No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Biophysical and economic limits to negative CO2 emissions
Abstract
To have a >50% chance of limiting warming below 2 °C, most recent scenarios from integrated assessment models (IAMs) require large-scale deployment of negative emissions technologies (NETs). These are technologies that result in the net removal of greenhouse gases from the atmosphere. We quantify potential global impacts of the different NETs on various factors (such as land, greenhouse gas emissions, water, albedo, nutrients and energy) to determine the biophysical limits to, and economic costs of, their widespread application. Resource implications vary between technologies and need to be satisfactorily addressed if NETs are to have a significant role in achieving climate goals.
... The advantages of ERW include a significant potential for carbon sequestration, a reduced reliance on other net water resources, and the capacity to release ions that promote crop growth during the weathering process. [4][5][6] The potential for ERW technology to sequester CO 2 on a global scale has been estimated by various studies to range from hundreds of millions to billions of tons per year. 7 Furthermore, ERW does not necessitate the use of sophisticated technical equipment and can be implemented in a variety of geographical settings with minimal preparatory work. ...
... Enhanced weathering requires the least amount of land, and estimates of water required per ton of CO 2 removed by enhanced weathering are an order of magnitude lower than those for BECCS (bioenergy, carbon capture, and storage). 5 Table 1 shows global impacts of NETs for the average needed global carbon removals per year in 2100. This may facilitate the large-scale implementation of ERW, as ERW will have some positive effects on soils and crops, and the cost of synergies will be lower than that of capturing and sequestering CO 2 . ...
... Global impacts of NETs for the average needed global C removals per year in 2100 in 2°C-consistent scenarios, from.5 NET is with lower maximum potential than the BECCS emission requirement of 3.3Gt Ceq per year in 2100; their mean (and maximum potential is given along with their impacts (see Supporting Information). ...
Enhanced rock weathering (ERW) is an emerging negative emission technology (NET) with significant potential for mitigating climate change and improving soil health through the accelerated chemical weathering of silicate minerals. This study adopts a critical research approach to review existing ERW experiments, focusing on the mechanisms of soil improvement and CO₂ sequestration, as well as the economic costs and environmental risks associated with its large‐scale implementation. The results demonstrate that while ERW effectively enhances soil pH and provides essential nutrients for crops, its CO₂ sequestration capacity is highly dependent on variables such as soil type, rock type, application rate, and particle size. Furthermore, the economic feasibility of ERW is challenged by high costs related to mining, grinding, and transportation, and environmental risks posed by the release of heavy metals like Ni and Cr during the weathering process. Notably, significant discrepancies exist between laboratory experiments and field applications, highlighting the need for extensive in‐situ monitoring and adjustment of ERW practices. This study underscores the importance of optimizing ERW strategies to maximize CO₂ sequestration while minimizing environmental impacts. Future research should focus on long‐term field experiments, understanding secondary mineral formation, and refining the application techniques to enhance the overall efficiency and sustainability of ERW. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.
... Removing CO 2 in the projected order of 10 gigatonnes per year or more [3,6] will demand natural and economic resources [9]. CO 2 fixation based on natural processes, such as forestation, BECCS, or enhanced weathering, is associated with high land and resource demand [8,9,10]. ...
... Removing CO 2 in the projected order of 10 gigatonnes per year or more [3,6] will demand natural and economic resources [9]. CO 2 fixation based on natural processes, such as forestation, BECCS, or enhanced weathering, is associated with high land and resource demand [8,9,10]. Biomass plantations also increase the use of freshwater and fertilizers and can offset Here, we assume photovoltaics to power the DAC process stage. ...
... DAC process chains promise higher land use efficiencies than, for example, biomass-based CDR, which may omit adverse climatological and biogeochemical effects [9]. Still, they are technologically immature, cost-intensive, and energy-demanding [5,6,16]. ...
