offers unique decision-support capabilities but faces limited adoption in the building sector, restricting its effectiveness. This study investigates the methodological challenges contributing to the low adoption of CLCA, focusing on issues such as goal and scope definition, consequential life cycle inventory (CLCI) modelling, and uncertainty analysis. A systematic review of 20 building-related CLCA studies was conducted using an adapted CLCA framework based on the step-wise process by Weidema et al (2009). Studies with strong alignment to the framework provided robust insights into decision contexts, market dynamics, co-products, and uncertainty analysis, enhancing transparency and replicability. Conversely, studies with significant gaps struggled with poorly defined decision contexts, insufficient data, and the omission of uncertainty analyses, reducing their reliability and applicability. This review underscores the growing potential of CLCA in sustainability assessments within the built environment. However, technological constraints, data limitations, and methodological complexities hinder its broader adoption and comparability. A tailored CLCA framework for the construction sector is proposed to address these gaps, incorporating decision trees, standardized templates, and uncertainty analysis guidelines to improve transparency, robustness, and decision-making support in achieving a low-carbon built environment.
... However, these results alone could not offer any insights on nutrient CE measures. Substitution approach in this instance can be deliberated despite the dispute on the methodological feasibility (Plevin et al., 2014;Schrijvers et al., 2020;Suh and Yang, 2014). When substitution is applied for secondary products from the treatment processes, additional information pertaining to the "avoided burden" is necessary for accuracy and representativeness. ...
Nutrient circularity, an exemplification of circular economy (CE), is situated in the waste/wastewater-agriculture nexus. Recycling nutrient elements from waste streams to fertilizer products amplify the sustainable management of resources and intersect technical and biological loops, a concept developed for CE. Such a complex system needs to be directed by robust assessment methods such as life cycle assessment (LCA) to identify trade-offs and potentials. This review aims to provide a comprehensive outlook of the current state of nutrient circularity and a critical analysis on the applicability of LCA to nutrient CE pathways. Our worked has summarized CE pathways including direct land application, traditionally integrated processes in wastewater treatment plants, and targeted nutrient recycling technologies. Despite the restrictions on inputs streams, recycling technologies demonstrated a relative low selectivity. LCA is a powerful instrument to guide nutrient circularity; however, system modeling settings can confine the applicability of LCA for CE pathways. Given that LCA studies can only partially capture the CE characteristics, a deliberate methodological selection of functional unit, allocation method and impact indicators is required for the specific CE aspect under investigation. Lower data scale limits the LCA ability to assess CE practices that requires systemic analyses. Hence, full scale assessment is of necessity since it incorporates potential gains and drawbacks from the material upscaling, process efficiency changes and possible industrial symbiosis. The findings of this review lay a robust groundwork for future research, pinpointing areas of focus in LCA modeling within nutrient circularity. This is particularly vital for the Global South to ensure knowledge transfer and prompt action.
... In particular, we would expect that expanding the scope to IAMs would have highlighted many different approaches capturing consequential aspects and/or addressing more scalerelated questions. However, we believe that LCA studies should also be mindful of these issues, and deploy tools to help address them (particularly as LCA-specific approaches to address many of these concerns do exist), and it is important to progress in the field of CDR LCA, given the legitimacy leant through the use of LCA and particular concerns that the common use of LCA as a simple comparison of climatic merit misleads policy makers (Plevin, Delucchi, and Creutzig 2014). Overcoming the challenges highlighted in this review would provide a clearer pathway to the level of CDR required, and help to achieve this in as efficient and sustainable manner as possible. ...
Life Cycle Assessment (LCA) methods are increasingly used for policy decision‐making in the context of identifying and scaling up sustainable carbon dioxide removal (CDR) interventions. This article critically reviews CDR LCA case‐studies through three key lenses relevant to policy decision‐making on sustainable CDR scale‐up, namely comparability across CDR assessments, assessment of the climatic merit of a CDR intervention, and consideration of wider CDR co‐benefits and impacts. Our results show that while providing valuable life cycle understanding, current practices utilize diverse methods, usually attributional in nature, which are CDR and time‐specific. As a result, they do not allow comprehensive cross‐comparison between CDRs, nor reveal the potential consequences of scaling up CDRs in the future. We suggest CDR LCA design requires clearer definitions of the study scope and goal, the use of more consistent functional units, greater comprehensiveness in system boundaries, and explicit baseline definitions. This would allow for robust assessments, facilitating comparison with other CDR methods, and better evidencing net climate benefits. The inventory should collect time‐dependent data on the full CDR life cycle and baseline, and report background assumptions. The impact assessment phase should evidence the climatic merits, co‐benefits, and trade‐offs potentially caused by the expanding CDR. Finally, to ensure a sustainable scale‐up of CDR, consequential analyses should be performed, and interpretation involves the comparison of all selected metrics and the permanence of carbon storage against a baseline scenario.
... Moreover, producing certain biofuels may require substantial amount of energy and resources, leading to GHG emissions that could negate biofuel advantages. Consequently, it is crucial to thoroughly assess the ecological ramifications of diverse biofuels and their production techniques to ascertain their potential effects on climate change [10,11]. To maximize the benefits of biofuels while mitigating their effect on climate change, policies must encourage eco-friendly biofuel production and promote the use of low-carbon transportation alternatives. ...
To move toward a new energy pool with low-carbon emissions, it is necessary to gradually substitute fossil fuels with cleaner sources of energy and biofuels. In this analysis, the environmental life cycle assessment of palm oil (PO) (first generation)-, used cooking oil (UCO) (second generation)-, and microalgae (third generation)-based biodiesel production is compared. The functional unit is per kg of biodiesel produced. The system boundary is from cradle to gate. SimaPro v9.4 is used for the analysis using Ecoinvent v3.6 database. IMPACT 2002+ method is utilized for impact assessment. The research shows that the first-generation biofuel (palm oil) has more greenhouse gas (GHG) emissions than second-generation (UCO) biofuel, 5.35 kg CO2 eq., and 0.73 kg CO2 eq., respectively. The third-generation biofuel has the highest GHG emission, 5.47 kg CO2 eq. However, there was an increase in acidification for the PO biodiesel (20%) compared to microalgae biodiesel. This indicates that the decisions when defining the system boundary and functional units are sensitive to a set of variables.
... The outcomes of a carbon footprint calculation of a transportation fuel can vary depending on the methodological choices and assumptions made in the calculation. For biofuels, the modelling of the impacts associated with the land that the biomass is cultivated on -also known as land use changes (LUC) -can drastically change the GHG performance of the fuel (Barnabe et al., 2013;Creutzig et al., 2015;Plevin et al., 2014;Repo et al., 2015;Searchinger et al., 2022;Valin et al., 2015). For other fuel types, the type of electricity or heat used in the fuel production can be of particular relevance. ...
Various regional and international standards have been developed to measure the environmental impacts of transportation fuels and minimize greenwashing and misinformation regarding their sustainability. These frameworks offer standardized methods and calculation guidelines for fuel producers to be able to verify compliance with predefined sustainability criteria and to achieve greenhouse gas emission reduction targets. However, significant inconsistencies exist among these standards in terms of methods, calculation rules, and default values assigned to specific fuels. This study reviews and analyses five fuel standards, namely the European Renewable Energy Directive, the United Nation’s Carbon Offsetting and Reduction Scheme for International Aviation, the California Low Carbon Fuel Standard, the United States Renewable Fuel Standard, and the UK Renewable Transport Fuel Obligation. A qualitative analysis of the different schemes’ methods identified several discrepancies. These were found to be primarily related to the modelling approach used, the burdens and credits arising from different feedstock types and co-products, and the modelling of electricity and land use changes. An example of this is that different standards provide credits for certain waste types, such as animal manure in the RED and RTFO, or municipal solid waste in CORSIA. In addition to the qualitative analysis, the carbon intensity was calculated – according to the rules set out by these frameworks – for case studies of eight fuel types, including biofuels and electrolysis-based fuels. These calculations further highlighted how the use of different fuel standards can lead to conflicting assessments of a fuel’s environmental impact. Overall, our findings demonstrate substantial variations in the methods and calculation rules prescribed by the five standards, often resulting in markedly different carbon intensity scores for the same fuel. Based on this analysis, we propose specific changes to the calculation rules to enhance harmonization and improve the accuracy in reflecting the environmental consequences of fuel production and use. These recommendations include that indirect land use changes are always included, and more transparency regarding the methods for calculating the fuel carbon footprint.
... A two-step examination is often recommended for LCA studies involving both Attributional and Consequential LCAs (ALCA and CLCA, respectively) (Brander et al., 2019). In this comparative study, ALCA, which is the most common LCA approach was selected and conducted as the first step (Plevin et al., 2014). ALCA is often employed to compare multiple systems delivering the same service and is useful for locating hotspots with the greatest environmental impacts (Pedinotti-Castelle et al., 2019). ...
... The main environmental impact category considered was climate change, considering the interests of the project partners and the approach of WEDISTRICT. Moreover, academic literature from various disciplines and applications considers climate change as the key element to be analysed during an LCA [29][30][31][32][33][34][35][36][37][38]. Nevertheless, the results regarding seven other impact categories were also considered, as these are deemed of deep interest: photochemical ozone formation [39][40][41], acidification [42,43], eutrophication-terrestrial [44,45], land use [46][47][48], water use [49][50][51], resource use-fossils [52,53], and resource use-minerals and metals [54,55]. ...
The energy sector is essential in the transition to a more sustainable future, and renewable energies will play a key role in achieving this. It is also a sector in which the circular economy presents an opportunity for the utilisation of other resources and residual energy flows. This study examines the environmental and social performance of innovative energy technologies (which contribute to the circularity of resources) implemented in a demonstrator site in Luleå (Sweden). The demo-site collected excess heat from a data centre to cogenerate energy, combining the waste heat with fuel cells that use biogas derived from waste, meeting part of its electrical demand and supplying thermal energy to an existing district heating network. Following a cradle-to-gate approach, an environmental and a social life cycle assessment were developed to compare two scenarios: a baseline scenario reflecting current energy supply methods and the WEDISTRICT scenario, which considers the application of different renewable and circular technologies. The findings indicate that transitioning to renewable energy sources significantly reduces environmental impacts in seven of the eight assessed impact categories. Specifically, the study showed a 48% reduction in climate change impact per kWh generated. Additionally, the WEDISTRICT scenario, accounting for avoided burdens, prevented 0.21 kg CO2 eq per kWh auto-consumed. From the social perspective, the WEDISTRICT scenario demonstrated improvement in employment conditions within the worker and local community categories, product satisfaction within the society category, and fair competition within the value chain category. Projects like WEDISTRICT demonstrate the circularity options of the energy sector, the utilisation of resources and residual energy flows, and that these lead to environmental and social improvements throughout the entire life cycle, not just during the operation phase.
... In this regard, clear ISO guidance has not so far been defined [35]. The question whether policies should rely on attributional or consequential approaches is still debated [36][37][38]. For instance, while the RED II acknowledges that the substitution approach is appropriate for policy analyses, it favours an attributional approach for the regulation of individual economic operators and individual consignments of transport fuels (with some exceptions like considering the rigidity of some inputs such as waste). ...
... Although the differences seem small, the application of the two modes to one case study (which can actually not be done, because they basically address different questions) may give significantly different results, not only between CLCA and ALCA but also between different (scenario) assumptions within CLCA (see Schmidt 2010). Bearing in mind that ALCA and CLCA can result in potentially significant differences, Plevin et al. (2014a) recently argued that "using ALCA to estimate climate-change mitigation benefits misleads policy-makers" basically claiming that CLCA is conceptually superior to ALCA for supporting robust decision-making. Plevin et al. received a lot of criticism (Anex and Lifset 2014;Brandão et al. 2014;Dale and Kim 2014;Hertwich 2014;Plevin et al. 2014b;Suh and Yang 2014;Plevin et al. 2014c), but the debate has not been cleared yet, if ever (Baitz 2017;Prox and Curran 2017). ...
