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Life Cycle Assessment of Greenhouse Gas Emissions

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The construction sector is a key actor for achieving the sustainable development goals, particularly from an environmental point of view, due to the significant sector's contribution to energy consumption, greenhouse gas and pollutants emissions, waste generation, resources depletion etc. Life Cycle Assessment (LCA) is a multi-criteria tool to assess environmental impacts, preventing the impact transferring from one life cycle stage to another and thus is widely used to support decision-making. Consequential LCA (CLCA) can be particularly relevant for decisions involving non-marginal changes and may have an important role in supporting decision-makers of the construction sector by giving a wider comprehension of the environmental impacts associated with the changes caused by their decisions. Particularly when assessing large-scale consequences, it is recommended to couple an economic model to the CLCA methodology to assess the changes in the background system. Therefore, this research aims at reviewing the CLCA works applied to the construction sector and the use of economic models in CLCA for assessing non-marginal changes. For that, the review is divided in two parts: the first reviews the CLCA works and papers in the construction sector; and the second part reviews CLCA studies that assess non-marginal changes, regardless the activity or sector.
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This paper presents an original life cycle assessment (LCA) of a concentrating solar power (CSP) plant with thermochemical energy storage (TCES). The studied CSP plant is a hypothetic solar tower plant with a Rankine power cycle, and the TCES material used is calcium hydroxide. Based on three proposed TCES integration concepts, detailed sizing and the associated emission inventory are performed for four main groups that constitute the CSP plant, including the solar field, the solar tower, the storage system and the power cycle. Various midpoint impact categories are evaluated using the IMPACT 2002+ method embedded in the SimaPro 7.3 software. A sensitivity analysis is performed to identify the most influencing elements of the CSP plant on the environmental impacts. LCA results show that the CSP plant with different TCES integration alternatives has comparable global warming potential (approximately 11 kg CO2.eq/MWh) and energy payback time (approximately 4 months). The additional environmental burden due to the addition of the TCES system is relatively small (about 30%). The use of calcium hydroxide for the TCES has noticeable midpoint impacts on the respiratory inorganics, the terrestrial ecotoxicity and the mineral extraction. Solar field group (heliostat mirrors) is generally the most sensitive and environmental impacting factor of the CSP installation. The Turbine integration concept has the smallest environmental impacts among the three concepts proposed.
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Introduction The Monte Carlo technique is widely used and recommended for including uncertainties LCA. Typically, 1000 or 10,000 runs are done, but a clear argument for that number is not available, and with the growing size of LCA databases, an excessively high number of runs may be a time-consuming thing. We therefore investigate if a large number of runs are useful, or if it might be unnecessary or even harmful. Probability theory We review the standard theory or probability distributions for describing stochastic variables, including the combination of different stochastic variables into a calculation. We also review the standard theory of inferential statistics for estimating a probability distribution, given a sample of values. For estimating the distribution of a function of probability distributions, two major techniques are available, analytical, applying probability theory and numerical, using Monte Carlo simulation. Because the analytical technique is often unavailable, the obvious way-out is Monte Carlo. However, we demonstrate and illustrate that it leads to overly precise conclusions on the values of estimated parameters, and to incorrect hypothesis tests. Numerical illustration We demonstrate the effect for two simple cases: one system in a stand-alone analysis and a comparative analysis of two alternative systems. Both cases illustrate that statistical hypotheses that should not be rejected in fact are rejected in a highly convincing way, thus pointing out a fundamental flaw. Discussion and conclusions Apart form the obvious recommendation to use larger samples for estimating input distributions, we suggest to restrict the number of Monte Carlo runs to a number not greater than the sample sizes used for the input parameters. As a final note, when the input parameters are not estimated using samples, but through a procedure, such as the popular pedigree approach, the Monte Carlo approach should not be used at all.
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Purpose Life cycle assessment (LCA) is intended as a quantitative decision support tool. However, the large amount of uncertainty characteristic of LCA studies reduces confidence in results. To date, little research has been reported regarding the comparative sources of uncertainty (and their relative importance) and how, or how commonly, they are quantified in attributional and consequential LCA. This paper answers these questions based on a review of recent LCA studies and methods papers, and advances recommendations for improved practice. Methods All relevant LCA methods papers as well as case studies (amounting to 2687 journal articles) published from 2014 to 2018 in the top seven journals publishing LCA studies were reviewed. Common sources and methods for analysis of uncertainty in both attributional and consequential LCA were described, and their frequency of application evaluated. Observed practices were compared to best practice recommendations from methods papers, and additional recommendations were advanced. Results and discussion Less than 20% of LCA studies published in the past five years reported any kind of uncertainty analysis. There are many different sources of uncertainty in LCA, which can be classified as parameter, scenario or model uncertainty. Parameter uncertainty is most often reported, although the other types are considered equally important. There are also sources of uncertainty specific to each kind of LCA—in particular related to the resolution of multi-functionality problems (i.e. allocation in attributional LCA versus the definition of market-mediated substitution scenarios in consequential LCA). However, there are currently no widely applied methods to specifically account for these sources of uncertainty other than sensitivity analysis. Monte Carlo sampling was the most popular method used for propagating uncertainty results, regardless of LCA type. Conclusions Data quality scores and inherent (i.e. stochastic) uncertainty data are widely available in LCI databases, and researchers should generally be able to define comparable uncertainty information for their primary data. Moreover, uncertainty propagation for parameter uncertainty is supported by LCA modelling software. There are hence no obvious barriers to quantifying parameter uncertainty in LCA studies. More standardized methods based upon context-specific data that strike the right balance between comprehensiveness and usability are, however, necessary in order to better account for both the shared and unique sources of uncertainty in attributional and consequential LCAs. More frequent and comprehensive reporting of uncertainty analysis is strongly recommended for published LCA studies. Improved practices should be encouraged and supported by peer-reviewers, editors, LCI databases and LCA software developers.
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There is increasing interest in the study of Life Cycle Assessment (LCA) of buildings, which entails an estimate of the potential environmental impacts and resource use of buildings. This is driven by increasing awareness of the environmental impact of buildings, as well as the emergence of enabling tools for their assessment. There are review articles on building LCA (see Table 1) but none focuses on the challenges of building LCA, ongoing studies and potential solutions to address the challenges. The aim of this paper is to provide an up-to-date systematic review of life cycle assessment of buildings, and to discuss the major challenges in building LCA, ongoing studies and potential solutions to resolve the identified issues. The methodology involves a detailed literature review to provide an overview of existing studies in building LCA, and a systematic selection and study of review articles/books to investigate the benefits and challenges of building LCA. A summary of the research outputs and recommended further studies on building LCA are outlined in the conclusion section. The major challenges in building LCA were identified as data intensity and quality, subjectivity in environmental impact characterization and valuation, inadequate definition of functional units, assumptions for building life span and service life, lack of procedure for system boundaries, lack of uncertainty analysis, and limitation as a decision-making tool. In addition to discussing ongoing studies to address the issues, this study also proposes research trajectories to resolve the major challenges identified in building LCA.