Removing carbon dioxide (CO2) from the atmosphere is required for mitigating climate change. Large-scale direct air capture combined with injecting CO2 into geological formations could retain carbon long-term, but demands a substantial amount of energy, pipeline infrastructure, and suitable sites for gaseous storage. Here, we study Earth system impacts of modular, sun-powered process chains, which combine direct air capture with (electro)chemical conversion of the captured CO2 into liquid or solid sink products and subsequent product storage (sDACCCS). Drawing on a novel explicit representation of CO2 removal in a state-of-the-art Earth system model, we find that these process chains can be renewably powered and have minimal implications for the climate and carbon cycle. However, to stabilize the planetary temperature two degrees above pre-industrial levels, CO2 capturing, conversion, and associated energy harvest demand up to 0.46% of the global land area in a high-efficiency scenario. This global land footprint increases to 2.82% when assuming present-day technology and pushing to the bounds of removal. Mitigating historical emission burdens within individual countries in this high-removal scenario requires converting an area equivalent to 40% of the European Union's agricultural land. Scenarios assuming successful technological development could halve this environmental burden, but it is uncertain to what degree they could materialize. Therefore, ambitious decarbonization is vital to reduce the risk of land use conflicts if efficiencies remain lower than expected.
... For example, pathways that are limiting warming to 1.5°C show a mean increase in forest cover of about 322 (−67 to 890) Mha and a mean increase in cropland area to supply biomass for BECCS of around 199 (56 to 482) Mha in 2050 (IPCC Working Group III, 2022c). The extended use of land and water for tCDR might provoke conflicts with nature conservation or agriculture and might cause deforestation, biodiversity loss, and higher food prices and put a larger pop-ulation at risk of hunger and malnutrition (Creutzig, 2016;Smith et al., 2016;Humpenöder et al., 2018;Roe et al., 2019;Doelman et al., 2020). Thus, not all methods are suitable everywhere globally, and their carbon sequestration potential will evolve differently. ...
... Several trade-offs and side effects occur in connection with tCDR and might limit their efficiency. Previous studies found that the land, water, and fertilizer, especially for firstgeneration bioenergy plants, required by BECCS could exacerbate water stress and pose a risk to food security (Creutzig, 2016;Smith et al., 2016;Boysen et al., 2017;Humpenöder et al., 2018;Roe et al., 2019;Cheng et al., 2022). These negative side effects can be alleviated by, e.g., using crop residues for bioenergy production. ...
The climate mitigation potential of terrestrial carbon dioxide removal (tCDR) methods depends critically on the timing and magnitude of their implementation. In our study, we introduce different measures of efficiency to evaluate the carbon removal potential of afforestation and reforestation (AR) and bioenergy with carbon capture and storage (BECCS) under the low-emission scenario SSP1-2.6 and in the same area. We define efficiency as the potential to sequester carbon in the biosphere in a specific area or store carbon in geological reservoirs or woody products within a certain time. In addition to carbon capture and storage (CCS), we consider the effects of fossil fuel substitution (FFS) through the usage of bioenergy for energy production, which increases the efficiency through avoided CO2 emissions.
These efficiency measures reflect perspectives regarding climate mitigation, carbon sequestration, land availability, spatiotemporal dynamics, and the technological progress in FFS and CCS. We use the land component JSBACH3.2 of the Max Planck Institute Earth System Model (MPI-ESM) to calculate the carbon sequestration potential in the biosphere using an updated representation of second-generation bioenergy plants such as Miscanthus. Our spatially explicit modeling results reveal that, depending on FFS and CCS levels, BECCS sequesters 24–158 GtC by 2100, whereas AR methods sequester around 53 GtC on a global scale, with BECCS having an advantage in the long term. For our specific setup, BECCS has a higher potential in the South American grasslands and southeast Africa, whereas AR methods are more suitable in southeast China. Our results reveal that the efficiency of BECCS to sequester carbon compared to “nature-based solutions” like AR will depend critically on the upscaling of CCS facilities, replacing fossil fuels with bioenergy in the future, the time frame, and the location of tCDR deployment.
... Hydroxide solutions used in high temperature DAC are currently being produced as a by-product of chlorine, but the replacement (make-up) requirement of such materials at scale exceeds the current market supply [68], [27]. Liquid solvent DACCS systems need substantial amounts of water [69], although much less than BECCS systems [70], which could negatively affect SDG 6 (clean water and sanitation). ...