This chapter gives an overview of the mainstream method of life cycle assessment (LCA) on the basis of the generally accepted principles as laid down in the International Organization for Standardization (ISO) series of standards on LCA. The first part is devoted to the key questions addressed by LCA and sketches the historical development toward that method. The second part provides an overview of the LCA method itself, while the third part discusses some examples of LCA applications. Finally, the fourth part discusses some of the future challenges to LCA including life cycle sustainability assessment (LCSA) and streamlined LCA techniques.
... A main and widely accepted distinction between the attributional and the consequential approaches is that the former uses average data while the latter uses marginal data (Ekvall et al., 2005;Finnveden et al., 2009;Plevin et al., 2014;Sandén & Karlström, 2007;Schaubroeck et al., 2021). ...
Most life cycle assessment (LCA) studies use the attributional methodology. This approach attributes a share of global environmental impacts to one or multiple functions provided by a normatively circumscribed system. Multifunctional systems that are not technologically subdivisible between co‐functions are frequently encountered in LCA studies. It then becomes necessary to resort to co‐production modeling techniques, like the substitution approach. The use of substitution modeling in attributional LCA (ALCA) is, however, discouraged amongst practitioners, due to the alleged violation of central requirements of the attributional methodology. The objective of this research is to shed light on common misconceptions about the compatibility of substitution with ALCA. The first misconception is that the use of substitution in ALCA violates the conservation of total environmental impacts. We find that this idea arises from a confusion regarding the attribution of impacts to the secondary product(s). The second misconception stipulates that substitution is not coherent with the state‐descriptive characteristic of ALCA. We conclude that we can describe a given system as resulting from an inferred (substitution) change, rather than as disrupted by this change. Finally, we discuss the choice of the substituted technology, and argue there is a logic to marginal substitution in ALCA. We therefore recommend accepting substitution modeling in ALCA.
... As an example for the food system, Springmann et al. (2017;2018) assess how taxes on specific food products could reduce climate and health impacts, especially in high-meat consumption regions. Having robust estimates of environmental footprint and recognizing the limitations of this approach would be essential for a sound implementation (Plevin et al. 2014). ...
The world is in the midst of a triple planetary crisis of climate change, biodiversity loss and pollution and waste. The global economy is consuming ever more natural resources, while the world is not on track to meet the Sustainable Development Goals.
The scientific community has never before been more aligned or more resolute on the need for urgent global transformation towards the sustainable use of resources. This 2024 edition of the Global Resources Outlook sheds light on how resources are essential to the effective implementation of the Agenda 2030 and multilateral environmental agreements to tackle the triple planetary crisis. The report brings together the best available data, modelling and assessments to analyse trends, impacts and distributional effects of resource use. It builds on more than 15 years of work by the International Resource Panel, including scientific assessments and inputs from countries, a vast network of stakeholders in the field and regional experts.
The report illustrates how, since the 2019 edition of this report, rising trends in global resource use have continued or accelerated. The report also shows how demand for resources is expected to continue increasing in the coming decades. This means that, without urgent and concerted action, by 2060 resource extraction could rise by 60% from 2020 levels – driving increasing damage and risks.
However, this fate is not sealed. The report also describes the potential to turn negative trends around and put humanity on a trajectory towards sustainability.
For that, bold policy action is critical to phase out unsustainable activities, speed up responsible and innovative ways of meeting human needs and create conditions conducive to social acceptance and equity within the necessary transitions. This includes urgent action to embed resources in the delivery of multilateral environmental agreements, define sustainable resource use paths and roll out appropriate financial, trade and economic incentives. The pathway towards sustainability is increasingly steep and narrow, and the window of opportunity is closing. The science is clear: The key question is no longer whether a transformation towards global sustainable resource consumption and production is necessary, but how to make it happen now. Addressing this reality, based on evolving concepts of a just transition, is an essential part of any credible and justifiable way forward.
... As an example for the food system, Springmann et al. (2017;2018) assess how taxes on specific food products could reduce climate and health impacts, especially in high-meat consumption regions. Having robust estimates of environmental footprint and recognizing the limitations of this approach would be essential for a sound implementation (Plevin et al. 2014). ...
... These interactions and spillovers across different time horizons and spatial scales point to the multidimensionality of equity and suggest that in many cases, it may be more productive to approach equity "on a spectrum of getting 'more/ less' rather than an absolute 'is/is not'" (32). Although it is not always possible to model these interactions explicitly, the examples in SI Appendix, section S5 underscore the value of contextualizing the implications of the specific spatial and temporal bounds of analysis and acknowledging the potential limitations of these system boundary choices (29,111). ...
Equity is core to sustainability, but current interventions to enhance sustainability often fall short in adequately addressing this linkage. Models are important tools for informing action, and their development and use present opportunities to center equity in process and outcomes. This Perspective highlights progress in integrating equity into systems modeling in sustainability science, as well as key challenges, tensions, and future directions. We present a conceptual framework for equity in systems modeling, focused on its distributional, procedural, and recognitional dimensions. We discuss examples of how modelers engage with these different dimensions throughout the modeling process and from across a range of modeling approaches and topics, including water resources, energy systems, air quality, and conservation. Synthesizing across these examples, we identify significant advances in enhancing procedural and recognitional equity by reframing models as tools to explore pluralism in worldviews and knowledge systems; enabling models to better represent distributional inequity through new computational techniques and data sources; investigating the dynamics that can drive inequities by linking different modeling approaches; and developing more nuanced metrics for assessing equity outcomes. We also identify important future directions, such as an increased focus on using models to identify pathways to transform underlying conditions that lead to inequities and move toward desired futures. By looking at examples across the diverse fields within sustainability science, we argue that there are valuable opportunities for mutual learning on how to use models more effectively as tools to support sustainable and equitable futures.
... The necessary engagement of policymakers and stakeholders is still missing in dynamic LCA (Adhitya et al., 2011;Francis and Thomas, 2023;Plevin et al., 2014;Yang and Campbell, 2017). Papacharalampopoulos et al. (2022) proposed a model to include dynamic LCA in decision support and policymaking levels. ...
DLCA has been applied to several food waste streams, however, to date no critical assessment of its strengths, weaknesses, opportunities, and threats (SWOT) is available in the scientific literature. Accordingly, the present review aims to provide a comprehensive overview of the available literature on DLCA and its application to HCFW by providing critical assessment and perspectives for future research. The Population, Intervention, Comparison, and Outcome (PICO) framework for literature review was employed, with just 12 relevant studies identified between 1999 and 2022, highlighting a dearth of research on DLCA of food waste and the need for further research. Identified studies exhibit significant variations with respect to DLCA methodology, boundary settings, and data quality and reporting, with more attention typically given to combining conventional LCA with dynamic characterization models, thus making it difficult to draw conclusive findings or identify consistent trends. Additionally, most identified studies employed DLCA for a specific case study and comparison with traditional LCA outcomes was typically ignored; just one study presented the projected impact from both LCA and DLCA for the entire life cycle of a product. Employed functional/reference units ranged from specific quantities such as 1 kg of refined crystals or syrup, 1 g L−1 Sophorolipid solution, and 1 kg of dry food with packaging material, to broader indicators like 1 kg of biofuel or 1 MJ of primary energy. Monte Carlo simulation was the most frequently employed method for uncertainty analyses within identified studies. Sensitivity analyses were conducted in just 4 studies, but it was not always clearly reported. While DLCA is undoubtedly a more realistic approach to impact assessment, and thus likely more accurate, a need exists for increasingly standardized and regulated versions of DLCA for global and multi-criteria practices.
... 42 In addition to these conceptual and methodological problems, GWPs introduce strong time preferences into these comparisons. 6,[43][44][45][46][47] Another issue with the verifiability of LCA is how to define a baseline which is often necessary for determining avoided emissions in sequestration and inventory accounting. The least contentious baseline in inventory accounting is the inventory at the start of accounting. ...
Carbon accounting without life cycle analysis (LCA) is possible by requiring one ton of sequestration for each extracted ton of carbon. A carbon takeback obligation eliminates the need to track carbon through the supply chain.
... Another methodological issue is the risk of violating mass balance by mixing attributional and consequential approaches (Bo Weidema, 2013). Still, Plevin et al. (2014) claim that the consequential approach is needed because the attributional would mislead policymakers. The debate might have had an impact on 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t the originally attributional EN 15804, as it allows reporting the benefits outside the system boundaries, in the separate module D. The data reported in module D is not commensurable and has no impact to the product system under study which seems to provide methodologically feasible consensus in the case of upstream recycling. ...
Due to the heavy environmental impacts on the building industry, wood-based building materials are gaining interest. They may improve the indoor climate and have a low carbon footprint compared to steel and concrete structures. This study provides knowledge on the carbon footprint of wood shavings and wood shavings improved with clay as insulation materials. The study defines the lifecycle emissions of five different wall structures, of which two are of conventional type in the Finnish context and three with wood shavings as insulation. The study follows the EN standards on buildings’ life cycle assessment with a streamlined approach and discusses the applicability of the method in the normative context. The study analyzes multiple methodological aspects, including biogenic carbon, co-product allocation, and defining the functional unit in wall structure comparison. In the base case, the exterior wall using wood shaving as insulation provided the lowest GHG emissions of the compared structures. The study finds global warming potential of wood shavings moderately sensitive to allocation choices and energy sources used in the drying of wood shavings with clay, while the End-of-Life treatment option can radically change the results in biogenic global warming potential. From the perspective of applying the buildings’ life cycle assessment in the normative context, there is a call for further research for controlling uncertainties in modeling End-of-Life options of biogenic materials.
... Therefore, attributional data is ideally coupled with producer-specific LCI data [72], as was done in this study. However, arguments have been made that consequential approach should be preferred [73,74], as attributional allocation is not able to predict the impacts implementing the studied system would have. Consequential studies seek to identify and quantify the market impact of the studied process, requiring LCI data for marginal changes. ...
As sustainable development increases its significance in policy-making, methods for quantifying the sustainability of a project become more important. One such method is life-cycle assessment (LCA). In this study, an LCA assessment of a radiant cooling system was conducted for a retrofit project of a small office building. The studied building is located in Sant Cugat in north-eastern Spain. The radiant cooling system was also compared with a conventional alternative, an all-air variable air volume system. The goal of the study is to provide a generalisable methodology for conducting an LCA-assessment in a retrofit project involving cooling. The methodology of the assessment consists of two parts. Building energy models in IDA-ICE 4.8 were used to determine the energy use of the systems and the resulting thermal comfort conditions in the building, while SimaPro 9.4 was used to carry out the LCA assessment. A major novelty in the study is the use of thermal comfort as the functional unit for the LCA assessment. The results show that the radiant system has a lower environmental impact in all ReCiPe2016 midpoint impact categories during the systems' estimated lifetime of 50 years. However, a sensitivity analysis revealed that while the radiant system's environmental impact is mainly dependent on the manufacturing process, the conventional system's impact is largely determined by its operational energy use. Therefore, the conventional system is significantly more sensitive to decarbonisation of electricity production.
... The considerable water and carbon footprints of dairy production, as estimated using attributional approaches that estimate the impacts associated with current production, have resulted in calls for reductions in dairy consumption to reduce the environmental impacts of consumer consumption (Poore and Nemecek 2018;Berners-Lee 2020;Marinova and Bogueva 2020;Kovacs et al. 2021). However, attributional footprints are not suitable to be used to inform decisions because they do not consider the consequences of changes to a system (Plevin et al. 2013;Perry 2014;White and Hall 2017;Simmons et al. 2020). For example, organic food has a lower carbon footprint than conventionally grown food but the consequences of a move to organic agricultural production in England and Wales would increase the climate change impacts of food production (Smith et al. 2019). ...
Context
Climate change and water scarcity are global challenges facing humanity. Animal agriculture generates considerable greenhouse gas (GHG) emissions and consumes large volumes of water from rivers, streams and lakes. Reducing consumption of animal agricultural products with a relatively high carbon or water footprint, such as dairy, is often promoted as a mechanism to reduce the environmental impacts of food production. Attributionally-based footprints do not, however, assess the consequences of a change in demand for a product.
Aims
This study aimed to assess the water and climate change consequences of replacing NSW dairy production, and co-products of dairy production, with plant-based alternatives.
Methods
Process-based consequential life cycle assessment was used.