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Purpose We hypothesize that the current heated scientific debate on bioenergy sustainability is fuelled by flaws in the interpretation phase of bioenergy LCA studies rather than by the lack of studies or shared methodologies. The interpretation phase is the key step in LCA studies, which guarantees their quality and consistency and gives meaning to the work carried out by delivering results that are consistent with the defined goal and scope, which reach conclusions, and explain limitations. Methods To test our hypothesis, we selected the 100 most cited articles found in Scopus utilizing a query to include most of the relevant works on LCA of bioenergy. The rationale underpinning the choice of the most cited articles is that these are presumably the most influential. A further screening identified off-topic articles, reviews, and methodological papers, which were discarded. We have also checked whether the articles analysed referred to the ISO standards. The study is organized as a reasoned and parametrized review in which we assess the methodological approach of the studies, rather than the results obtained. Results and discussion We find that overlooking some of the fundamental steps in the interpretation phase in bioenergy LCA is a rather common practice. Although most of the studies referred to the ISO standards, the identification of issues, their framing with sensitivity analyses, and the identification and reporting of limitations, which are all needed to comply with ISO14044 standards, are often neglected by practitioners. The most problematic part of the interpretation phase is the consistency check. In most cases, the assessment framework built is not apt at answering the question set in the goal. Limitations are properly identified and reported only in few studies. Conclusions We conclude that in many studies either the conclusions and recommendations drawn are not robust because the inventory and the impact assessment phases are not consistent with the goal of the study, or the conclusions and recommendations go well beyond what the limitations of the study would allow. In our opinion, these flaws in the interpretation phase of influential LCA studies are among the responsible factors that continue to fuel the debate around the sustainability of bioenergy. We report a set of recommendations both for LCA practitioners and for users to guide the LCA practitioners in properly organizing and reporting their work, and to facilitate the readers in understanding and evaluating the significance and applicability of the results presented.
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Purpose The goal of this study was to provide a holistic, reliable, and transparent comparison of battery electric vehicles (BEVs) and fuel cell electric vehicles (FCVs) regarding their environmental impacts (EI) and costs over their whole life cycle. The comprehensive knowledge about EI and costs forms the basis on which to decide which technology should be favored for the future of mobility. Methods Therefore, a holistic and transparent comparative life cycle assessment (LCA), using the ReCiPe 2016 method, and a life cycle costing were conducted. Special attention was paid to the fuel supply infrastructure for BEV and FCV as these have not been sufficiently considered in previous research. The required infrastructure was calculated for six million electric vehicles (EVs) and the EI and costs were allocated proportional on the functional unit of 1 km driven with an EV. Different scenarios regarding electricity mix, range of the BEV, and vehicle lifetime were calculated. In order to ensure transparency, all inventories and calculations were published in the attached Electronic supplementary material (ESM). Results and discussion Detailed results were presented for the impact categories global warming potential (GWP), human toxicity potential non-carcinogenic (HTPnc), surplus ore potential (SOP), and particulate matter formation potential (PMFP). Aggregated results for all midpoint impact categories of the ReCiPe method can be found in the ESM. It was shown that BEVs achieve lower EI than FCVs in most impact categories (e.g., GWP: BEV: 1.40E-01, FCV: 1.68E-01 kg CO2-eq./km) and that the total costs of ownership are as well lower for BEVs (68,900 € vs. 130,100 €). Further, it was found that the fuel supply infrastructure—without electricity supply—contributes a considerable amount to the overall impact per kilometer driven (e.g., 3.7% and 3.3% of the GWP for BEV and FCV, respectively). Conclusions Considering mid-size vehicles like the VW e-Golf, it was concluded that BEVs have today a better environmental and financial performance than FCVs. However, the range of the BEV is lower than the range of the FCV (200 vs. 530 km) and both technologies have different stages of maturity. Moreover, the study showed that the fuel supply infrastructure is an important contributor to the overall life cycle impacts and that it is therefore indispensable to include the infrastructure in LCA of electric vehicles. Based on the results, recommendations to utilize the advantage of both BEV (high energy efficiency, lower costs) and FCV (long-distance capability) were made.
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Purpose This paper presents the regionalized water scarcity characterization factors (CFs) of the available water remaining (AWARE) model, which was found by a previous study, on the water scarcity in Brazil, to be the most indicative characterization model for the water-scarce regions in Brazil. We used the national database and hydrographic delimitations defined by the National Water Agency (Agência Nacional de Águas — ANA) to generate the regionalized AWARE BR CFs. Methods The CFs were regionalized by hydrographic delimitations used by ANA: (i) State Hydrographic Units (SHU) and (ii) Hydrographic Regions (HR). These AWARE BR CFs were compared with the factors originally proposed by WULCA (2018) and with the Scarcity Index used by ANA to identify the scarcest regions in the country. Finally, the AWARE and AWARE BR factors were applied to a case study of Brazilian melons, evaluating the regionalization effects on the results of water scarcity analysis. Results and discussion The AWARE BR CFs demonstrate most consistency with the regions recognized by ANA to have water scarcity problems, such as the semiarid region. Approximately 12% of the SHUs exhibited maximum water scarcity (CF = 100) during the entire year, while 11% presented minimum scarcity factors (CF = 0.1). The comparison of hydrologic data from ANA with those from WaterGAP indicated that water availability was overestimated in WaterGAP, while demand was underestimated in different basins. The comparison of AWARE BR CFs with ANA Scarcity Index values indicated more similarity (smaller residual error) than the comparison of AWARE BR CFs with AWARE. The case study regarding the impact of water scarcity on melons showed a significant difference between characterization factors and, consequently, in the values of impact. Conclusions AWARE BR factors generated with national characterization data are adapted to the different regions of Brazil, exhibiting higher sensitivity to the semiarid region. This regionalization provided a more accurate representation of the scarcity in smaller basins located in larger basins, characterized by large climate variation.