This report provides an overview of the current status, value chains and market positions of carbon capture utilisation and storage (CCUS) technologies in the EU as well as globally. In 2023, the CCUS industry experienced unprecedented growth globally, with all the projects under development summing up to more than 360 Mtpa of CO2 captured. While there are commercially available technologies across all steps of the CCUS chain, work is needed regarding the interconnection of those different steps. The costs of CCUS technologies vary widely depending on the industry, technology, location, plant design and regulatory frameworks in place. According to the review presented here, capture costs lie in the 40-90 EUR/t range for hard-to-abate industries such as cement and the iron and steel sector, while transport costs are within 2-30 EUR/t and storage within 5-35 EUR/t. Taking together Member State and EU funding, the EU was the world leader in public RD&I funding of CCUS technologies in 2022. Within the EU, Germany was the leader, followed by France and Denmark. Global venture capital investment at early stage reached a peak in 2023, with the US attracting most venture capital investment. Lastly, this report shows that new business models are being adopted for the deployment of CCUS projects. While most CCS projects currently in operation follow the full value chain model, issues with this model have resulted more recently in increased traction for partial value chain models, e.g. capture as a service,
transport and storage as a service and self-capture with 3rd party offtake.
... For example, the implementation of negative emission technologies could potentially increase this budget. However, such technologies also have inherent flaws, potentially leading to biophysical, technical and economic risks 56 . Numerous studies have also highlighted that substantially increasing the CO 2 emission budget may be unrealistic, given current constraints and technological limitations 50 . ...
The disparity in environmental impacts across different countries has been widely acknowledged1,2. However, ascertaining the specific responsibility within the complex interactions of economies and consumption groups remains a challenging endeavour3–5. Here, using an expenditure database that includes up to 201 consumption groups across 168 countries, we investigate the distribution of 6 environmental footprint indicators and assess the impact of specific consumption expenditures on planetary boundary transgressions. We show that 31–67% and 51–91% of the planetary boundary breaching responsibility could be attributed to the global top 10% and top 20% of consumers, respectively, from both developed and developing countries. By following an effective mitigation pathway, the global top 20% of consumers could adopt the consumption levels and patterns that have the lowest environmental impacts within their quintile, yielding a reduction of 25–53% in environmental pressure. In this scenario, actions focused solely on the food and services sectors would reduce environmental pressure enough to bring land-system change and biosphere integrity back within their respective planetary boundaries. Our study highlights the critical need to focus on high-expenditure consumers for effectively addressing planetary boundary transgressions.
... Meeting the goal of the Paris Climate Accord to limit global warming to 2 • C requires adopting multiple strategies to rapidly reduce and mitigate carbon emissions. These strategies include an array of negative emission technologies that result in the net removal of greenhouse gases from the atmosphere, including the capture and storage of carbon in vegetation and soil via reforestation, afforestation, and changes in agricultural practices [117,118]. Restoring degraded landscapes will also improve ecological integrity, providing many additional benefits to biodiversity and human well-being [9]. As a result, 56 countries have pledged to restore 168.4 million ha of deforested and degraded land through the Bonn Challenge, which will sequester an estimated 15.7 Gt of CO 2 and generate USD 48.4 billion in economic activity [119]. ...
Climate change is rapidly progressing as the carbon budget balance is broken due to excessive energy and land use. This study was conducted to find and quantify new carbon sinks to implement the carbon neutrality policy prepared by the international community to solve these problems. To reach this goal, an allometric equation of the willow community, which dominates riparian vegetation, was developed and applied to calculate the net primary productivity of the willow community. Furthermore, after the amount of carbon emitted via soil respiration was quantified, the net ecosystem production was calculated by subtracting the amount of soil respiration from the net primary production. In comparisons of the results obtained via this process with those obtained from forest vegetation, the willow community, representative of riparian vegetation, showed a much higher carbon sequestration rate than forest vegetation. Considering these results comprehensively, the willow community could be a new and significant carbon absorption source. In this context, proper river restoration should be realized to contribute to carbon neutrality and secure various ecosystem service functions.
... DAC and BECCS) include capturing CO 2 emissions directly from the atmosphere or manufacturing processes and putting away them underground or using them for several objectives. Smith et al. 65 highlight the significance of combining land-based and technological approaches to attain negative emissions efficiently. ...