Key results
Water savings associated with the change would be limited and GHG emissions reductions would be ~86% of that as estimated by the carbon footprint of production. When NSW dairy production was replaced with soy-based alternatives and two GHG emissions reduction strategies were implemented across the industry, namely enteric methane inhibitors and flaring methane from effluent ponds, GHG emissions increased by 0.63 Mt carbon dioxide equivalent when dairy production was replaced.
Conclusions
The environmental benefits associated with replacing NSW dairy production with plant-based alternatives should not be determined by attributionally-based approaches.
Implications
Policies that aim to reduce the environmental impacts of agricultural production need to consider the market effects of a change in demand for products and not rely on estimated impacts of current production.
... 1.3] (Ivanova et al., 2017;Steininger et al., 2018). Dies macht die notwendige komparative Bewertung von Alternativen methodisch äußerst komplex und hat zu einer Ausdifferenzierung verschiedener Methoden und wissenschaftlicher Communities geführt (Guinée et al., 2011;Heinonen et al., 2020;Ivanova et al., 2020;Matuštík & Kočí, 2021 -Najafabady et al., 2021;Earles & Halog, 2011;Keen, 2021;Pauliuk et al., 2017;Plevin et al., 2014). 5. Einsparungen von Zeit und/oder Geld durch alternative Handlungsoptionen führen oft zu Rebound-Effekten ("Jevons Paradoxon"): Wird eingespartes Geld oder Zeit emissionsintensiv verwendet, führt das zu einer direkten oder indirekten Problemverlagerung sowie zu geringeren Emissionseinsparungen als erwartet. ...
Zusammenfassung
Teil 2 gibt einen umfassenden Überblick über alle Lebensbereiche, indem die Klimaauswirkungen verschiedener Handlungsfelder analysiert werden. Kapitel 3 bietet einen Überblick über diese Handlungsfelder und ihre Verflechtungen. Untersucht werden die Klimawirkungen in den Bereichen Wohnen, Mobilität und Ernährung sowie für die Handlungsfelder Erwerbsarbeit, Versorgung, Betreuungs- und Pflegearbeit und die frei verfügbare Zeit für Erholung und soziale Aktivitäten. Um die in Paris beschlossenen Klimaziele zu erreichen, sind Veränderungen im Alltag der Menschen und in ihrem täglichen Verhalten notwendig. Diese Veränderungen können nicht primär durch Appelle an die Eigenverantwortung ausgelöst werden. Vielmehr bedarf es geeigneter Strukturen wie Regulierung, steuerliche Anreize, infrastrukturelle Veränderungen und Verbote sowie Zeit, um Aktivitäten mit hohen Emissionen zu begrenzen bzw. solche mit geringen Emissionen zu erhöhen. Klimafreundliche Strukturen sind notwendig, um klimafreundliches Handeln leichter in den Alltag zu integrieren und eine attraktive Alternative zu bestehenden, nicht nachhaltigen Praktiken zu bieten.
... The life cycle concept has gained widespread acceptance as a model for evaluating the environmental impact of goods and services. As a result, LCA is often used to refer to the climate change mitigation advantages of alternative goods and services [16] [17]. When considering the environmental benefits associated with an insulator's life cycle, it is necessary to conduct proper evaluations to ensure that the impacts associated with the phases of production and disposal are offset by the benefits associated with the use phase, such as energy and carbon dioxide (CO2) emission savings [18]. ...
The European Union aims to reduce greenhouse gases emissions by 80–95% compared to 1990 levels by 2050. Therefore the life cycle concept has gained widespread acceptance as a model for evaluating the environmental impact of goods and services. In this study, the optimal thickness of various insulation materials for external walls, roofs, and floors using a Mediterranean climate zone's hot summers and mild winters for a hypothetical residential building for four cardinal orientations was determined. The criteria for determining the optimum thickness represent a turning point in terms of cooling energy consumption (electricity). The optimum thickness of nine different types of insulation materials was defined using the aforementioned approach. These materials included aerogel, polyisocyanurate, polyurethane, extruded polystyrene, expanded polystyrene, phenolic foam, cellulose fiber (cellulose), mineral wool, and glass wool (GW). The purpose of this paper is to calculate the carbon payback time (CPBT) using the cradle-to-gate life cycle assessment method by considering the global warming potential (GWP) of insulation materials at their optimum thickness. The CPBT is calculated as the ratio of the total building's GWP to the GWP of savings from cooling and heating (electricity and natural gas). The results indicated that when evaluating the average CPBT for four cardinal orientations (FCO), aerogel has the longest CPBT of 2.34 years, and GW has the shortest CPBT of just 0.09 years. Aside from cost payback time, the findings of this study provide a new perspective on selecting appropriate thermal insulation.
... An advantage of solution 1 (specifically the requirement in paragraph 2) is that it addresses broader limitations with attributional inventories, in particular, the limitation that attributional inventories do not reflect the total change in emissions, either positive or negative, caused by the reporting entity's actions (Plevin et al. 2014;Brander et al. 2019;Brander 2022a): ...
Purpose
Market-based GHG accounting allows companies to report their emissions based on the purchase of emission attributes. This practice is widespread for reporting ‘scope 2’ electricity emissions and has recently been proposed for both ‘scope 1’ (direct) and ‘scope 3’ (other value chain) emission sources. However, the market-based method has been criticised for undermining the accuracy of GHG disclosures, and it is therefore highly important to explore the requirements for accurate GHG inventories and the solutions to market-based accounting.
Methods
This paper uses two methods: firstly, thought experiments are used to identify principles for accurate corporate GHG inventories and, secondly, formal prescriptions are developed for possible solutions to market-based accounting.
Results and discussion
The findings identify six principles for accurate corporate GHG inventories, which are then used to inform the development of two possible solutions. The first solution is to report changes in emissions caused by company actions separately from the GHG inventory, including any changes caused by the purchase of emission attribute certificates. The second solution proposes a causality requirement for the use of emission attributes in GHG inventories. Although the analysis focuses on corporate or organisational GHG inventories, the principles and solutions apply equally to attributional product carbon footprinting and life cycle assessment more broadly.
Conclusions
We emphasise that inventories are only one form of accounting method, and their accuracy should not be undermined by attempting to fulfil functions that are best served by other methods.
... In contrast, a consequential approach can assess the magnitude of potential environmental impacts associated with a change in demand for a product, including the consequences of this change on other product systems (Brandão et al., 2017). More details on the two methods can be found in various literature (Brandão et al., 2014;Plevin et al., 2014;Suh & Yang, 2014). This study aims to conduct an attributional LCA. ...
This study aims to evaluate the environmental impact of using red mud (RM) as a partial replacement for cement in concrete production. Using industrial byproducts such as red mud as a raw material in concrete can reduce the environmental impacts of concrete and alumina industries. Red mud can also provide a sustainable solution for its disposal problem, while also improving the durability and strength of concrete. Life cycle assessment methodology was applied using Simapro© software. A cradle-to-gate analysis was carried out. The results were analyzed based on the Ecoinvent 3.8 database and ReCiPe method for 18 impact categories. The results show that the use of RM in concrete production also had a significant positive impact on all environmental impact categories, including freshwater ecotoxicity and human carcinogenic toxicity, compared to traditional concrete production. On the other hand, disposing of RM in landfills had been analyzed and from the results RM disposal showed significant negative impacts on the environment, including human carcinogenic toxicity, freshwater eutrophication, and marine ecotoxicity. These reductions vary between 0.2% (water consumption category) and 939.7% (Human carcinogenic toxicity). This study presents a significant contribution to the aluminum and construction industries by shedding light on the possibility of utilizing RM as a sustainable raw material in concrete production, leading to a reduction in environmental impact. By analyzing the properties of various concrete samples containing different percentages of RM, this study also highlights the potential for enhancing the mechanical properties of concrete through the incorporation of RM in certain amounts.
... if they handled multi-functionality in their product systems, although this modeling choice has a considerable effect on LCA results of biochar systems [335]. A thorough discussion of these modeling choices is outside the scope of this review, although they are crucial for the interpretation of the results [361][362][363][364]. ...
Current fossil fuel-based economies must be entirely phased out to prevent further environmental damage to future generations. To achieve this, (i) low-carbon energy carriers and systems must be fully integrated into all global energy sectors, and (ii) unavoidable residual greenhouse gas (GHG) emissions must be removed from the atmosphere—with carbon dioxide removal (CDR) technologies—to reach net-zero CO2 and GHG emissions in the 21st century. Energy systems analysis is needed to develop
methodologies to evaluate potential low-carbon energy carriers, technologies, and systems.
This thesis is mainly motivated by (i) the lack of integrating environmental aspects during the design phase of low-carbon decentralized energy systems and (ii) the limited understanding of the life cycle environmental consequences of CDR technologies to
enable the subsequent removal of residual GHG emissions. Thus, the following question has to be addressed: “What are the implications of integrating life cycle assessment (LCA) in the design phase of low-carbon energy systems?”. In addition, questions have to be answered to increase the understanding of the environmental life cycle consequences of CDR technologies, such as: “What is the current status of CDR LCAs?” and “How
can current CDR LCAs be improved?”.
... A review of literature on the topic of C-LCA and A-LCA reveals a diverse range of perspectives on the advantages and disadvantages of these two methodologies. Studies by (Brandão et al., 2014;Dale and Kim, 2014;Ekvall, 2019;Hertwich, 2014;Plevin et al., 2014;Prapaspongsa and Gheewala, 2017;Schaubroeck et al., 2021;Zamagni et al., 2012) have all contributed to this discourse, highlighting various pros and cons associated with each approach. Despite this, it is worth noting that the aviation sector similar to the shipping sector adopted a process-based attributional LCA approach along the whole aviation fuel supply chain (ICAO, 2019). ...
This research was motivated to address limitations in the current lifecycle assessment frameworks with the absence of proper guidelines for developing default lifecycle values of energies in consideration of supply chain activities and maritime transportation. Given this, it aims to evaluate the level of life cycle GHG emissions of heavy fuel oil, LNG, LPG and methanol as marine fuels produced and supplied in energy import-dependent countries, using South Korea as a case study. The analysis clearly shows that the impact of international shipping on Well-to-Tank (WtT) GHG emissions for energy carriers would be subject to several factors: propulsion system types, the quantify of energy transported, and the routes and distances of voyages. For instance, transportation emissions from LNG carriers for LNG fuel vary significantly depending on the country of import, ranging from 2.26 g CO2 eq./MJ (representing 12.2 % of Well-to-Tank (WtT) emissions for Malaysia) to 5.97 g CO2 eq./MJ (representing 33.3 % of WtT emissions for Qatar). As a preliminary study, an enhancement on the quality of the input/inventory data is imperative for obtaining a reliability of results. Nevertheless, the comparative analysis of different fuels and life stages provides valuable insights for stakeholders to develop effective policies and energy refueling plans for reducing life cycle GHG emissions from marine fuels. These findings could also enhance the current regulatory framework and provide meaningful lifecycle carbon footprints of marine fuels for energy importing countries. The study results also strongly suggest that default values of GHG emission for different countries relying on energy imports via international maritime transport should be further developed in consideration of the impact of regional differences, such as distance, from the importing country for successful arrival of LCA application on marine industry.
... Finally, concerning consistency, a major issue for ALCA is the lack of life cycle impact assessment methods that partition environmental processes and respect the additivity rule (see Section 3.5.1 in the study by Schaubroeck et al., 2021b). However, the possible inconsistency in data and data quality (e.g., for process X, methane emission amounts are covered, but this is not the case for process Y, even though methane emissions are reported) should also be kept in mind (Plevin et al., 2014) and may be regarded as insurmountable. However, this is applicationdependent per case study. ...