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The wine production constitutes an important sector for the Italian economy. Most of the wine producers are associated in local consortiums, which include small family companies involved in the production of similar products. This study aims to investigate the implementation of circular economy opportunities in the wine production chain. In particular, the reuse of glass bottles in the Piceno wine consortium (central Italy) has been analyzed to quantify the potential environmental benefits. The standard Life Cycle Assessment (LCA) methodology has been used to compare the standard scenario (recycle of glass) against the circular scenario (cleaning and reuse of bottles within the local consortium). Results demonstrate that the reuse of glass bottles leads to relevant benefits in all the considered impact categories (ReCiPe Midpoint method). The avoided use of virgin glass offsets the additional resources (e.g. energy) consumed during the cleaning of used bottles.
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In this study, material flow analysis (MFA) is applied to quantify and reduce the obstacles for advancing a circular economy (CE) of platinum (Pt) from catalytic converters (CC) in Europe. First, the value chain and related stakeholders are mapped out in an MFA‐like model to both facilitate the assessment of stocks and flows, and get a comprehensive view of potential action levers and resources to close‐the‐loop. Then, through the cross analysis of numerous data sources, two MFA are completed: (i) one general MFA, and (ii) one sector‐specific MFA, drawing a distinction between the fate of Pt from (a) light‐duty vehicles, under the European Union's End of Life Vehicle Directive 2000/EC/53, and (b) heavy‐duty and off‐road vehicles. Key findings reveal a leakage of around 15 tons of Pt outside the European market in 2017. Although approximately one quarter of the losses are due to in‐use dissipation, 65% are attributed to insufficient collection and unregulated exports. Comparing the environmental impact between primary and secondary production, it has been estimated that halving the leakage of Pt during usage and collection could prevent the energetic consumption of 1.3 × 10^3 TJ and the greenhouse gases emission of 2.5 × 10^2 kt CO2 eq. Through the lens of circularity indicators, activating appropriate action levers to enhance the CE performance of Pt in Europe is of utmost importance in order to secure future production of new generations of CC and fuel cells. Moreover, the growing stockpile of Pt from CC in use indicates the need for better collection mechanisms. Also, the CC attrition during use and associated Pt emissions in the environment appears non‐negligible. Based on the scarce and dated publications in this regard, we encourage further research for a sound understanding of this phenomenon that can negatively impact human health.
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As one quarter of global energy use serves the production of materials, the more efficient use of these materials presents a significant opportunity for the mitigation of greenhouse gas (GHG) emissions. With the renewed interest of policy makers in the circular economy, material efficiency (ME) strategies such as light-weighting and downsizing of and lifetime extension for products, reuse and recycling of materials, and appropriate material choice are being promoted. Yet, the emissions savings from ME remain poorly understood, owing in part to the multitude of material uses and diversity of circumstances and in part to a lack of analytical effort. We have reviewed emissions reductions from ME strategies applied to buildings, cars, and electronics. We find that there can be a systematic trade-off between material use in the production of buildings, vehicles, and appliances and energy use in their operation, requiring a careful life cycle assessment of ME strategies. We find that the largest potential emission reductions quantified in the literature result from more intensive use of and lifetime extension for buildings and the light-weighting and reduced size of vehicles. Replacing metals and concrete with timber in construction can result in significant GHG benefits, but trade-offs and limitations to the potential supply of timber need to be recognized. Repair and remanufacturing of products can also result in emission reductions, which have been quantified only on a case-by-case basis and are difficult to generalize. The recovery of steel, aluminum, and copper from building demolition waste and the end-of-life vehicles and appliances already results in the recycling of base metals, which achieves significant emission reductions. Higher collection rates, sorting efficiencies, and the alloy-specific sorting of metals to preserve the function of alloying elements while avoiding the contamination of base metals are important steps to further reduce emissions.
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Information and communication technology (ICT) is often considered a technology for reducing environmental emissions by increasing energy and resource efficiencies of processes. However, due to other effects of ICT, such as rebound and induction effects, the net benefits of ICT in terms of environmental impact are by no means assured. Even though the relevance of indirect or higher order effects has become a well-known issue in recent years, their environmental assessment remains controversial. Life cycle assessment (LCA) is one of the most established environmental assessment methods for modelling the environmental effects of goods and services throughout their life cycle. Although LCA is traditionally rather product-focused, there exist also LCA-based approaches to assess higher order effects of technology replacement and optimization. This paper examines whether and how LCA case studies on environmental effects of ICT already take into account related higher order effects. A systematic review of scientific literature published since 2005 has been conducted and 25 case studies were analyzed in detail. The following research questions were addressed: i) Which products are assessed? ii) Which higher order effects of ICT are considered; and iii) how is the integration of higher order effects methodically realized? The results show that few case studies were concerned with the environmental effects of the introduction of ICT services in commerce, telework and monitoring and control. Most studies investigated the substitution of certain media with electronic devices or digital services. It was found that technology-based higher order effects, such as optimization and substitution, are usually included in the assessment by choosing comparative study designs, while user-related higher order effects, such as rebound effects and induction effects, are less often considered. For the latter effects, methodological integration was mainly provided by scenario modelling and sensitivity analysis. Overall, most studies chose an attributional LCA approach. It can be concluded from the results that, in particular, user-related effects such as rebound effects have not yet been frequently included in the environmental assessment of ICT. The identified research gaps include in particular interdisciplinary approaches on how changing use patterns can be more strongly observed in LCA.