... One study estimated that achieving 2°C targets relying primarily on bioenergy with carbon capture and storage (BECCS) would require 380-700 million hectares of land (1.2 to 2. 1 times the area of India). 55 Additionally, urbanization, mining, sand extraction, and the production of plant-derived materials for the bioeconomy are projected to increase xiv Sources of risks are also referred to as 'hazards' in existing conceptual frameworks on environmental risks. ...
The Global Biodiversity Framework’s ‘30x30 targets’ aim to restore and conserve 30% of degraded ecosystems by 2030, as part of broader efforts to halt and reverse nature loss. The macrofinancial risks of conservation-related land use constraints economies remain underexplored, yet increased competition between land uses calls into question potential trade-offs between economic development and ecosystem protection/restoration. This paper first presents a novel conceptual framework articulating the channels by which a transition to implement the 30x30 targets may affect economic and financial stability. A key finding of this framework is that the importance of productive land to primary commodity production, as well as the specific role land plays within the financial system, means that land-related transition policy shocks impose additional and distinct risk transmission channels compared to climate-related policy shocks. Next, the paper uses a simple cluster analysis approach to explore which countries and regions might be most exposed to increased land competition between conservation and economic activities, indicating where macrofinancial risks might be most likely to emerge. Our results suggests that risks are likely to be disproportionately skewed towards low- and middle-income countries, that generally have a higher proportion of lands of conservation importance, a higher exposure to land competition pressures, and a lower adaptability of the economy to pressures on the food system. Our findings contribute to the growing literature on nature-related transition risks and also provide crucial insights for policymakers advancing green transition strategies.
... 2 To achieve the goal of the UNFCC Paris agreement to reduce the rise in the world average temperature far below 2 °C, Carbon sequestration projects are necessitated in every part of the world. 3 Over the decade of 2020, to achieve net-zero carbon targets by 2050, it is predicted that global CO 2 emissions reduced by 7.6% annually4. The least expensive way to minimize this gas is by biological sequestration of carbon in plants. ...
Sacred groves are those forest patches that are connected with the religious and traditional values and beliefs of local people. Plants which are grown near the grove are called sacred plants. Sacred groves include several endemic, endangered and ecologically important plant species. In other words, sacred groves are natural conservation units for biodiversity. Sacred groves and sacred plants are protected and conserved due to the strong religious and mythological beliefs of local people. Their beliefs are as strong as their social traditions. The religious and cultural rites that are performed in the groves give it protection, as well as assisting in keeping the sacred grove in immaculate condition and ensuring the maintenance of its plants. As it is known that the trees are cutting day- by- day and on the other hand Sacred trees which grow near sacred groves are not under threat of cutting due to religious and cultural beliefs. Therefore, Sacred trees or sacred forest a potential role in the sequestration of atmospheric CO2 in the form of biomass. To estimation of Biomass and carbon sequestration in the Sacred tree species have been using a non-destructive method. The main focus of the current article is on estimating the carbon sequestration of sacred tree species in sacred groves found in selected areas Mundra Taluka of Kachchh District. Total 32 sacred groves were recorded from 18 villages which cover approximately 12.77 hectares of land area. Carbon sequestration of 172 individuals of 16 tree species was estimated through the standard method. Ficus benghalensis L. sequestered maximum carbon, i.e., 5.48 tones followed by Azadirachta indica A. Juss. (4.34 tones), Syzigium cumini (L.) Skeels (3.79 tones) While the lowest carbon sequestration was recorded in Pithecellobium dulce (Roxb.) Benth (0961 tones), Prosopsis cineraria (L.) Druce (0.907 tones), Acacia catechu Willd. (0.39 tones) and Tamarindus indica L. (0.173 tones).
... With this approach, the cost of sequestering one ton of carbon would be equal to USD 457 in 2030, falling to USD 100 by 2100 owing to declining renewable energy costs and growing carbon sequestration by mature trees (Caldera and Breyer, 2023). Carbon removal with afforestation is estimated to cost about USD 17-30 per ton in 2100 (Smith et al., 2016). ...