Life cycle assessment (LCA) is an essential tool for assessing the environmental impact of product systems. There are two main types: attributional LCA (ALCA), which assesses the global impact share of a product's life cycle, and consequential LCA (CLCA), which evaluates the consequential impact of a decision. In our analysis, we explored the relevance of these types for society and their ability to aid decision-making. This analysis builds upon existing literature and incorporates two ideological and three pragmatic criteria. First, when it comes to realistic modeling as desired in the context of sustainable development, in theory, CLCA attempts to model realistically, whereas ALCA falls short to a certain degree because of conceptual rules, e.g., artificial splitting of co-product processes. Concerning the second criterion of alignment with ethics, CLCA completely aligns with consequential ethics, where an action is judged based on its consequences. This alignment of CLCA makes it undoubtedly relevant in a world where we aim to obtain favorable consequences in the future, e.g., meeting sustainability goals. ALCA is only partially consequential, as it is restricted by conceptual rules relating to deontological ethics and, for example, covers the relative past of the product. Since deontological ethics, i.e. judging an action based on its alignment with rules, is generally relevant for our modern human society, there is room for complementarity in ethical relevance between ALCA and CLCA. However, the conceptual rules of ALCA (e.g., additivity) and their relevance have not been accepted by society. As a result, ethical acceptance of ALCA is still required. In the context of decision support, CLCA evaluates the consequences of decisions, while ALCA encompasses the approval and sharing of potential responsibility for the environmental impact throughout the life cycle of the product associated with the decision. We also highlight the unique valorization of Organizational ALCA, which entails the aforementioned aspects for the organizations responsible for the product. Concerning the three practical criteria, the following conclusions were drawn. Although ALCA has received the most attention in terms of standards, only CLCA can currently be consistently conducted in a reliable manner. This is because the current life cycle impact assessment methods applied in ALCA do not yet partition environmental multi-input processes. CLCA should be given greater prominence in standards. Furthermore, the complexity and uncertainty associated with modeling may often be only slightly higher for CLCA than for ALCA, mainly due to the consideration of change resulting from a decision. However, both ALCA and CLCA modeling may be similarly complex and have equally high levels of uncertainty as both methods encompass past and/or future projections (e.g., prediction of future background processes). Finally, ALCA modeling may be viewed as a practical approximation of CLCA, but the current CLCA models are more suitable for studying consequential effects. As CLCA modeling and databases continue to improve, this distinction will become even more pronounced.
... While exhortations for the use of life cycle thinking and LCA can be found in many EU policy documents, the use of LCA as an integral component of policy implementation is largely limited to eco-labeling and the development of the product environmental footprint (PEF) (Sala et al., 2021). This is because LCA as a basis for policy decisions faces substantial challenges related to methodology and data (Astrup et al., 2018;Plevin et al., 2014;Watkins et al., 2017). For ecomodulation, commonly accepted approaches or definitions that are both sophisticated and simple enough to be widely used are needed (Watkins et al., 2017). ...
Extended producer responsibility (EPR) is an environmental policy strategy that makes producers responsible for the waste management of their products and packages. A key goal of EPR is to incentivize producers to (re)design their products and packages to improve their environmental performance, especially at end of life. However, because of the way in which the financial structure of EPR has evolved, those incentives have largely been muted or undetectable. Eco-modulation has emerged as an additional component in EPR to restore the missing incentives for eco-design. Eco-modulation operates through changes in the fees that producers pay to meet their EPR obligations. Eco-modulation includes both increased differentiation of types of products and associated fees, and additional bonuses and penalties-environmentally targeted discounts and penalties on the fees that each producer pays. Based on primary, secondary, and grey literature, this article characterizes challenges faced by eco-modulation if it is to restore the incentives for eco-design. These include weak linkages to environmental outcomes, fees too low to induce changes in materials or design, lack of adequate data and ex post policy evaluation, and implementation that differs across jurisdictions. Opportunities to address these challenges include use of life cycle assessment (LCA) to inform eco-modulation, increased eco-modulation fees, strategies to increase harmonization of eco-modulation implementation, mandated provision of data, and policy evaluation tools that establish the efficacy of different eco-modulation schemes. Considering the scope of the challenges and the complexity of establishing eco-modulation programs, we suggest treating eco-modulation at this stage as an experiment in promoting eco-design.
... During an attributional method, the potential environmental impacts of a product can be assessed in a descriptive way, in contrast, within a consequential approach, the magnitude of potential environmental impacts associated with a change in demand for a product, including the consequences of this change on other product systems (Brandão et al., 2017) can be assessed. More details on two methods can be found in various literatures (Brandão et al., 2014;Plevin et al., 2014;Dale & Kim, 2014;Suh & Yang, 2014). ...
Buildings are a basic requirement for human beings and an essential part of the built environment, with significant environmental impacts. In addition to their complex and diverse material use, buildings are expected to have a long lifespan, typically more than 50 years. This paper aims to evaluate the environmental performance of materials and construction activities for a typical residential building. Life cycle assessment methodology was applied using Simapro©software. A cradle-to-gate analysis was carried out. The results were analyzed based on the Ecoinvent 3.8 database and Eco-Indicator 99. The results show that reinforcing steel (21%) and concrete production (16%) are the most dominant processes, accounting for almost 37% of the overall environmental impact. Transportation also had an overall impact of around 15%. Brick production and use accounted for 11.23% of the overall impact, followed by lime mortar production (11%). Asphalt coating production and use had the 6th highest impact with 9.7% of the overall impact. Ceramic production accounted for 5% of the overall impact, followed by cut stone products with 3.58% of impact. Steel use, plaster mixing, excavation processes, laminate, fiberboard, paint, and glass production and use had around 7% of the overall impact in total. Besides, the resource depletion impact category showed the highest value among the three main impact categories. On the other hand, fossil fuels and respiratory inorganic impact categories were the most affected sub-impact categories among the 11 study impact categories. As material and designing codes, technology, and construction methods differ based on regions and countries, this paper demonstrates the importance of even smaller portions of materials such as Laminate production in the Land use and asphalt felt production in the Fossil fuels impact categories in, especially for countries with insufficient studies and databases for construction activities.
... Os resultados são convergentes para alguns combustíveis e práticas de manejo, mas ainda diferem bastante em outras. Há grande debate científico quanto às abordagens mais adequadas de acordo com cada especificidade (PLEVIN et al, 2014;ROSA et al, 2016). ...
The fashion system and industry are very important and strategic sectors for supporting the global economy, while at the same time causing one of a major environmental impact. Every day we see a growing concern in society about environmental issues, making necessary a rethink of production procedures in the textile and clothing industries. The fashion industry is primarily characterized by the product life cycle; labor exploitation; increasing consumption of non-biodegradable synthetic fibers such as polyester; unrestrained consumption and subsequent waste. This has led to a new paradigm marked by concern for various environmental issues, such as reducing water consumption, chemical usage, and energy, thereby striving to produce in a more sustainable manner. Concepts such as ethical fashion and sustainable fashion are currently leading scientific and industrial research in the search for new solutions with pre-consumption waste: natural and synthetic fibers and fabrics. In this manner, the objectives to be explored are intertwined with the potentials and resolutions within the fashion industry, pertaining to the advancement of their systems and their communication methods with consumers. Consequently, companies must reassess their strategies and reconsider their decisions, prioritizing new business models such as the “Circular Economy” as a competitive edge in the industry using the J. Gomes case study for this research.
Life-cycle assessment (LCA) is one of the most widely applied
methods for sustainability assessment. A main application of LCA is to compare alternative products to identify and promote those that are more environmentally friendly. Such comparative LCA studies often rest on, explicitly or implicitly, an idealized assumption, namely, 1:1 displacement between functionally equivalent products. However, product displacement in the real world is much more complicated, affected by various factors such as the rebound effect and policy
schemes. Here, we quantitatively review studies that have considered these aspects to evaluate the magnitude and distribution of realistic displacement estimates across several major product categories (biofuels, electricity, electric vehicles, and recycled
products). Results show that displacement ratios concentrate around 40−60%, suggesting considerable overestimation of the benefits of alternative products if the 1:1 displacement assumption was used. Overall, there have been a small number of modeling studies on realistic product displacement and their scopes were limited. Additional research is needed to cover more product categories and geographies and improve the modeling of market and policy complexities. As such research accumulates, their displacement estimates can form a database that can be drawn upon by comparative LCA studies to more accurately determine the environmental impacts of alternative products.
Circularity has emerged as a pivotal concept in the realm of sustainable resource management and business operations. Resource exhaustion and environmental degradation propelled by globalization and the culture of consumerism have intensified the focus on the concept of the circular economy around the world. Nevertheless, the evaluation and quantification of circularity achievements remain uncommon in corporate practices. This article employs a systematic literature review to delve into circularity measurements in the managerial life cycle. Key approaches emerging from the academic literature are examined, including life cycle costing, life cycle assessment, life cycle cost–benefit, life cycle benefit analysis, and life cycle sustainability assessment. The review seeks to offer a comprehensive overview of the methodologies employed to assess circularity in corporate processes, highlighting current challenges and opportunities for effective implementation. We adopt a conceptual model of sustainable and circular life cycle management based on specific performance indicators that allow the environmental, social, and economic impact of processes to be assessed throughout the life cycle of products or services. The implementation of Sustainable and Circular Life Cycle Management from a managerial perspective could support firms to eradicate and quantify waste, preserve the inherent value of products and materials, encourage the adoption of renewable energies, and eliminate harmful chemicals.
The principle of mathematical induction can be an effective tool in organizational decision making. Although these principles have the potential to increase efficiency, reduce uncertainty, and increase accuracy in organizational decision making, their application is limited and has not been fully exploited. Studies need to be conducted to bridge this gap by strengthening the understanding and application of the principles of mathematical induction in the context of organizational decision making. By considering the gaps that occur, it is necessary to conduct research on "The Principle of Mathematical Induction in Organizational Decision Making". This research provides an overview of how the principles of mathematical induction can bridge this gap and improve the quality of decision making in an organizational context. The research method used in this research is a qualitative approach and literature study which involves analysis of relevant literature related to the principles of mathematical induction in the context of organizational decision making. The conclusions from this research are: 1) Applying the principles of mathematical induction in organizational decision making can strengthen efficiency, reduce uncertainty, and increase accuracy in decision making; 2) In applying the principles of mathematical induction in organizational decision making, there are obstacles and challenges that need to be overcome; and 3) Utilizing the principles of mathematical induction involves the use of structured methods, in-depth analysis, and a more objective approach.
Atıksuda bulunan kirleticileri gidererek temiz çıkış suyu üretmek için tasarlanan ve inşa edilen atıksu arıtma tesisleri (AAT), kentsel sistemler için temel gereksinimdir. Söz konusu tesisler ham atıksuyun alıcı ortamlara deşarjı nedeniyle oluşabilecek çevresel etkilerin azaltılmasını sağlamaktadır. Buna karşılık, faaliyetleri sürecinde gerek kaynak tüketimleri (su, elektrik gibi) gerekse emisyon oluşturmaları (metan, nitroz oksit gibi) nedeniyle bu tesislerin çevresel açıdan sürdürülebilirliklerinin değerlendirilmesi önem taşımaktadır. Bu çalışmada, farklı özellikler taşıyan bir adet biyolojik (klasik aktif çamur prosesi) ve bir adet ileri biyolojik (A2/O prosesi) atıksu arıtma tesisinin işletilmesi sürecinin karbon ayak izi yaşam döngüsü yaklaşımı ile hesaplanmış ve karşılaştırılmıştır. Karbon ayak izi, yaşam döngüsü değerlendirmesi (YDD)’nde küresel ısınma potansiyelinin (KIP) bir göstergesidir. Çalışma kapsamında SimaPro 9.2 yazılımı ve IPCC 2013(100a) etki değerlendirme metodu kullanılmıştır. Gerçekleştirilen etki değerlendirme sonucunda, A2/O prosesine sahip atıksu arıtma tesisinin küresel ısınma potansiyeli 1,64 kg CO2 eşd/m3.atıksu, klasik aktif çamur prosesine sahip atıksu arıtma tesisinin küresel ısınma potansiyeli ise 1,23 kg CO2 eşd/m3.atıksu olarak hesaplanmıştır. Envanter analizi sonuçları araştırıldığında, değerlendirmenin yapıldığı atıksu arıtma tesislerine bağlı ortaya çıkan KIP etkisinin metan (CH4) ve nitroz oksit (N2O) emisyonları ile ilişkili olduğu belirlenmiştir. Arıtma tesisi ünitelerinin KIP üzerindeki etkileri karşılaştırıldığında, biyolojik arıtma ünitesinin KIP üzerindeki katkısının en yüksek olduğu belirlenmiştir. Atıksu arıtma tesislerinin işletilmesi sürecindeki proseslerin (su geri kazanımı, arıtma çamuru bertarafı, direkt sera gazı oluşumu, arıtılmış atıksuyun alıcı ortama deşarjı, kimyasal madde tüketimi, nakliye ve elektrik tüketimi) etkileri değerlendirildiğinde ise arıtma çamuru bertarafı için seçilen yöntemin ve elektrik tüketiminin küresel ısınma potansiyeli etki kategorisi üzerinde önemli ve belirleyici olduğu tespit edilmiştir.