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Purpose This paper addresses the need for a globally regionalized method for life cycle impact assessment (LCIA), integrating multiple state-of-the-art developments as well as damages on water and carbon areas of concern within a consistent LCIA framework. This method, named IMPACT World+, is the update of the IMPACT 2002+, LUCAS, and EDIP methods. This paper first presents the IMPACT World+ novelties and results and then analyzes the spatial variability for each regionalized impact category. Methods With IMPACT World+, we propose a midpoint-damage framework with four distinct complementary viewpoints to present an LCIA profile: (1) midpoint impacts, (2) damage impacts, (3) damages on human health, ecosystem quality, and resources & ecosystem service areas of protection, and (4) damages on water and carbon areas of concerns. Most of the regional impact categories have been spatially resolved and all the long-term impact categories have been subdivided between shorter-term damages (over the 100 years after the emission) and long-term damages. The IMPACT World+ method integrates developments in the following categories, all structured according to fate (or competition/scarcity), exposure, exposure response, and severity: (a) Complementary to the global warming potential (GWP100), the IPCC Global Temperature Potentials (GTP100) are used as a proxy for climate change long-term impacts at midpoint. At damage level, shorter-term damages (over the first 100 years after emission) are also differentiated from long-term damages. (b) Marine acidification impact is based on the same fate model as climate change, combined with the H⁺ concentration affecting 50% of the exposed species. (c) For mineral resources depletion impact, the material competition scarcity index is applied as a midpoint indicator. (d) Terrestrial and freshwater acidification impact assessment combines, at a resolution of 2° × 2.5° (latitude × longitude), global atmospheric source-deposition relationships with soil and water ecosystems’ sensitivity. (e) Freshwater eutrophication impact is spatially assessed at a resolution grid of 0.5° × 0.5°, based on a global hydrological dataset. (f) Ecotoxicity and human toxicity impact are based on the parameterized version of USEtox for continents. We consider indoor emissions and differentiate the impacts of metals and persistent organic pollutants for the first 100 years from longer-term impacts. (g) Impacts on human health related to particulate matter formation are modeled using the USEtox regional archetypes to calculate intake fractions and epidemiologically derived exposure response factors. (h) Water consumption impacts are modeled using the consensus-based scarcity indicator AWARE as a proxy midpoint, whereas damages account for competition and adaptation capacity. (i) Impacts on ecosystem quality from land transformation and occupation are empirically characterized at the biome level. Results and discussion We analyze the magnitude of global potential damages for each impact indicator, based on an estimation of the total annual anthropogenic emissions and extractions at the global scale (i.e., “doing the LCA of the world”). Similarly with ReCiPe and IMPACT 2002+, IMPACT World+ finds that (a) climate change and impacts of particulate matter formation have a dominant contribution to global human health impacts whereas ionizing radiation, ozone layer depletion, and photochemical oxidant formation have a low contribution and (b) climate change and land use have a dominant contribution to global ecosystem quality impact. (c) New impact indicators introduced in IMPACT World+ and not considered in ReCiPe or IMPACT 2002+, in particular water consumption impacts on human health and the long-term impacts of marine acidification on ecosystem quality, are significant contributors to the overall global potential damage. According to the areas of concern version of IMPACT World+ applied to the total annual world emissions and extractions, damages on the water area of concern, carbon area of concern, and the remaining damages (not considered in those two areas of concern) are of the same order of magnitude, highlighting the need to consider all the impact categories. The spatial variability of human health impacts related to exposure to toxic substances and particulate matter is well reflected by using outdoor rural, outdoor urban, and indoor environment archetypes. For “human toxicity cancer” impact of substances emitted to continental air, the variability between continents is of two orders of magnitude, which is substantially lower than the 13 orders of magnitude total variability across substances. For impacts of water consumption on human health, the spatial variability across extraction locations is substantially higher than the variations between different water qualities. For regionalized impact categories affecting ecosystem quality (acidification, eutrophication, and land use), the characterization factors of half of the regions (25th to 75th percentiles) are within one to two orders of magnitude and the 95th percentile within three to four orders of magnitude, which is higher than the variability between substances, highlighting the relevance of regionalizing. Conclusions IMPACT World+ provides characterization factors within a consistent impact assessment framework for all regionalized impacts at four complementary resolutions: global default, continental, country, and native (i.e., original and non-aggregated) resolutions. IMPACT World+ enables the practitioner to parsimoniously account for spatial variability and to identify the elementary flows to be regionalized in priority to increase the discriminating power of LCA.
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Improving the circularity of our economy calls for easily quantifiable metrics that allow us to track our progress towards circularity. We propose the use of a material quality indicator based on the energy use of recycled products versus their counterparts produced from primary material inputs only. We argue that such an indicator can cover at least the environmental dimension of the circular economy in a sufficient way and is therefore useful for the assessment of the circularity of our economy.
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Significance The cumulative radiative forcing (CRF), an integral of radiative forcing over a given time, is used to calculate the contribution to the global mean net radiative forcing due to greenhouse gases and aerosols from various regions. For every region, the commitment to future radiative forcing from emissions already in the atmosphere is larger than that to date. For individual regions, the CRF is near zero during rapid industrialization and it increases when air-quality regulations come in and/or exponential growth ceases, a pattern repeated by North America, Europe, and China. The relative contributions from regions depends more on when the contributions are compared (e.g., now or 2100) and development scenarios than the metric used (i.e., CRF, ocean heat content, or temperature).
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Transportation represents one of the major contributors to several environmental burdens such as Green-House-Gas (GHG) emissions and resource depletion. Considering the European Union, light duty vehicles are responsible for roughly 10% of total energy use and air emissions. As a consequence, the need for higher fuel/energy efficiency in both conventional and electric cars has become urgent and the efforts across industrial and research players have proposed a range of innovative solutions with great potential. This study presents a comparative Life Cycle Assessment of Internal Combustion Engine (ICE) and electric vehicles. The analysis follows a “from cradle-to-grave” approach and it captures the whole Life-Cycle (LC) of the car subdivided into production, use and End-of-Life stages. The inventory is mainly based on primary data and the assessment takes into account a wide range of impact categories to both human and eco-system health. The eco-profile of the different vehicle configurations is assessed and the main environmental hotspots affecting conventional and electric cars are identified and critically discussed. The dependence of impacts on LC mileage is investigated for both propulsion technologies and the break-even point for the effective environmental convenience of electric car is determined considering several use phase electricity sources. The analysis is completed with a comparison of GHG emissions with the results of previous LCA studies.
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Purpose There are specific effects of emissions in high altitude, which lead to a higher contribution of aviation to the problem of climate change than just the emission of CO2 from burning fuels. The exact relevance is subject to scientific debate, but there is a consensus that aircrafts have an impact that is higher than just their contribution due to the direct CO2 emissions. The gap between this scientific knowledge on the one side and the missing of applicable GWP (global warming potential) factors for relevant emissions on the other side are an important shortcoming for life cycle assessment (LCA) or carbon footprint (CF) studies which aim to cover all relevant environmental impacts of the transport services investigated. Methods In this paper, the state of the art concerning the accounting for the specific effects of aircraft emissions in LCA and CF studies is discussed. Therefore, the relevant literature was evaluated, and practitioners were asked for the approaches used by them. Results and discussion Five major approaches are identified ranging from an RFI (radiative forcing index) factor of 1 (no factor at all) to a factor 2.7 for the total aircraft CO2 emissions. If only emissions in the higher atmosphere are considered, RFI factors between 1 and 8.5 are used or proposed in practice. Conclusions For the time being, an RFI of 2 on total aircraft CO2 (or 5.2 for the CO2 emissions in the higher atmosphere if using present models in ecoinvent) is recommended to be used in LCA and CF studies because it is based on the latest scientific publications; this basic literature cannot be misinterpreted. Furthermore, it is also recommended by some political institutions. These factors can be multiplied by the direct CO2 emissions of the aircraft to estimate the total global warming potential.