Between 2001 and 2020, the loss of ecosystems worldwide due to land degradation resulted in an economic loss of nearly USD 2 trillion. Restoring degraded lands is essential for mitigating climate change and maintaining biodiversity. Here, we evaluate the potential costs and benefits of restoring degraded lands. We provide unprecedented spatially granular estimates of the carbon removal and broader economic potential of land restoration at a global level and find that restoration of degraded ecosystems such as forests and grasslands can be economically profitable and has considerable carbon sequestration potential, with an average global cost of USD 50 per ton of carbon. The cost of restoring ecosystems degraded between 2001 and 2020 amounts to USD 6.9 trillion. However, each dollar invested is estimated to return USD 2.39 over a 30-year period, and a total of 138 gigatons of carbon would be sequestered.
... The need to understand forest soils and their importance for ecosystem functions like carbon (C) sequestration is becoming more important with the growing threat of climate change [1]. A review of negative emissions technologies suggested that afforestation and reforestation is the most cost-effective approach to mitigating the effects of global warming, although forest preservation may have the most significant potential impact [2]. In many temperate rainforest systems, less than 18% of the world's original primary old-growth forests remain [3]. ...
Forest restoration thinning may accelerate the development of structural complexity toward old-growth conditions faster than a natural forest, yet associated changes in forest carbon (C) are poorly understood. Old-growth forests are characterized by high levels of sequestered C in aboveground biomass and soil C pools, yet active management has well-recognized negative impacts on stored C. Effects of forest restoration thinning on forest C can be determined using longitudinal measurements and modeling based on stand conditions and tree growth. At Ellsworth Creek Preserve in Southwest Washington, forest restoration efforts in a second-growth temperate rainforest have been monitored using permanent plots since 2007. Here, we compare repeat measurements from 2020, modeled forest C, and measurements of O-horizon C pools from 2022 to determine C impacts of silvicultural treatments for old-growth restoration. We found good general agreement between empirical measurements and models of forest C using the Forest Vegetation Simulator (FVS). However, treatment alone was not a strong indicator for C conditions; rather, forest age and age–treatment interactions better predicted soil C responses to restoration treatments. These data may indicate that “light” forest restoration thinning can accelerate old-growth development with minimal effects on soil carbon—a win-win conservation strategy for old-growth forests and the climate.
... Even so, our area estimates likely exceed the global demand for land-based mitigation. U.N. member countries have pledged closer to 1 billion hectares for implementing LBMS (Dooley et al., 2023;IPCC, 2022), and for individual strategies, our area estimates fall toward the upper bound of land needed to mitigate climate change to <2°C by 2100 (IPCC, 2022;Smith et al., 2016). For example, to achieve a climate close to this goal following socioeconomic pathways S1-S5, the IPCC estimates between 150 Mha and 800 Mha needed for energy crops and 600-1500 Mha needed for increased forest cover (IPCC, 2022). ...
Land‐based mitigation strategies (LBMS) are critical to reducing climate change and will require large areas for their implementation. Yet few studies have considered how and where LBMS either compete for land or could be deployed jointly across the Earth's surface. To assess the opportunity costs of scaling up LBMS, we derived high‐resolution estimates of the land suitable for 19 different LBMS, including ecosystem maintenance, ecosystem restoration, carbon‐smart agricultural and forestry management, and converting land to novel states. Each 1 km resolution map was derived using the Earth's current geographic and biophysical features without socioeconomic constraints. By overlaying these maps, we estimated 8.56 billion hectares theoretically suitable for LBMS across the Earth. This includes 5.20 Bha where only one of the studied strategies is suitable, typically the strategy that involves maintaining the current ecosystem and the carbon it stores. The other 3.36 Bha is suitable for more than one LBMS, framing the choices society has among which LBMS to implement. The majority of these regions of overlapping LBMS include strategies that conflict with one another, such as the conflict between better management of existing land cover types and restoration‐based strategies such as reforestation. At the same time, we identified several agricultural management LBMS that were geographically compatible over large areas, including for example, enhanced chemical weathering and improved plantation rotations. Our analysis presents local stakeholders, communities, and governments with the range of LBMS options, and the opportunity costs associated with scaling up any given LBMS to reduce global climate change.