The life cycle of a product is comprised of three broad stages:
(1) Production, including the extraction of raw material from the ground and conversion of materials into usable form; (2) Use, including the conversion of energy; and (3) Disposal, which can include recycling and/or landfill. This life cycle is often termed ‘cradle to grave’. Life cycle assessment (LCA) is a quantitative
technique used to assess the environmental performance of products (including service systems) over the full life cycle. The LCA technique is used to identify environmental performance
opportunities and to manage environmental risks associated with a product or service system. This chapter explores the history of LCA, the key principals of undertaking LCA, and methodological aspects of LCA with a focus on applications in the aviation sector. The chapter concludes with a review of LCA trends and an outlook of how LCA can contribute to sustainability in the aviation sector.
Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr−1 in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m−2 with 90% uncertainty bounds of (+0.08, +1.27) W m−2. Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m−2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial-era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m−2 with 90% uncertainty bounds of +0.17 to +2.1 W m−2. Thus, there is a very high probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m−2, is the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short-lived species that may either cool or warm climate. Climate forcings from co-emitted species are estimated and used in the framework described herein. When the principal effects of short-lived co-emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy-related sources (fossil fuel and biofuel) have an industrial-era climate forcing of +0.22 (−0.50 to +1.08) W m−2 during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short-lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial-era climate forcing by all short-lived species from black-carbon-rich sources becomes slightly negative (−0.06 W m−2 with 90% uncertainty bounds of −1.45 to +1.29 W m−2). The uncertainties in net climate forcing from black-carbon-rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co-emitted organic carbon. In prioritizing potential black-carbon mitigation actions, non-science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near-term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black-carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.
Environmental life cycle assessment is often thought of as cradle to grave and therefore as the most complete accounting of the environmental costs and benefits of a product or service. However, as anyone who has done an environmental life cycle assessment knows, existing tools have many problems: data is difficult to assemble and life cycle studies take months of effort. A truly comprehensive analysis is prohibitive, so analysts are often forced to simply ignore many facets of life cycle impacts. But the focus on one aspect of a product or service can result in misleading indications if that aspect is benign while other aspects pollute or are otherwise unsustainable. This book summarizes the EIO-LCA method, explains its use in relation to other life cycle assessment models, and provides sample applications and extensions of the model into novel areas. A final chapter explains the free, easy-to-use software tool available on a companion website. (www.eiolca.net) The software tool provides a wealth of data, summarizing the current U.S. economy in 500 sectors with information on energy and materials use, pollution and greenhouse gas discharges, and other attributes like associated occupational deaths and injuries. The joint project of twelve faculty members and over 20 students working together over the past ten years at the Green Design Institute of Carnegie Mellon University, the EIO-LCA has been applied to a wide range of products and services. It will prove useful for research, industry, and in economics, engineering, or interdisciplinary classes in green design. © 2006 by Resources for the Future. All rights reserved. All rights reserved.
Executive Summary
Bioenergy has a significant greenhouse gas (GHG) mitigation potential, provided that the resources are developed sustainably and that efficient bioenergy systems are used. Certain current systems and key future options including perennial cropping systems, use of biomass residues and wastes and advanced conversion systems are able to deliver 80 to 90% emission reductions compared to the fossil energy baseline. However, land use conversion and forest management that lead to a loss of carbon stocks (direct) in addition to indirect land use change (d+iLUC) effects can lessen, and in some cases more than neutralize, the net positive GHG mitigation impacts. Impacts of climate change through temperature increases, rainfall pattern changes and increased frequency of extreme events will influence and interact with biomass resource potential. This interaction is still poorly understood, but it is likely to exhibit strong regional differences. Climate change impacts on biomass feedstock production exist but if global temperature rise is limited to less than 2°C compared with the pre-industrial record, it may pose few constraints. Combining adaptation measures with biomass resource production can offer more sustainable opportunities for bioenergy and perennial cropping systems.
Biomass is a primary source of food, fodder and fibre and as a renewable energy (RE) source provided about 10.2% (50.3 EJ) of global total primary energy supply (TPES) in 2008. Traditional use of wood, straws, charcoal, dung and other manures for cooking, space heating and lighting by generally poorer populations in developing countries accounts for about 30.7 EJ, and another 20 to 40% occurs in unaccounted informal sectors including charcoal production and distribution.
This report provides the background for the two guidelines “The product, functional unit, and reference flows in LCA” (Weidema et al. 2003a) and “Geographical, technological and temporal delimitation in LCA” (Weidema 2003). It provides further documentation of the examples provided in these guidelines, as well as additional examples, further explanatory text, scientific background and reference to earlier methodological guidelines. It also expands on specific issues, which were not found to be of sufficient general interest to merit inclusion in the guidelines.
This report and the two guidelines that it supports, carry two key messages:
1. The fundamental rule to apply in all methodological choices in life cycle assessment is that the data used must reflect as far as possible the processes actually affected as a consequence of the decision that the specific life cycle assessment is intended to support. Thus, there is a close link between the goal or application area of the life cycle assessment and the methodological choices. This is elaborated in section 1.1.
2. Life cycle assessments, insofar as they deal with comparing potential choices between alternative products, rely heavily on market information, i.e. information on how the market affects the potential choices and how the markets will react to these choices.
Whenever possible, the above understanding has been converted to practical, step-by-step procedures for including market information when:
• defining the functional unit (chapter 3),
• defining the geographical and technological scope (chapter 4),
• handling co-products (chapter 5),
• forecasting data for processes taking place in the future (chapter 6).
For all these elements of the life cycle assessment methodology, the inclusion of market information leads to improvements, which also reduces the uncertainty of life cycle assessment results. While the methodological improvements are described in this report, the consequences for uncertainty are the topic of a separate report: "Reducing uncertainty in LCI. Developing a data collection strategy" (Weidema et al. 2003).
Purpose
The increasing concern for adverse effects of climate change has spurred the search for alternatives for conventional energy sources. Life cycle assessment (LCA) has increasingly been used to assess the potential of these alternatives to reduce greenhouse gas emissions. The popularity of LCA in the policy context puts its methodological issues into another perspective. This paper discusses how bio-electricity directives deal with the issue of allocation and shows its repercussions in the policy field.
Methods
Multifunctionality has been a well-known problem since the early development of LCA and several methods have been suggested to deal with multifunctional processes. This paper starts with a discussion of the most common allocation methods. This discussion is followed by a description of bio-energy policy directives. The description shows the increasing importance of LCA in the policy context as well as the lack of consensus in the application of allocation methods. Methodological differences between bio-energy directives possibly lead to different assessments of bio-energy chains. To assess the differences due to methodological choices in bio-energy directives, this paper applies three different allocation methods to the same bio-electricity generation system. The differences in outcomes indicate the importance of solving the allocation issue for policy decision making.
Results and discussion
The case study focuses on bio-electricity from rapeseed oil. To assess the influence of the choice of allocation in a policy directive, three allocation methods are applied: economic partitioning (on the basis of proceeds), physical partitioning (on the basis of energy content), and substitution (under two scenarios). The outcomes show that the climate change score is assessed quite differently; ranging from 0.293 kg to 0.604 kg CO2 eq/kWh. It is argued that this uncertainty hampers the optimal use of LCA in the policy context. The aim of policy LCAs is different from the aim of LCAs for analysis. Therefore, it is argued that LCAs in the policy context will benefit from a new guideline based on robustness.
Conclusions
The case study confirms that the choice of allocation method in policy directives has large influence on the outcomes of an LCA. With the growing popularity of LCA in policy directives, this paper recommends a new guideline for policy LCAs. The high priority of robustness in the policy context makes it an ideal starting point of this guideline. An accompanying dialog between practitioners and commissioners should further strengthen the use of LCA in policy directives.
We develop an analytical and numerical multi-market model that integrates land, fuel, and food markets, and link it with an emissions model to quantify the importance of carbon leakage relative to the intended emissions savings resulting from the Renewable Fuel Standard (RFS) for conventional biofuels. The expansion of biofuels mandated by the RFS can increase or decrease GHG emissions depending on the policy regime being evaluated. For example, replacing the Volumetric Ethanol Excise Tax Credit (VEETC) with the RFS, as occurred at the end 2011 when the VEETC was allowed to expire, would reduce emissions by 2.0 TgCO2e in 2015 for an expansion of ethanol of 11.4 billion liters. A policy regime consisting of the RFS alone would increase emissions by at least 4.5 TgCO2e for the same expansion of ethanol. Our findings highlight an important tension between land and fuel market leakage. Policy regimes that result in less land market leakage tend to lead to more domestic fuel market leakage per liter of ethanol added.
Substitution is used within attributional life cycle assessments (LCAs) as a means of avoiding allocation between co-products, and a number of existing standards and guidance documents permit its use in this way. This article discusses the appropriateness of substitution for attributional LCA, and suggests that the use of substitution introduces consequential elements into attributional analysis and that attributional assessments that use substitution will not be appropriate for consumption-based carbon accounting or corporate greenhouse gas reporting. This article suggests that, as a methodological principle, attributional LCA should only include actual physical burdens and should not include values for burdens that are avoided (i.e. do not physically occur). We also suggest that existing standards and guidance should be amended so that substitution is not permitted as a method within attributional LCA and that substitution should be clearly distinguished from expanding the function studied by an assessment. This article focuses on greenhouse gas LCA, but the discussion and conclusions apply to attributional LCA generally.
Belowground carbon (C) dynamics of terrestrial eco-systems play an important role in the global C cycle and thereby in climate regulation. Globally, land-use change is a major driver of changes in belowground C storage. The emerging bioenergy industry is likely to drive widespread land-use changes, including the replacement of annually tilled croplands with peren-nial bioenergy crops, and thereby to impact the climate system through alteration of belowground C dynam-ics. Mechanistic understanding of how land-use changes impact belowground C storage requires elucidation of changes in belowground C flows; how-ever, altered belowground C dynamics following land-use change have yet to be thoroughly quantified through field measurements. Here, we show that belowground C cycling pathways of establishing perennial bioenergy crops (0-to 3.5-year-old miscan-thus, switchgrass, and a native prairie mix) were sub-stantially altered relative to row crop agriculture (corn-soy rotation); specifically, there were substantial increases in belowground C allocation (>400%), belowground biomass (400–750%), root-associated respiration (up to 2,500%), moderate reductions in litter inputs (20–40%), and respiration in root-free soil (up to 50%). This more active root-associated C cycling of perennial vegetation provides a mechanism for ob-served net C sequestration by these perennial ecosys-tems, as well as commonly observed increases in soil C under perennial bioenergy crops throughout the world. The more active root-associated belowground C cycle of perennial vegetation implies a climate benefit of grassland maintenance or restoration, even if bio-mass is harvested annually for bioenergy production.
a b s t r a c t Products other than biofuels are produced in biofuel plants. For example, corn ethanol plants produce distillers' grains and solubles. Soybean crushing plants produce soy meal and soy oil, which is used for biodiesel production. Electricity is generated in sugarcane ethanol plants both for internal consumption and export to the electric grid. Future cellulosic ethanol plants could be designed to co-produce electricity with ethanol. It is important to take co-products into account in the life-cycle analysis of biofuels and several methods are available to do so. Although the International Standard Organization's ISO 14040 advocates the system boundary expansion method (also known as the ''displacement method'' or the ''substitution method'') for life-cycle analyses, application of the method has been limited because of the difficulty in identifying and quantifying potential products to be displaced by biofuel co-products. As a result, some LCA studies and policy-making processes have considered alternative methods. In this paper, we examine the available methods to deal with biofuel co-products, explore the strengths and weaknesses of each method, and present biofuel LCA results with different co-product methods within the U.S. context.