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: Life Cycle assessments (LCAs) on electric mobility are providing a plethora of diverging results. 44 articles, published from 2008 to 2018 have been investigated in this review, in order to find the extent and the reason behind this deviation. The first hurdle can be found in the goal definition, followed by the modelling choice, as both are generally incomplete and inconsistent. These gaps influence the choices made in the Life Cycle Inventory (LCI) stage, particularly in regards to the selection of the electricity mix. A statistical regression is made with results available in the literature. It emerges that, despite the wide-ranging scopes and the numerous variables present in the assessments, the electricity mix’s carbon intensity can explain 70% of the variability of the results. This encourages a shared framework to drive practitioners in the execution of the assessment and policy makers in the interpretation of the results.
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Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels. By using a worldwide agricultural model to estimate emissions from land-use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products.
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Purpose This article aims to explore how different assumptions about system boundaries and setting of baselines for forest growth affect the outcome of climate impact assessments of forest products using life cycle assessment (LCA), regarding the potential for climate impact mitigation from replacing non-forest benchmarks. This article attempts to explore how several assumptions interact and influence results for different products with different service life lengths. Methods Four products made from forest biomass were analysed and compared to non-forest benchmarks using dynamic LCA with time horizons between 0 and 300 years. The studied products have different service lives: butanol automotive fuel (0 years), viscose textile fibres (2 years), a cross-laminated timber building structure (50 years) and methanol used to produce short-lived (0 years) and long-lived (20 years) products. Five calculation setups were tested featuring different assumptions about how to account for the carbon uptake during forest growth or regrowth. These assumptions relate to the timing of the uptake (before or after harvest), the spatial system boundaries (national, landscape or single stand) and the land use baseline (zero baseline or natural regeneration). Results and discussion The implications of using different assumptions depend on the type of product. The choice of time horizon for dynamic LCA and the timing of forest carbon uptake are important for all products, especially long-lived ones where end-of-life biogenic emissions take place in the relatively distant future. The choice of time horizon is less influential when using landscape- or national-level system boundaries than when using stand-level system boundaries, and has greater influence on the results for long-lived products. Short-lived products perform worse than their benchmarks with short time horizons whatever spatial system boundaries are chosen, while long-lived products outperform their benchmarks with all methods tested. The approach and data used to model the forest carbon uptake can significantly influence the outcome of the assessment for all products. Conclusions The choices of spatial system boundaries, temporal system boundaries and land use baseline have a large influence on the results, and this influence decreases for longer time horizons. Short-lived products are more sensitive to the choice of time horizon than long-lived products. Recommendations are given for LCA practitioners: to be aware of the influence of method choice when carrying out studies, to use case-specific data (for the forest growth) and to communicate clearly how results can be used.
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The 1.5 °C mitigation challenge for urban areas goes far beyond decarbonizing the cities’ energy supply and needs to enable and incentivize carbon-free everyday living. Reviewing recent literature, we find that dense and mixed urban form enables lower direct emissions from mobility and housing, while income is the major driver of total household carbon footprints; importantly, these effects are not linear. The available urban infrastructure, services and societal arrangements, for example on work, all influence how households use their time, which goods and services they consume in everyday life and their subsequent carbon footprints and potential rebound effects. We conclude that changes in household consumption, time use and urban form are crucial for a 1.5 °C future. We further identify a range of issues for which a time use perspective could open up new avenues for research and policy.
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Used lubricating oils (ULOs) represent a serious problem for environment and human health due to the presence of highly harmful contaminants, being mandatory an adequate management based on efficient collection systems and treatment processes. Within this work, the environmental and energy performance of a re-refining process for ULOs upgrading is evaluated. The proposed regeneration process is based on the extraction of organic contaminants with liquid propane followed by a cascade of three consecutive distillation stages (two under atmospheric conditions and an additional one under vacuum). This process operates at plan scale in Spain recovering base oil for reuse. All the operations were simulated using Aspen Plus 8.6 and environmental issues and performance was determined by LCA, considering global warming potential, cumulative energy demand, acidification and toxicity as impacts categories. Results show that the whole upgrading process generates up to 363 kg-eq CO2/tonne base oil (mainly associated with distillations heating requirements) and it consumes 6144 MJ/tonne base oil. Vacuum distillation is the most important contributor to acidification and toxicity, due to heating and electricity requirements of the column. These parameters were compared for upgraded base oil and refinery lubricant oil, and results suggested that great environmental impacts can be reduced by recycling oil. Finally, different LCA scenarios were considered by partitioning impacts among base oil and plant by-products, using mass flow and economic criteria. Regardless the impacts allocation method, results clearly indicate that manufacturing base oil by ULOs recycling is a more environmental friendly option than the conventional refinery process.
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Life cycle assessment (LCA) assesses the environmental impacts of products from cradle to grave. It is also possible to assess parts of the life cycle. Available peer-reviewed LCAs dealing with microalgae-based products and processes are reviewed. In processes that require extraction of dry algae, the combined harvesting, drying, and extraction steps are associated with relatively large environmental impacts. In addition, the cultivation stage has been identified as linked to relatively large environmental impacts. Proteins derived from cyanobacteria tend to have larger estimated life cycle environmental impacts than proteins derived from cultivated terrestrial plants such as maize and soybean. Microalgal biomass-based feed for carnivorous fish might have a lower life cycle environmental burden than conventional fish meal. Whether commercial microalgal fuels will have a climate benefit compared with fossil fuels appears to be uncertain. The energetic return on energy invested (EROI) of all microalgal fuels for which peer-reviewed LCAs are available does not meet the criterion of 5–8, which would allow for widespread application.