... The removal of CO 2 from the atmosphere is a critical component in mitigating climate change, and in fact most emissions scenarios in integrated assessment models include some form of carbon capture through conservation, restoration, and land management practices (Smith et al 2016a). SOC is the measurable component of soil organic matter (SOM) with estimates of 1500-2400 Pg of carbon stored in the first 1-2 meters of soil globally, more than twice the amount of carbon stored in the atmosphere (Beillouin et al 2022). ...
The need to transition to sustainable agricultural practices while maintaining high food yield and strengthening resilience to climate change cannot be overstated. California farmers have received incentive funding from federal and state agencies to use land management practices that are less impactful to the land and in line with California’s sustainability goals. However, there are no regional monitoring measures to determine whether farming is becoming more sustainable. In this study, we used land cover change analysis and ecosystem services (ES) modeling to understand how farming practices influence environmental benefits on California farmland from 2010 to 2020. We analyzed the tradeoffs between soil erosion control, soil carbon storage, and production of California’s top agricultural commodities, and we compared these changes to changes in land cover in five agricultural regions statewide. We found that the trade-offs in ESs and food production differ depending on the regional context, and that major expansion in almond production and land use changes have had different impacts throughout California. Statewide, soil organic carbon storage increased, soil erosion control increased slightly, and food production boomed for most commodities. Incentive programs that influence farming practices may need to operate at a regional level rather than a statewide level to achieve sustainable outcomes specific to each region.
... However, BECCS is not widely deployed currently, and it is more costly than A/R. Biomass production associated with potential large-scale adoption of BECCS also raises environmental and socio-economic concerns related to land use changes, biodiversity loss, water use, and commodity prices, among others [22][23][24][25][26] . Second-generation energy crops and wood from managed forestry 27 , as well as use of wastes and residues 28 may reduce sustainability issues, although the true potential of sustainable biomass remains uncertain. ...
Carbon dioxide removal (CDR) technologies and international emissions trading are both widely represented in climate change mitigation scenarios, but the interplay among them has not been closely examined. By systematically varying key policy and technology assumptions in a global energy-economic model, we find that CDR and international emissions trading are mutually reinforcing in deep decarbonization scenarios. This occurs because CDR potential is not evenly distributed geographically, allowing trade to unlock this potential, and because trading in a net-zero emissions world requires negative emissions, allowing CDR to enable trade. Since carbon prices change in the opposite direction as the quantity of permits traded and CDR deployed, we find that the total amount spent on emissions trading and the revenue received by CDR producers do not vary strongly with constraints on emissions trading or CDR. However, spending is more efficient and GDP is higher when both CDR and trading are available.
... Several authors have identified reforestation as a carbon mitigation strategy with a high potential capacity for carbon sequestration, albeit with high levels of uncertainty (Bastin et al., 2019;Chazdon & Brancalion, 2019;Griscom et al., 2017). Other authors, however, have pointed to discrepancies and overestimates in the amount of land that is deemed suitable for forest restoration on the basis that it may represent technically unfeasible locations, or is naturally the location of other ecosystem types (and such the proposals are therefore 'afforestation') Smith et al., 2016;Veldman et al., 2019;Veldman et al., 2015). Of particular relevance to the identification and management of risks associated with carbon mitigation projects, many of the locations proposed for forest restoration may be occupied by other ecosystem types such as grasslands and shrublands (Fleiss et al., 2023;Lindenmayer et al., 2012;Van Wilgen & Richardson, 2014;Veldman et al., 2015). ...
... The escalating atmospheric concentration of carbon dioxide (CO 2 ) since the Industrial Revolution poses a critical global concern, primarily due to its profound impact on climate and agriculture. CO 2 levels have risen by approximately 30% since pre-industrial times, primarily due to human activities, such as fossil fuel combustion and deforestation [1,2]. This increase has altered global carbon dynamics, prompting significant concerns about its implications for agricultural production, ecosystem stability, and human livelihoods worldwide. ...