Globally, bioethanol is the largest volume biofuel used in the transportation sector, with corn-based ethanol production occurring mostly in the US and sugarcane-based ethanol production occurring mostly in Brazil. Advances in technology and the resulting improved productivity in corn and sugarcane farming and ethanol conversion, together with biofuel policies, have contributed to the significant expansion of ethanol production in the past 20 years. These improvements have increased the energy and greenhouse gas (GHG) benefits of using bioethanol as opposed to using petroleum gasoline. This article presents results from our most recently updated simulations of energy use and GHG emissions that result from using bioethanol made from several feedstocks. The results were generated with the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) model. In particular, based on a consistent and systematic model platform, we estimate life-cycle energy consumption and GHG emissions from using ethanol produced from five feedstocks: corn, sugarcane, corn stover, switchgrass and miscanthus.
We quantitatively address the impacts of a few critical factors that affect life-cycle GHG emissions from bioethanol. Even when the highly debated land use change GHG emissions are included, changing from corn to sugarcane and then to cellulosic biomass helps to significantly increase the reductions in energy use and GHG emissions from using bioethanol. Relative to petroleum gasoline, ethanol from corn, sugarcane, corn stover, switchgrass and miscanthus can reduce life-cycle GHG emissions by 19–48%, 40–62%, 90–103%, 77–97% and 101–115%, respectively. Similar trends have been found with regard to fossil energy benefits for the five bioethanol pathways.
This study reviews the current status, uncertainties and shortcomings of existing models of land use change (LUC) and associated greenhouse gas emissions as a result of biofuel production. The study also identifies options for improving the models and conducting further analysis. Moreover, because the extent of indirect LUC related to biofuels largely depends on other land uses – particularly agriculture - , this study explores strategies for mitigating overall LUC and its effects. Despite recent improvements and refinements of the models, this review finds large uncertainties, primarily related to the underlying data and assumptions of the market equilibrium models. There is thus still considerable scope for further scientific improvements of the modeling efforts. In addition, analyzing how overall LUC and its effects can be
minimized is an important topic for further research and can deliver more concrete input for developing proper policy strategies. Future studies should investigate the impact of sustainability criteria and the effects of strategies for mitigating LUC, such as increasing agricultural efficiency, optimizing bioenergy production chains, using currently unused
residues and by-products, and producing feedstocks on degraded and marginal land.
The indirect land use change (ILUC) effect of biofuels has called into question the greenhouse gas (GHG) mitigation benefit of biofuels compared with that of fossil fuels. This article reviews the various economic modeling approaches being used to assess the ILUC effect and discusses the key factors that influence estimates of its magnitude. We find that there is considerable variability in the magnitude of ILUC associated with a biofuel pathway across studies and within a study, depending on underlying model parameters. These estimates are sensitive to the scale of biofuel production, the mix of policies and biofuels considered, variations in the parametric assumptions that govern price transmission through international trade, and the ease of changes in land use at the intensive and extensive margins. We discuss the challenges in implementing policies to address ILUC.
The Intergovernmental Panel on Climate Change's Special Report on Renewable Energy Sources and Climate Change Mitigation (SRREN) assesses the role of bioenergy as a solution to meeting energy demand in a climate-constrained world. Based on integrated assessment models, the SRREN states that deployed bioenergy will contribute the greatest proportion of primary energy among renewable energies and result in greenhouse-gas emission reductions. The report also acknowledges insights from life-cycle assessments, which characterize biofuels as a potential source of significant greenhouse-gas emissions and environmental harm. The SRREN made considerable progress in bringing together contrasting views on indirect land-use change from inductive bottom-up studies, such as life-cycle analysis, and deductive top-down assessments. However, a reconciliation of these contrasting views is still missing. Tackling this challenge is a fundamental prerequisite for future bioenergy assessment.
Car ownership is set to triple by 2050, trucking activity will double and air travel could increase fourfold. This book examines how to enable mobility without accelerating climate change. It finds that if we change the way we travel, adopt technologies to improve vehicle efficiency and shift to low-CO2 fuels, we can move onto a different pathway where transport CO2 emissions by 2050 are far below current levels, at costs that are lower than many assume.
The report discusses the prospects for shifting more travel to the most efficient modes and reducing travel growth rates, improving vehicle fuel efficiency by up to 50% using cost-effective, incremental technologies, and moving toward electricity, hydrogen, and advanced biofuels to achieve a more secure and sustainable transport future. If governments implement strong policies to achieve this scenario, transport can play its role and dramatically reduce CO2 emissions by 2050.
In Power and Society, Harold D. Lasswell collaborates with a brilliant young philosopher, Abraham Kaplan, to formulate basic theoretical concepts and hypotheses of political science, providing a framework for further inquiry into the political process. This is a classic book of political theory written by two of the most influential social scientists of the twentieth century.The authors find their subject matter in interpersonal relations, not abstract institutions or organizations, and their analysis of power is related to human values. They argue that revolution is a part of the political process, and ideology has a role in political affairs. The importance of class, both as social fact and social symbol, is reflected in their detailed analysis, and emphasis on merit rather than rank, skill rather than status, as keystones of democratic rule.The authors note that power is only one of the values and instruments manifested in interpersonal relations; it cannot be understood in abstraction from other values. Lasswell and Kaplan call for the replacement of “power politics,” both in theory and in practice, by a conception in which attention is focused on the human consequences of power as the major concern of both political thought and political action. The basic discussions of core concepts in political science make Power and Society of continuing importance to scholars, government officials, and politicians.
Life-cycle assessment (LCA) is a new method for exploring the environmental implications of human action. Like all methods, it is analytically limited and consequently it must be used with caution. Recent papers have criticized LCA and caution against its use in all but a few narrow applications. Even while accepting many of these arguments, this article argues that LCAs, like other analytic frameworks used in the policy and planning domains, have important uses in shaping the processes by which both products and policies are designed.The arguments made against the use of LCAs omit comparisons to realistic appraisals of alternative and competing methods of environmental assessment.
This chapter presents background on greenhouse gas emission (GHG) formation from motor vehicles and then estimates of GHG emissions from various types of electric vehicles (EVs) such as battery, fuel cell, and plug-in hybrid electric vehicles from studies conducted by research groups at universities, national labs, government agencies, and other groups are reviewed. EVs can even have very low to zero emissions of GHGs when they run on renewable fuels; however, at present, EVs are more expensive than other options that offer significant reductions at lower costs as electricity is largely generated from conventional fuels. When coal is heavily used to produce electricity or H2, GHG emissions tend to increase significantly compared with conventional fuel alternatives. Without carbon capture and sequestration, coal-based fuels even in conjunction with electric drive systems offer little or no benefit. Much deeper reductions of over 90% in GHG are possible for battery electric vehicles (BEVs) if they are run on renewable or nuclear power sources. Plug-in hybrid electric vehicles (PHEVs) running on gasoline can reduce emissions by 20–60%, and fuel cell EVs can reduce GHGs by 30–50% when they run on natural gas-derived H2 and up to 95% or more when the H2 is produced and potentially compressed by using renewable feedstocks.
Recently, there has been an explosion of life-cycle assessment (LCA) studies of biofuels to support biofuel policy making. It is difficult to draw general conclusions from the set of studies due to the variation in outcomes. Causes of this variation include real-world differences, data uncertainties and methodological choices. In this review we explore some of the more complicated sources of differences in findings related to LCA methodology by reviewing 67 LCA studies published between 2005 and 2010. A very important and particularly difficult problem to solve is coproduct allocation. Different allocation methods, all approved under the International Organization for Standardization (ISO) standard for LCA studies, can cause improvement percentages compared with fossil fuels to vary from negative to above 100%. The treatment of biogenic carbon is another important issue. Most studies include neither extractions nor emissions of biogenic CO2, but a number of these LCAs do include both, leading to very different conclusions on greenhouse gas performance of biofuel chains.
This study shows how the assessment of emissions reductions from CO2 capture is critically dependent on the choice of multi-gas equivalency metric and climate impact time horizon. This has implications for time-sensitive mitigation policies, in particular when considering relative impact of short-lifetime gases. CO2, CH4 and N2O emissions from a coal-fired power plant in Brazil are used to estimate and compare the CO2-equivalent emissions based on standard practice global warming potentials GWP-100 with the less common GWP-50 and variable GWP for impact target years 2050 and 2100. Emission reductions appear lower for the variable metric, when the choice of target year is critical: 73% in 2100 and 60% in 2050. Reductions appear more favorable using a metric with a fixed time horizon, where the choice of time horizon is important: 77% for GWP-100 and 71% for GWP-50. Since CH4 emissions from mining have a larger contribution in the total emission of a plant with capture compared to one without, different perspectives on the impact of CH4 are analyzed. Use of variable GWP implies that CH4 emissions appear 39% greater in 2100 than with use of fixed GWP and 91% greater in 2050.
Evaluation of indirect land-use changes due to biofuels has been very controversial over the past few years, as doubts have arisen about the environmental benefits of growing crops for use as a substitute for fossil fuels. This paper presents an overview of the MIRAGE-BioF CGE modeling approach to biofuel policies assessment. Our framework introduces new innovative features that strengthen the relevance of the methodology. In particular, a more detailed and consistent database has been developed to represent the sectors and substitution mechanisms at play. Moreover, the model used has been improved in several important ways to better reproduce the agricultural supply function and land-use change. However, we also emphasize the critical uncertainties that prevent us from being able to provide a precise two-digit figure on the extent of land-use change and associated emissions. We illustrate these efforts with the case of EU biofuel mandates implications. We show that emissions from the current national targets in the EU could lead to an indirect effect of land-use expansion ranging from 1 ha per TJ consumed to 12 ha per TJ with a median value of 3.4 ha per TJ. The associated emissions in a 20-year period would range from 10 gCO2/MJ to 115 gCO2/MJ, with a median value of 38 gCO2/MJ. These results seriously question the sustainability of the current EU biofuels policy and emphasize the even more dramatic effect of a biodiesel-oriented EU biofuel program, which was found to emit two times more than an EU ethanol-oriented program.
Summary This article evaluates the implications of uncertainty in the life cycle (LC) energy efficiency and greenhouse gas (GHG) emissions of rapeseed oil (RO) as an energy carrier displacing fossil diesel (FD). Uncertainties addressed include parameter uncertainty as well as scenario uncertainty concerning how RO coproduct credits are accounted for (uncertainty due to modeling choices). We have carried out an extensive data collection to build an LC inventory accounting for parameter uncertainty. Different approaches for carbon stock changes associated with converting set-aside land to rapeseed cultivation have been considered, which result in different values: from −0.25 t C/ha.yr (carbon uptake by the soil in tonnes per hectare year) to 0.60 t C/ha.yr (carbon emission). Energy renewability efficiency and GHG emissions of RO are presented, which show the influence of parameter versus scenario uncertainty. Primary energy savings and avoided GHG emissions when RO displaces FD have also been calculated: Avoided GHG emissions show considerably higher uncertainty than energy savings, mainly due to land use (nitrous oxide emissions from soil) and land use conversion (carbon stock changes). Results demonstrate the relevance of applying uncertainty approaches; emphasize the need to reduce uncertainty in the environmental life cycle modeling, particularly GHG emissions calculation; and show the importance of integrating uncertainty into the interpretation of results.
The European Commission has a mandate from the EU's Renewable Energy and Fuel Quality Directives to propose a methodology, consistent with the best available science, to address indirect land use change (iLUC). One proposed solution to the iLUC problem is the application of iLUC factors in European fuels policy – it is widely expected that should the EU adopt such iLUC factors, they would be based on iLUC modelling using the International Food Policy Research Institute's (IFPRI) MIRAGE model. Taking the iLUC factors from IFPRI MIRAGE as our central estimate, we use Monte Carlo analysis on a simple model of potential biofuel pathways for Europe to assess the likely average carbon saving from three possible European biofuel policy scenarios: no action on iLUC; raised GHG thresholds for direct emissions savings; and the introduction of iLUC factors. We find that without iLUC factors (or some other effective iLUC minimization approach) European biofuel mandates are unlikely to deliver significant GHG emissions benefits in 2020, and have a substantial probability of increasing net GHG emissions. In contrast, the implementation of iLUC factors is likely to significantly increase the carbon savings from EU biofuel policy. With iLUC factors, it is likely that most permitted pathways would conform to the Renewable Energy Directive requirement for a minimum 50% GHG reduction compared to fossil fuels.