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This review assesses the state-of-the-art in comparative Life Cycle Assessment of fossil-based and bio-based polymers. Published assessments are critically reviewed and compared to the European Union Product Environmental Footprint (EU PEF) standards. No published articles were found to fully meet the standards, but the critical review method was used to classify the articles by their level of compliance. 25 articles partially met the PEF standards, giving 39 fossil-based and 50 bio-based polymer case results. Ultimately, it was possible to compare seven bio-based polymers and seven fossil-based polymers across seven impact categories (energy use, ecotoxicity, acidification, eutrophication, climate change, particulate matter formation and ozone depletion). Significant variation was found between polymer types and between fossil-based and bio-based polymers, meaning it was not possible to conclusively declare any polymer type as having the least environmental impact in any category. Significant variation was also seen between different studies of the same polymer, for both fossil-based and bio-based polymers. In some cases this variation was of the order of 400%. Results suggest that a large part of this variation is related to the Life Cycle Assessment methodologies applied, particularly in the end-of-life treatment, the use of credits for absorbed Carbon Dioxide, and the allocation of multifunctional process impacts. The feedstock source and processing method assumed for bio-based polymers was also a major sources of variation. The challenges of Life Cycle Assessment, particularly in a complex, geographically diverse and young industry like bio-based polymers, are recognised. It is proposed that the PEF standards should be adopted more widely in order to homogenise the methods used and allow meaningful comparison between LCA studies on fossil-based and bio-based polymers, and between studies of the same polymers.
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During building design and especially in early stages, important decisions influencing the lifecycle-based energy demand of buildings are made. Life Cycle Energy Assessment (LCEA) is used to evaluate this energy demand already in early stages of design. However, at that point, the building design and the related information can quickly change and are subject to potentially large uncertainty. This uncertainty in building information influences the LCEA and therefore decisions taken by the designer. Due to the uncertainty, it is difficult to distinguish between the performance of different design variants to decide for the best option. This study presents a method to perform LCEA and to assess and consequently strategically reduce the influence of uncertainties in buildings’ information on the LCEA in early design stages. Uncertainty analysis is used to assess the influence of uncertainty on LCEA and to prioritize decisions to reduce uncertainty. The method is embedded in a multi-Level of Development (LOD) modelling approach covering the development of the building during the early stages of design. The method is applied to seven different building shapes as a proof of concept. It is concluded that the method renders valid results to assess the project-specific uncertainty in LCEA results.
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European and United States' (U.S.) regulatory schemes mandate the use of biofuels based on estimates of life cycle GHG emissions that indicate their environmental superiority compared with conventional fuels. This paper analyzes the quality of the activity data used in calculating these estimates for Brazilian sugarcane and U.S. corn ethanol, in terms of completeness, reliability, and transparency. The findings demonstrate that it is impossible to determine the completeness of the data because the regulation's texts and related documents, and their sources fail to provide information on the representativeness or origins of the data. Moreover, there is no transparency about the sample from which data is extracted. To obtain this information it is necessary to review the literary sources referenced in the regulation's documents. Among the 37 sources of data examined in this analysis, 23 are no longer available, and only 3 sources contain information allowing for the characterization of the adequacy of the sample. In addition, none of the data items analyzed were subject to a verification process. These findings highlight the urgent need to modify biofuel regulation to set minimum standards for data quality and the reporting of data sources, paying particular attention to default activity data.
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Approximately 88 Mt of food are wasted every year in the European Union and are responsible for 15–16% of the environmental impact of its entire food value chain. The United Nations’ Sustainable Development Goal (SDG) 12.3 demands per capita global food waste (FW) at the retail and consumer levels to be halved by 2030. This study aims to identify whether the SDG 12.3 is realistic and to assess the associated climate, biodiversity, and aggregated environmental benefits from FW prevention in the food service sector. The FW reduction potential is assessed in 13 case studies that implemented measures for reduction. We estimate status quo avoidable FW at 108 g/meal (13% of purchased food), causing 238 g CO2-eq/meal. FW reduction achieved in the case studies ranges from 32% of status quo in the education subsector to 62% in the business subsector. On average, a 38% decrease in FW amounts reduces climate impacts of FW by 41% and biodiversity impacts by 30%. In an extended reduction scenario, food services use 50% non-marketable vegetables that would otherwise be wasted throughout the food value chain. In combination, FW amounts are reduced by 70%. We conclude that the SDG 12.3 is realistic and can even be exceeded in the long term. Initial investments and political support are important to reach individual food services.
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Techno-economic analysis and life cycle assessments are crucial for any processes to be sustainable using the tri-fold metrics including technical feasibility, economic viability, and environmental sustainability. Anaerobic digestion is portrayed as one of the mature technologies for handling solid waste management and bioenergy generation. Nonetheless, a clear assessment of the tri-fold sustainability metrics is not available yet and this review attempts to address this knowledge gap. Important problems in techno-economic analysis and life cycle assessments such as assumptions used, extrapolation of research data, robustness and reproducibility of results, the openness of materials were discussed. Anaerobic digestion helps in treating organic wastes that could be used for different purposes including electricity, vehicle fuel, natural gas substituent, heating, and cooking fuel. However, sustainability in terms of technology, economics and environment remains the question for it to be industrialized.
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Economy-wide rebound effects may undermine climate policies relying on energy efficiency improvements. However, available rebound estimates diverge widely. We illustrate the crucial role of model assumptions of household heterogeneity and elasticities. A computable general equilibrium model of the Austrian economy incorporates multiple household groups with heterogeneous preferences and analyzes how improving efficiency by 10% affects household fossil fuel consumption. In the base model, economy-wide rebound is 65%; different household groups show direct rebound of 8-12%; thus, economy-wide rebound is mainly advanced by indirect rebound. A sensitivity analysis using Monte Carlo simulation varies elasticities between household groups, namely substitutability between material and energy goods, and between different energy goods. In 160 simulation runs, the economy-wide rebound emerges as rather robust. By contrast, direct rebound varies widely among household groups and attains 30%, where reciprocal feedback between groups builds up. In the base model, a fossil fuel tax rate of 43% neutralizes the economy-wide rebound. When elasticities in 180 simulation runs are varied, this tax rate spans from 15% to 80%. Thus, rebound estimates and derived policy advice, such as specific rates and numbers, should be treated with great caution, unless elasticity parameters are reliable and account for heterogeneous consumer preferences.
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The circular economy has emerged as an important approach in addressing how society can use its resources more efficiently. Theoretical advancements in the circular economy have yielded benefits for both practice and policymaking. However, if the eco-efficiency of resource use is to be improved, then certain challenges that face the circular economy must be resolved. One of these challenges concerns the rebound effect. By investigating resource flow with a circular (rather than linear) system, as well as within a producer-producer (rather than producer-consumer) type of relationship, we identify a rebound effect that we term 'symbiotic rebound'. We differentiate it from other forms of rebound effect on the basis of its main driver: Opportunity costs drive a higher than expected use of resources in a circular economy, rather than the usual driver of 'demand', as found in other types of rebound. In identifying, describing, and illustrating a symbiotic rebound effect, we make two contributions: first to the rebound literature, and second to theory development on the circular economy.