Rising atmospheric CO2 levels, a significant consequence of anthropogenic activities, profoundly impact global agriculture and food security by altering plant physiological processes. Despite extensive research, a comprehensive understanding of the specific effects of elevated CO2 on maize (Zea mays L.)’s primary and secondary metabolism remains elusive. This study investigated the responses of maize seedlings cultivated in open-top chambers (OTCs) under three CO2 concentrations: ambient (380 ppm), elevated (600 ppm), and high (1800 ppm). Key growth parameters, including plant height, leaf area, and aboveground biomass (leaf and stem), were assessed alongside metabolic profiles encompassing nonstructural and structural carbohydrates, syringyl (S) and guaiacyl lignin, the syringyl-to-guaiacyl (S/G)-lignin ratio, photosynthetic pigments, total soluble protein, and malondialdehyde (MDA) levels. The results demonstrated that exposure to 600 ppm CO2 significantly enhanced plant height, leaf area, and aboveground biomass compared to ambient conditions. Concurrently, there were notable increases in the concentrations of primary metabolites. In contrast, exposure to 1800 ppm CO2 severely inhibited these growth parameters and induced reductions in secondary metabolites, such as chlorophyll and soluble proteins, throughout the growth stages. The findings underscore the intricate responses of maize metabolism to varying CO2 levels, highlighting adaptive strategies in primary and secondary metabolism under changing atmospheric conditions. This research contributes to a nuanced understanding of maize’s physiological adaptations to future climate scenarios characterized by elevated CO2, with implications for sustainable agriculture and food security.
... The sustainability risks of BECCS -such as increased land use and conversion, water use and fertilizer use, and their related adverse effects on food security, biodiversity and greenhouse gas emissions -have been relatively well explored and are similar to those of large-scale afforestation/reforestation covered in the section on the potential risks of conventional CDR. 349,385,387,[398][399][400][401][402][403] Large-scale DACCS deployment requires volumes of sorbent bulk materials orders of magnitude larger than are produced today as well as significant energy requirements, on the order of a quarter to a third of today's global energy production. 393,404 Deploying enhanced rock weathering at scale would have a significant mining footprint, and the required rock grinding would have a significant energy and water footprint, with related potential negative impacts on biodiversity, on local water availability and quality, and on air quality. ...
The State of CDR reports are intended to regularly inform researchers, policymakers and practitioners on the state of progress, by systematically collecting and analysing the vast amount of data and developments in many parts of the world.
The second edition continues the assessment of CDR development, expanding geographical coverage and including new topics such as voluntary markets and monitoring, reporting and verification.
Starting with Edition 2, authors of the report have compiled data on a number of Key Indicators of the State of CDR. These indicators showcase the current state of play, direction of travel, and benchmarks for future CDR needs consistent with sustainably limiting temperature increase in line with the Paris Agreement. The data behind these indicators will be freely available via the newly developed State of CDR data portal.
The State of Carbon Dioxide Removal Edition 2 identified a subset of scenarios that can be considered “more sustainable”. Across this group of scenarios, the central range of CDR deployment is 7 to 9 GtCO₂ per year in 2050.
Around 2 GtCO₂ per year of CDR is taking place already. Almost all of this comes from conventional CDR methods. Novel CDR methods contribute 1.3 million tons (0.0013 Gt) of CO₂ removal per year. That is less than 0.1% of total CDR, but novel methods are growing more rapidly than conventional methods.
... The economic feasibility of large-scale biomass-CCS implementation hinges on several factors, including technology costs, market dynamics, policy incentives, and environmental benefits. Biomass-CCS, which involves capturing and storing CO 2 produced during biomass energy generation, can potentially yield negative emissions, a crucial advantage for meeting climate goals [119]. However, the high upfront capital and operational costs for CCS infrastructure, combined with the need for sustainable biomass supply chains, present significant economic challenges [120]. ...
The urgency to mitigate greenhouse gas emissions has catalyzed interest in sustainable biomass production and utilization coupled with carbon capture and storage (CCS). This review explores diverse facets of biomass production, encompassing dedicated energy crops, agricultural residues, and forest residues, along with sustainable production practices and land management strategies. Technological advancements aimed at enhancing biomass yields, including precision agriculture, genetic engineering, and advanced processing technologies, are examined. Thermochemical methods (gasification, pyrolysis) and biochemical methods (anaerobic digestion, fermentation) for biomass conversion are detailed, highlighting their roles in biomass utilization. Integrated biorefineries are emphasized for maximizing biomass efficiency. The review thoroughly covers CCS, including CO2 capture and transport advancements, innovative storage solutions, and challenges in implementation. Bioenergy with carbon capture and storage (BECCS) strategies for achieving negative emissions are discussed, with insights from case studies like the BIO-CAP-UK project and initiatives in New South Wales, Australia. This review provides a comprehensive overview of sustainable biomass pathways and their critical role in CCS, offering insights into current technologies, limitations, and concluding with implications for climate change mitigation strategies.