Worldwide land is a limited resource and its use for the production of biofuels and other agricultural products can impact greenhouse gas emissions (GHG). Several models and approaches have been used to assess the direct (dLUC) and indirect land use change (iLUC) carbon intensity – i.e. the amount of CO2 emitted per unit of biofuel produced – of biofuels, but their outcomes diverge significantly. This analysis of 15 studies published between 2008 and 2010 (i) summarized and compared models and approaches used to estimate the dLUC and iLUC carbon intensities of biofuels, and (ii) assessed the mechanisms that led to the variation in the outcomes. The data show that the dLUC carbon intensity ranged from −52 to 34 g CO2 MJ−1, whereas the iLUC ranged from 0 to 327 g CO2 MJ−1 for bioethanol depending on the feedstock, on the type of land used or displaced and on the amortization period. The total LUC carbon intensity of bioethanol was found to be −29% to 384% of that of gasoline. This means that in some cases, LUC could potentially alter the GHG benefits of biofuels. Standardizing assumptions, carbon stock changes and methodologies for estimating the dLUC and iLUC carbon intensity will ensure more consistency and meaningful comparisons across studies in the future. This might then enable policy makers to make better justified judgments on the sustainability of biofuels.
The role of biomass as a primary energy resource is highly debated. Next generation biofuels are suggested to be associated with low specific greenhouse gas emissions. But land consumption, demand for scarce water, competition with food production and harmful indirect land-use effects put a question mark over the beneficial effects of bioenergy deployment. In this paper, we investigate the current state of bioenergy assessments and scrutinize the topics and perspectives explored in the Special Report on Renewable Energy Sources and Climate Change. We suggest that an appropriate assessment requires a comprehensive literature review, the explicit exposition of disparate viewpoints, and exploration of policy-relevant content based on plausible "storylines". We illustrate these storylines with the IPCC's emission scenarios and point out routes to improve assessment making on the future role of bioenergy.
A fundamental, generally implicit, assumption of the Intergovernmental
Panel on Climate Change reports and many energy analysts is that each
unit of energy supplied by non-fossil-fuel sources takes the place of a
unit of energy supplied by fossil-fuel sources. However, owing to the
complexity of economic systems and human behaviour, it is often the case
that changes aimed at reducing one type of resource consumption, either
through improvements in efficiency of use or by developing substitutes,
do not lead to the intended outcome when net effects are considered.
Here, I show that the average pattern across most nations of the world
over the past fifty years is one where each unit of total national
energy use from non-fossil-fuel sources displaced less than one-quarter
of a unit of fossil-fuel energy use and, focusing specifically on
electricity, each unit of electricity generated by non-fossil-fuel
sources displaced less than one-tenth of a unit of fossil-fuel-generated
electricity. These results challenge conventional thinking in that they
indicate that suppressing the use of fossil fuel will require changes
other than simply technical ones such as expanding non-fossil-fuel
energy production.
The design of multi-gas mitigation policies requires methods for comparing the climate impact of different forcing agents—so-called metrics. A multitude of climate metrics has been presented in the literature. Key characteristics of any metric are (a) its impact function, i.e. its functional relationship to physical climate parameters, and (b) the weighting of impacts over time. In view of these characteristics, we present a physico-economic framework which allows classifying climate metrics from the literature in a straight-forward manner. From the economics perspective, the Global Damage Potential can be considered as a first-best benchmark metric since it ensures that the trade-off between different forcing agents is efficient. The conceptual framework based on economic principles shows that virtually all climate metrics including Global Warming Potential and Global Cost Potential can be constructed as variants of the Global Damage Potential. The framework facilitates a structured discussion on climate metrics since it reveals normative assumptions and simplifications that are implicit to the choice of a climate metric. The evaluation of commonly used metric approaches in terms of uncertainties reveals that the choice of metric is largely characterized by trade-offs between different kinds of uncertainties: explicit ones which are directly linked to operational feasibility and implicit structural ones which reflect the degree of policy relevance. Based on our findings, we suggest as an alternative option for policy applications to base exchange rates between forcing agents on an explicit analysis of the value-based, scientific and scenario uncertainties in the context of a physico-economic metric, rather than eliminating the relevant uncertainties by the choice of a physical metric.
Sugarcane produced in Brazil has several environmental advantages. However, burning residues, which leads to GHG and black carbon (BC) emissions, has been used to facilitate manual harvest. BC emissions have a net warming effect and cause health problems. Mechanized harvest without burning is gradually replacing manually harvested burned sugarcane. Global warming potential (GWP) and human health indicators of sugarcane ethanol production in Brazil, in the pre-mechanization (100% burned), current (∼50% burned) and future (100% without burning) scenarios, were calculated. In the past, the GWP of ethanol production was 1.1 kg CO2 eq L−1 and BC emissions were 32.6 kg CO2 eq L−1. The human health impact in disability adjusted life years (DALY) was 3.16E−05 DALY L−1 ethanol. The current ethanol production process has a GWP 46% smaller, while BC emissions are seven times smaller than before mechanization started. The human health impact is currently 7.72E−06 DALY L−1. In the future, with complete mechanization and the integration of first and second generation ethanol, the expected GWP emissions will be 70% smaller, and BC emissions will be 216 times smaller than when all sugarcane was harvested with burning. These results show that ethanol production in Brazil is improving in terms of global warming and human health aspects. Other upstream aspects of ethanol production such as direct and indirect land use change, and downstream impacts such as the emissions of acetaldehydes were not considered in this study, which focused on a major technological shift in residue management in the agricultural phase of sugarcane ethanol production. A broader assessment of the sustainability of ethanol must account for those issues, as well as economic and social aspects. Sugarcane-derived ethanol produced in Brazil has been considered one of the most sustainable biofuels options, but it is essential to identify and promote practices and policies that further improve its production, such as the phase out of pre-harvest sugarcane burning and the increase in ethanol yield per unit of area.
Policies formulated to reduce greenhouse gas (GHG) emissions, such as a low-carbon fuel standard, frequently rely on life-cycle assessment (LCA) to estimate emissions, but LCA results are often highly uncertain. This study develops life-cycle models that quantitatively and qualitatively describe the uncertainty and variability in GHG emissions for both fossil fuels and ethanol and examines mechanisms to reduce those uncertainties in the policy process. Uncertainty regarding emissions from gasoline is non-negligible, with an estimated 90% confidence interval ranging from 84 to 100 g CO2e/MJ. Emissions from biofuels have greater uncertainty. The widths of the 90% confidence intervals for corn and switchgrass ethanol are estimated to be on the order of 100 g CO2e/MJ, and removing emissions from indirect land use change still leaves significant remaining uncertainty. Though an opt-in policy mechanism can reduce some uncertainty by incentivizing producers to self-report fuel production parameters, some important parameters, such as land use change emissions and nitrogen volatilization, cannot be accurately measured and self-reported. Low-carbon fuel policies should explicitly acknowledge, quantify, and incorporate uncertainty in life cycle emissions in order to more effectively achieve emissions reductions. Two complementary ways to incorporate this uncertainty in low carbon fuel policy design are presented.
Life cycle assessment (LCA) can be an invaluable tool for the structured environmental impact assessment of bioenergy product systems. However, the methodology's static temporal and spatial scope combined with its restriction to emission-based metrics in life cycle impact assessment (LCIA) inhibits its effectiveness at assessing climate change impacts that stem from dynamic land surface–atmosphere interactions inherent to all biomass-based product systems. In this paper, we focus on two dynamic issues related to anthropogenic land use that can significantly influence the climate impacts of bioenergy systems: i) temporary changes to the terrestrial carbon cycle; and ii) temporary changes in land surface albedo—and illustrate how they can be integrated within the LCA framework.In the context of active land use management for bioenergy, we discuss these dynamics and their relevancy and outline the methodological steps that would be required to derive case-specific biogenic CO2 and albedo change characterization factors for inclusion in LCIA. We demonstrate our concepts and metrics with application to a case study of transportation biofuel sourced from managed boreal forest biomass in northern Europe. We derive GWP indices for three land management cases of varying site productivities to illustrate the importance and need to consider case- or region-specific characterization factors for bioenergy product systems. Uncertainties and limitations of the proposed metrics are discussed.
Purpose Biological sequestration can increase the carbon stocks of non-atmospheric reservoirs (e.g. land and land-based products). Since this contained carbon is sequestered from, and retained outside, the atmosphere for a period of time, the concentration of CO 2 in the atmosphere is temporar-ily reduced and some radiative forcing is avoided. Carbon removal from the atmosphere and storage in the biosphere or anthroposphere, therefore, has the potential to mitigate climate change, even if the carbon storage and associated benefits might be temporary. Life cycle assessment (LCA) and carbon footprinting (CF) are increasingly popular tools for the envi-ronmental assessment of products, that take into account their entire life cycle. There have been significant efforts to develop robust methods to account for the benefits, if any, of seques-tration and temporary storage and release of biogenic carbon. However, there is still no overall consensus on the most appropriate ways of considering and quantifying it. Method This paper reviews and discusses six available methods for accounting for the potential climate impacts of carbon sequestration and temporary storage or release of biogenic carbon in LCA and CF. Several viewpoints and approaches are presented in a structured manner to help decision-makers in their selection of an option from com-peting approaches for dealing with timing issues, including delayed emissions of fossil carbon. Results Key issues identified are that the benefits of tempo-rary carbon removals depend on the time horizon adopted when assessing climate change impacts and are therefore not purely science-based but include value judgments. We therefore did not recommend a preferred option out of the six alternatives presented here. Conclusions Further work is needed to combine aspects of scientific and socio-economic understanding with value judgements and ethical considerations.
Carbon dioxide capture and storage (CCS) is increasingly seen as a way for society to enjoy the benefits of fossil fuel energy sources while avoiding the climate disruption associated with fossil CO2 emissions. A decision to deploy CCS technology at scale should be based on robust information on its overall costs and benefits. Life-cycle assessment (LCA) is a framework for holistic assessment of the energy and environmental footprint of a system, and can provide crucial information to policy-makers, scientists, and engineers as they develop and deploy CCS systems. We identify seven key issues that should be considered to ensure that conclusions and recommendations from CCS LCA are robust: energy penalty, functional units, scale-up challenges, non-climate environmental impacts, uncertainty management, policy-making needs, and market effects. A number of life-cycle studies have focused on detailed assessments of individual CCS technologies and applications. While such studies provide important data and information on technology performance, such case-specific data are inadequate to fully inform the decision making process. LCA should aim to describe the system-wide environmental implications of CCS deployment at scale, rather than a narrow analysis of technological performance of individual power plants.
In this article an overview is given of present applications of life cycle assessment (LCA) as an instrument for the support of decision-making. Attention is given to original expectations, present drawbacks and future perspectives. The following dimensions are chosen for this overview: the main users, with a distinction between governments, companies and non-governmental organizations; the level of sophistication, distinguishing between LCA as a concept, qualitative LCA and quantitative LCA, with varying degrees of detail within the latter; a distinction between applications at an operational and at a strategic level; a distinction between internal and external applications; and finally the level of completeness of the study, i.e. which limitations are set a priori for a study. Three types of drawbacks are encountered: purely technical problems, methodological problems and communication problems. Possible ways to cope with these are discussed.
Background, aims, and scope
Life cycle assessment (LCA) stands as the pre-eminent tool for estimating environmental effects caused by products and processes from ‘cradle to grave’ or ‘cradle to cradle.’ It exists in multiple forms, claims a growing list of practitioners and remains a focus of continuing research. Despite its popularity and codification by organizations such as the International Organization for Standardization and the Society of Environmental Toxicology and Chemistry, life cycle assessment is a tool in need of improvement. Multiple authors have written about its individual problems, but a unified treatment of the subject is lacking. The following literature survey gathers and explains issues, problems and problematic decisions currently limiting LCA’s impact assessment and interpretation phases.