Article
Traditional liquid fuels production is heavily dependent on crude oil. Due to the conflict between liquid fuels demand and shortage of crude oil supply, Chinese government has begun to develop alternative feedstocks. In this paper, we carried out comparative analysis of coal to liquid fuels (CTF) and oil shale to liquid fuels (STF) from the perspectives of life cycle GHG emissions and water consumption. Results show that the life cycle GHG emissions of the CTF and STF routes are 15.54 and 9.82 t CO2-eq/t-fuels, which are greatly higher than that of oil to liquid fuels (OTF) route (6.36 t CO2-eq/t-fuels). The life cycle water consumption of the CTF route is the largest, 12.98 t/t-fuels, followed by the STF route, 7.69 t/t-fuels, and the OTF route 1.18 t/t-fuels. Therefore, taking measures to conduct the reduction of GHG emissions and water consumption is the key for the CTF. Three feasible suggestions are proposed as follows: (1) integrating coal and hydrogen-rich gas to produce liquid fuels; (2) optimizing the heat exchange and water networks; and (3) mobilizing the enthusiasm of reduction of emissions and saving water by implementing carbon tax and raising water price.
Article
Large quantities of residual forest-based biomass, including harvesting and sawmill residues, are available in British Columbia, Canada. They can be used to generate bioenergy. Currently, harvesting residues are burned to reduce fire hazard, and private and remote sawmills’ residues are either burned or landfilled. While previous studies assessed the impact of bioenergy production from residual forest-based biomass on global warming, this life cycle assessment includes a comprehensive set of ten impact categories. Adopting a case study in a region in British Columbia, a life cycle model is applied to three locations considering four combustion and gasification technologies with different capacities (0.5 MW, 2 MW, 3 MW and 5 MW) and product outputs (electricity and/or heat). Most bioenergy supply chain scenarios showed improved environmental performance due to avoided uncontrolled combustion of residues and avoided fossil fuel combustion, particularly in the categories of acidification (+1% to -71%), eutrophication (-2% to -85%), fossil resource depletion (-2% to -84%), respiratory effects (0% to -96%), and photochemical ozone formation (+3% to -59%). Benefits were larger at locations dependent on fossil energy compared to locations dependent on hydropower. In contrast, ecotoxicity values increased in most scenarios (+460% to -11%), due to wood ash disposal. Results confirmed conversion efficiency and wood ash disposal as influencing factors in bioenergy supply chains for the investigated region, but showed a minor influence of the feedstock procurement distance. Moreover, the results emphasized the high contribution of uncontrolled burnings to the overall environmental impact of the forest biomass supply chains.
Article
In this paper, the contributions to emissions to air related to traffic infrastructure and terminals are analysed for freight transport with different modes. Data on emissions per km road or railway from existing LCA reports are adapted to a selection of road types and one type of railway line. The presented data are for air pollutants, use of primary energy and emissions of green-house gases divided into construction, maintenance and operation phases. These data are then allocated to the traffic-work produced on the infrastructure during its life span. Different allocation methods are suggested for the separate LCA-phases. The research has a focus on freight transport, why data are presented as emissions per vehicle-km for a number of truck and train types. For ports and airports, data are available per tonne of goods over quay or in- and outgoing. These results are then used to calculate the emissions added for infrastructure for freight transport chains. Examples are given showing the magnitude of emissions originating from infrastructure that can be added to tailpipe and other upstream emissions, e.g. fuel and vehicle production. In relation to tailpipe emissions the CO2 emissions from infrastructure is typically 1–7% for road and around 17% for rail. For air and sea the results will vary significantly; for typical intra-Europe routes we find a contribution from infrastructure of about 3% for air and 21–34% for sea, in relation to emissions from the vessels.
Article
This paper proposes a case study on Belgium in which externalities and external costs of inland freight transport modes in Belgium are compared for the year 2012. The well-known Life Cycle Assessment methodology is used to identify the updated specific Belgian externalities related to three categories of negative impacts: climate change, photochemical ozone formation and particulate matter formation. The obtained values of externalities are then compared to the related external cost values. The objective is to determine if these two tools can be used interchangeably. We find that road transport has the maximum impact for every environmental impact indicator, with rail freight transport presenting the minimum one. We identify that each category of negative impact on the environment does not represent the same percentage of global externalities and external costs. In the analysis of the environmental impact per mode, it is observed that, when external costs are considered instead of externalities, the impact of road transport is slightly increased compared to both impacts of rail and inland waterways. Using externalities and average external costs interchangeably for estimating the impact of specific transport categories on the environment may thus lead to different results and different related policies.
Article
Comparative life-cycle assessment (LCA) of pharmaceutical drugs would enable clinicians to choose alternatives with lower environmental impact from options offering equivalent efficacies and comparable costs. However, life-cycle inventory (LCI) data of individual pharmaceutical drugs is limited to only a few compounds. In this study, we use chemical engineering methods for process scale-up and process design to utilize lab-scale synthesis data, available in patents and other public literature, to generate cradle-to-gate LCI data of 20 commonly used injectable drugs in anesthesia care to calculate their greenhouse gas impact. During the process of building the life-cycle trees of these drugs, missing life-cycle inventories for more than 130 other chemical compounds and pharmaceutical intermediates were accounted for using process-based methods and stoichiometric calculations. The cradle-to-gate GHG emissions of the 20 anesthetic drugs range from 11 kg CO2 eq. for succinylcholine to 3,000 kg CO2 eq. for dexmedetomidine. GHG emissions are positively correlated with the number of synthesis steps in the manufacturing of the drug. The LCI methods and data generated in this work greatly expand the available environmental data on APIs and can serve as a guide for LCA practitioners in future analysis of other pharmaceutical drugs. Most importantly, these LCA results can be used by clinical practitioners and administrators building toward sustainability in the health care sector.
Article
Global population growth and changing diets increase the importance, and challenges, of reducing the environmental impacts of food production. Farmed seafood is a relatively efficient way to produce protein and has already overtaken wild fisheries. The use of protein-rich food crops, such as soy, instead of fishmeal in aquaculture feed diverts these important protein sources away from direct human consumption and creates new environmental challenges. Single cell proteins (SCPs), including bacteria and yeast, have recently emerged as replacements for plant-based proteins in salmon feeds. Attributional life cycle assessment (ALCA) is used to compare salmon feeds based on protein from soy, methanotrophic bacteria, and yeast ingredients. All ingredients are modeled at the industrial production scale and compared based on seven resource use and emissions indicators. Yeast protein concentrate showed drastically lower impacts in all categories compared to soy protein concentrate. Bacteria meal also had lower impacts than soy protein concentrate for five of the seven indicators. When these target meals were incorporated into complete feeds the relative trends remain fairly constant, but benefits of the novel ingredients are dampened by high impacts from the non-target ingredients, Particularly, primary production requirements (PPR) are about equal and constant across all feeds for both analyses since PPR was driven by fishmeal and oil. The bacteria-based feed has the highest climate change impacts due to the use of methane to feed the bacteria who then release carbon dioxide. Overall, the results of this study suggest that incorporating SCP ingredients into salmon feeds can help reduce the environmental impacts of salmon production. Continued improvements in SCP production would further increase the sustainability of salmon farming.