Main features
The review identifies 15 major problem areas and organizes them by the LCA phases in which each appears. This part of the review focuses on the latter eight problems. It is meant as a concise summary for practitioners interested in methodological limitations which might degrade the accuracy of their assessments. For new researchers, it provides an overview of pertinent problem areas toward which they might wish to direct their research efforts. Having identified and discussed LCA’s major problems, closing sections highlight the most critical problems and briefly propose research agendas meant to improve them.
Results and discussion
Multiple problems occur in each of LCA’s four phases and reduce the accuracy of this tool. Considering problem severity and the adequacy of current solutions, six of the 15 discussed problems are of paramount importance. In LCA’s latter two phases, spatial variation and local environmental uniqueness are critical problems requiring particular attention. Data availability and quality are identified as critical problems affecting all four phases.
Conclusions and recommendations
Observing that significant efforts by multiple researchers have not resulted in a single, agreed upon approach for the first three critical problems, development of LCA archetypes for functional unit definition, boundary selection and allocation is proposed. Further development of spatially explicit, dynamic modeling is recommended to ameliorate the problems of spatial variation and local environmental uniqueness. Finally, this paper echoes calls for peer-reviewed, standardized LCA inventory and impact databases, and it suggests the development of model bases. Both of these efforts would help alleviate persistent problems with data availability and quality.
Background, aims, and scope: Life cycle assessment (LCA) stands as the pre-eminent tool for estimating environmental effects caused by products and processes from 'cradle to grave' or 'cradle to cradle.' It exists in multiple forms, claims a growing list of practitioners, and remains a focus of continuing research. Despite its popularity and codification by organizations such as the International Organization for Standards and the Society of Environmental Toxicology and Chemistry, life cycle assessment is a tool in need of improvement. Multiple authors have written about its individual problems, but a unified treatment of the subject is lacking. The following literature survey gathers and explains issues, problems and problematic decisions currently limiting LCA's goal and scope definition and life cycle inventory phases. Main features: The review identifies 15 major problem areas and organizes them by the LCA phases in which each appears. This part of the review focuses on the first 7 of these problems occurring during the goal and scope definition and life cycle inventory phases. It is meant as a concise summary for practitioners interested in methodological limitations which might degrade the accuracy of their assessments. For new researchers, it provides an overview of pertinent problem areas toward which they might wish to direct their research efforts. Results and discussion: Multiple problems occur in each of LCA's four phases and reduce the accuracy of this tool. Considering problem severity and the adequacy of current solutions, six of the 15 discussed problems are of paramount importance. In LCA's first two phases, functional unit definition, boundary selection, and allocation are critical problems requiring particular attention. Conclusions and recommendations: Problems encountered during goal and scope definition arise from decisions about inclusion and exclusion while those in inventory analysis involve flows and transformations. Foundational decisions about the basis of comparison (functional unit), bounds of the study, and physical relationships between included processes largely dictate the representativeness and, therefore, the value of an LCA. It is for this reason that problems in functional unit definition, boundary selection, and allocation are the most critical examined in the first part of this review.
Despite the ever-growing body of life cycle assessment (LCA) literature on electricity generation technologies, inconsistent methods and assumptions hamper comparison across studies and pooling of published results. Synthesis of the body of previous research is necessary to generate robust results to assess and compare environmental performance of different energy technologies for the benefit of policy makers, managers, investors, and citizens. With funding from the U.S. Department of Energy, the National Renewable Energy Laboratory initiated the LCA Harmonization Project in an effort to rigorously leverage the numerous individual studies to develop collective insights. The goals of this project were to: (1) understand the range of published results of LCAs of electricity generation technologies, (2) reduce the variability in published results that stem from inconsistent methods and assumptions, and (3) clarify the central tendency of published estimates to make the collective results of LCAs available to decision makers in the near term. The LCA Harmonization Project's initial focus was evaluating life cycle greenhouse gas (GHG) emissions from electricity generation technologies. Six articles from this first phase of the project are presented in a special supplemental issue of the Journal of Industrial Ecology on Meta-Analysis of LCA: coal (Whitaker et al. 2012), concentrating solar power (Burkhardt et al. 2012), crystalline silicon photovoltaics (PVs) (Hsu et al. 2012), thin-film PVs (Kim et al. 2012), nuclear (Warner and Heath 2012), and wind (Dolan and Heath 2012). Harmonization is a meta-analytical approach that addresses inconsistency in methods and assumptions of previously published life cycle impact estimates. It has been applied in a rigorous manner to estimates of life cycle GHG emissions from many categories of electricity generation technologies in articles that appear in this special supplemental supplemental issue, reducing the variability and clarifying the central tendency of those estimates in ways useful for decision makers and analysts. Each article took a slightly different approach, demonstrating the flexibility of the harmonization approach. Each article also discusses limitations of the current research, and the state of knowledge and of harmonization, pointing toward a path of extending and improving the meta-analysis of LCAs.
The body of life cycle assessment (LCA) literature is vast and has grown over the last decade at a dauntingly rapid rate. Many LCAs have been published on the same or very similar technologies or products, in some cases leading to hundreds of publications. One result is the impression among decision makers that LCAs are inconclusive, owing to perceived and real variability in published estimates of life cycle impacts. Despite the extensive available literature and policy need formore conclusive assessments, only modest attempts have been made to synthesize previous research. A significant challenge to doing so are differences in characteristics of the considered technologies and inconsistencies in methodological choices (e.g., system boundaries, coproduct allocation, and impact assessment methods) among the studies that hamper easy comparisons and related decision support. An emerging trend is meta-analysis of a set of results from LCAs, which has the potential to clarify the impacts of a particular technology, process, product, or material and produce more robust and policy-relevant results. Meta-analysis in this context is defined here as an analysis of a set of published LCA results to estimate a single or multiple impacts for a single technology or a technology category, either in a statistical sense (e.g., following the practice in the biomedical sciences) or by quantitative adjustment of the underlying studies to make them more methodologically consistent. One example of the latter approach was published in Science by Farrell and colleagues (2006) clarifying the net energy and greenhouse gas (GHG) emissions of ethanol, in which adjustments included the addition of coproduct credit, the addition and subtraction of processes within the system boundary, and a reconciliation of differences in the definition of net energy metrics. Such adjustments therefore provide an even playing field on which all studies can be considered and at the same time specify the conditions of the playing field itself. Understanding the conditions under which a meta-analysis was conducted is important for proper interpretation of both the magnitude and variability in results. This special supplemental issue of the Journal of Industrial Ecology includes 12 high-quality metaanalyses and critical reviews of LCAs that advance understanding of the life cycle environmental impacts of different technologies, processes, products, and materials. Also published are three contributions on methodology and related discussions of the role of meta-analysis in LCA. The goal of this special supplemental issue is to contribute to the state of the science in LCA beyond the core practice of producing independent studies on specific products or technologies by highlighting the ability of meta-analysis of LCAs to advance understanding in areas of extensive existing literature. The inspiration for the issue came from a series of meta-analyses of life cycle GHG emissions from electricity generation technologies based on research from the LCA Harmonization Project of the National Renewable Energy Laboratory (NREL), a laboratory of the U.S. Department of Energy, which also provided financial support for this special supplemental issue. (See the editorial from this special supplemental issue [Lifset 2012], which introduces this supplemental issue and discusses the origins, funding, peer review, and other aspects.) The first article on reporting considerations for meta-analyses/critical reviews for LCA is from Heath and Mann (2012), who describe the methods used and experience gained in NREL's LCA Harmonization Project, which produced six of the studies in this special supplemental issue. Their harmonization approach adapts key features of systematic review to identify and screen published LCAs followed by a meta-analytical procedure to adjust published estimates to ones based on a consistent set of methods and assumptions to allow interstudy comparisons and conclusions to be made. In a second study on methods, Zumsteg and colleagues (2012) propose a checklist for a standardized technique to assist in conducting and reporting systematic reviews of LCAs, including meta-analysis, that is based on a framework used in evidence-based medicine. Widespread use of such a checklist would facilitate planning successful reviews, improve the ability to identify systematic reviews in literature searches, ease the ability to update content in future reviews, and allow more transparency of methods to ease peer review and more appropriately generalize findings. Finally, Zamagni and colleagues (2012) propose an approach, inspired by a meta-analysis, for categorizing main methodological topics, reconciling diverging methodological developments, and identifying future research directions in LCA. Their procedure involves the carrying out of a literature review on articles selected according to predefined criteria.
With increasing use of biomass for energy, questions arise about the validity of bioenergy as a means to reduce greenhouse gas emissions and dependence on fossil fuels. Life Cycle Assessment (LCA) is a methodology able to reveal these environmental and energy performances, but results may differ even for apparently similar bioenergy systems. Differences are due to several reasons: type and management of raw materials, conversion technologies, end-use technologies, system boundaries and reference energy system with which the bioenergy chain is compared. Based on review of published papers and elaboration of software data concerning greenhouse gas and energy balances of bioenergy, other renewable and conventional fossil systems, this paper discusses key issues in bioenergy system LCA. These issues have a strong influence on the final results but are often overlooked or mishandled in most of the studies available in literature. The article addresses the following aspects: recognition of the biomass carbon cycle, including carbon stock changes in biomass and soil over time; inclusion of nitrous oxide and methane emissions from agricultural activities; selection of the appropriate fossil reference system; homogeneity of the input parameters in Life Cycle Inventories; influence of the allocation procedure when multiple products are involved; future trends in bioenergy (i.e. second-generation biofuels and biorefineries).
Increasing energy efficiency brings emissions savings. Claims that it backfires are a distraction, say Kenneth Gillingham and colleagues.
This article challenges the notion that energy efficiency and ‘clean’ energy technologies can deliver sufficient degrees of climate change mitigation. By six arguments not widely recognized in the climate policy arena, we argue that unrealistic technology optimism exists in current climate change mitigation assessments, and, consequently, world energy and climate policy. The overarching theme of the arguments is that incomplete knowledge of indirect effects, and neglect of interactions between parts of physical and social sub-systems, systematically leads to overly optimistic assessments. Society must likely seek deeper changes in social and economic structures to preserve the climatic conditions to which the human civilization is adapted. We call for priority to be given to research evaluating aspects of mitigation in a broad, system-wide perspective.
Purpose
Consequential LCA (CLCA) is becoming widely used in the scientific community as a modelling technique which describes the consequences of a decision. However, despite the increasing number of case studies published, a proper systematization of the approach has not yet been achieved. This paper investigates the methodological implications of CLCA and the extent to which the applications are in line with the theoretical dictates. Moreover, the predictive and explorative nature of CLCA is discussed, highlighting the role of scenario modelling in further structuring the methodology.
Methods
An extensive literature review was performed, involving around 60 articles published over a period of approximately 18 years, and addressing both methodological issues and applications. The information was elaborated according to two main aspects: what for (questions and modes of LCA) and what (methodological implications of CLCA), with focus on the nature of modelling and on the identification of the affected processes.
Results and discussion
The analysis points out that since the modelling principles of attributional LCA (ALCA) and CLCA are the same, what distinguishes the two modes of LCA is the choice of the processes to be included in the system (i.e. in CLCA, those that are affected by the market dynamics). However, the identification of those processes is often done inconsistently, using different arguments, which leads to different results. We suggest the use of scenario modelling as a way to support CLCA in providing a scientifically sound basis to model specific product-related futures with respect to technology development, market shift, and other variables.
Conclusions
The CLCA is a sophisticated modelling technique that provides a way to assess the environmental consequences of an action/decision by including market mechanisms into the analysis. There is still room for improvements of the method and for further research, especially in relation to the following aspects: clarifying when and which market information is important and necessary; understanding the role of scenario modelling within CLCA; and developing a procedure to support the framing of questions to better link questions to models. Moreover, we suggest that the logic of mechanisms could be the reading guide for overcoming the dispute between ALCA and CLCA. Going further, this logic could also be extended, considering CLCA as an approach—rather than as a modelling principle with defined rules—to deepen LCA, providing the conceptual basis for including more mechanisms than just the market ones.