Article
Polyethylene terephthalate (PET) is a common plastic resin used to produce packaging, notably plastic bottles. Most PET bottles are produced from fossil fuel-derived feedstocks. Bio-derived and recycling-based pathways to PET bottles, however, could offer lower greenhouse gas (GHG) emissions than the conventional route. In this paper, we use life-cycle analysis to evaluate the GHG emissions, fossil fuel consumption, and water consumption of producing one PET bottle from virgin fossil resources, recycled plastic, and biomass, considering each supply chain stage. We considered two routes to produce bottles from biomass: one in which all PET precursors (ethylene glycol and teraphthalic acid) are bio-derived and one in which only ethylene glycol is bio-derived. Bio-derived and recycled PET bottles offer both GHG emissions and fossil fuel consumption reductions ranging from 12% to 82% and 13% to 56%, respectively, on a cradle-to-grave basis compared to fossil fuel-derived PET bottles assuming PET bottles are landfilled. However, water consumption is lower in the conventional pathway to PET bottles. Water demand is high during feedstock production and conversion in the case of biomass-derived PET and during recycling in the case of bottles made from recycled PET.
Article
Changes in diet have been proposed as one way to reduce carbon emissions from the food system. But evidence on the implications of changing to low carbon food choices for both diet quality and food affordability are limited in the U.S. The objective of this study was to (a) estimate greenhouse gas emissions (GHGEs) from U.S. household food purchases; (b) examine the source of GHGEs across U.S. food production industries and stages of the supply chain; and (c) show the association between GHGEs and spending by food categories and household sociodemographics. GHGEs from food expenditures made by households participating in the National Household Food Acquisition and Purchase Survey were calculated using Economic Input-Output Life Cycle Assessment. Results indicate that food purchases accounted for 16% of U.S. GHGEs in 2013 and average weekly household GHGEs were 71.8 kg carbon dioxide equivalents per standard adult. 68% of average weekly household GHGEs from food spending came from agriculture and food manufacturing stages of the food supply chain. Industries that produce animal proteins accounted for 30% of average weekly household GHGEs, the largest share of any food industry. Households generating the highest levels of GHGEs spent a significantly larger share of their food budget on protein foods compared to households generating lower levels of GHGEs. White households and those with higher education levels generated more GHGEs from food spending compared to non-white and less educated households. Overall these findings inform the ongoing debate about which diets or food spending patterns in the U.S. are best for mitigating GHGEs in the food system and if they are feasible for consumers to purchase.
Article
The conclusions from life cycle assessment of algal biofuels (e.g., biodiesel, renewable diesel) vary significantly due to both modeling and inherent technological uncertainties. The inherent uncertainties of US-based algal biofuels production were investigated by eliminating modeling uncertainty via comprehensive harmonization through a meta-analysis. Following harmonization, the cumulative fossil energy consumption (MJ/MJ), global warming potential (g CO2-eq/MJ) and water consumption (m³/MJ) of different algal biofuel process trains were investigated through a stochastic life cycle model. By focusing on the inherent differences of current technologies, this study identified (1) the differences in impact results between different process trains (i.e., different combinations of technology choices along the fuel production life cycle), (2) high impact hotspots, and (3) possible low impact process trains, all of which are crucial to further improve the sustainability of algal biofuels. The median (range) values of the three indicators for the most common algal biodiesel process train are 3.5 (2.9–4.2) MJ/MJ, 99 (55–151) g CO2-eq/MJ and 0.08 (0.07–0.09) m³/MJ, with corresponding inter-quartile ranges being 63%, 46% and 43% less than the literature values, respectively. The median (range) values of the three indicators for the most common algae renewable diesel process train are 1.7 (1.4–2.2) MJ/MJ, 84 (60–112) g CO2-eq/MJ and 0.04 (0.03–0.05) m³/MJ, with the corresponding reductions in inter-quartile range by 83%, 83% and 84%, respectively. Although neither of the median global warming potential results for algal biofuels met the mandatory thresholds in the Renewable Fuel Standard (45 g CO2-eq/MJ), it is possible to meet the requirement by integrating low impact technology options into the process trains.
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The intensification of global agriculture has led to a decline in arable land. Globally, agriculture intensification has not only degraded the soil quality but also contributed to increasing the greenhouse gas (GHG) levels. These concerns attract the interest of environmental scientists and academicians to find ways to sequester more carbon (C) in the agricultural soils. Tillage is one method that can affect biological C sequestration and effects the GHG production. The components of GHGs are produced slowly from the soil through the reactions taking place between C and nutrients (nitrogen in particular), which remain present in the soil. An understanding of biological C sequestration processes in agricultural production systems can lead to potentially cost-effective strategies able to mitigate global warming. Globally, the shift in tillage practice from conventional tillage to no-tillage is effectively protecting soils under cropping, improving their quality—or reducing their rate of soil organic matter decline—as well as enhancing the resilience of cropping systems. This review summarizes the current knowledge about no-till technology and its impacts on soil properties related to carbon dynamics and explores the potential role of tillage practices in mitigating climate change.
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The paper presents the study of a Hybrid Photovoltaic/Thermal solar water system installed on the roof of buildings. The conducted analysis focuses on a detailed experimental investigation of both the electrical and thermal behavior, and in addition on the holistic environmental analysis during the complete life cycle of the system. The photovoltaic module, used for electricity production, is connected with a heat recovery unit with circulating fluid flow for cooling, while the extracted heat can be used for domestic hot water provision. The aim of this study is to analyze the energy and environmental performance of arrangements based on natural and forced circulation, and to draw general conclusions for the viability of such systems. The environmental performance of the studied devices was evaluated through a detailed Life Cycle Assessment. The energy analysis proves that hybrid systems are more efficient compared to conventional solar thermal and photovoltaic appliances, while they are less environmentally friendly mainly during their production and installation phases.