Achieving a low-carbon future requires a comprehensive approach that combines emission mitigation options from economic activities with the sustainable use of land for numerous needs: food production, energy production, carbon sequestration, nature preservation and broad ecosystem services. Using the MIT Integrated Global System (IGSM) framework we analyze land-use competition in a 1.5°C climate stabilization scenario, in which demand for bioenergy and natural sinks increase along with the need for sustainable farming and food production. We find that to address the numerous trade-offs, effective approaches to nature-based solutions (NBS) and agriculture practices are essential. With proper regulatory policies and radical changes in current practices, global land is sufficient to provide increased consumption of food per capita (without large diet changes) over the century while also utilizing 2.5–3.5 billion hectares (Gha) of land for NBS practices that provide a carbon sink of 3–6 gigatonnes (Gt) of CO2 per year as well as 0.4–0.6 Gha of land for energy production—0.2–0.3 Gha for 50–65 exajoules (EJ) per year of bioenergy and 0.2–0.35 Gha for 300–600 EJ/year of wind and solar power generation. We list the competing uses of land to reflect the trade-offs involved in land use decisions, and note that while there is sufficient land in our scenario, attaining this outcome, capable of delivering a 1.5°C future, requires effective policies and measures at national and global levels that promote efficient land use for food, energy and nature (including carbon sequestration) and ensure long-term commitments by decision makers from governments and industry in order to realize the benefits of climate change mitigation.
Soil carbon sequestration plays a vital role in mitigating climate change and ensuring sustainable agricultural practices. In the Global South, where the majority of the world’s population resides, enhancing soil carbon sequestration is of utmost importance for promoting food security, climate resilience, and environmental sustainability. The roles of microbes and biological matter in enhancing soil carbon sequestration in the Global South are explored in this chapter. The chapter begins by providing an introduction to the significance of soil carbon sequestration and the specific focus on microbial communities and biological matter. Understanding the dynamics of soil carbon sequestration and the factors influencing it forms the foundation for effective strategies. We discuss the current challenges and opportunities faced in the Global South regarding soil carbon sequestration and highlight the urgent need for sustainable solutions. Microbes, such as bacteria and fungi, are key players in carbon cycling and storage. We delve into the intricate interactions between soil microbial communities and plant roots and emphasize their contribution to carbon sequestration. We explore microbial processes involved in organic matter decomposition, nutrient cycling, and the formation of stable soil organic carbon. Highlighting the crucial role of microbial activity in promoting soil health and carbon storage, we discusse strategies for harnessing microbial potential. Moreover, the chapter examines the role of biological matter, such as crop residues and cover crops, in enhancing soil carbon sequestration. Effective management of organic inputs and residues is essential for carbon accumulation. We explore practices like crop residue management, cover cropping, composting, and biochar application that promote carbon sequestration and enhance soil fertility. Drawing from successful case studies, we provide practical insights into the implementation of these strategies and their positive impacts. The chapter addresses barriers related to knowledge gaps, policy frameworks, and economic considerations. We emphasize the importance of integrating sustainable soil management practices into broader agricultural and environmental policies. In conclusion, the book chapter underscores the critical roles of governments, NGOs, private sector, microbes, and biological matter in enhancing soil carbon sequestration in the Global South.
Zdając sobie sprawę ze znaczenia, jakie ma usuwanie dwutlenku węgla dla realizacji globalnych i unijnych celów klimatycznych, Komisja Europejska we wniosku ogłoszonym 30 listopada 2022 r. zaproponowała ramy prawne certyfikacji dobrowolnego usuwania dwutlenku węgla (CDR). Starania Unii Europejskiej o stworzenie systemu certyfikacji CDR są ważną inicjatywą w tym zakresie, ale wiążą się z kluczowymi wyzwaniami, które powinny zostać pokonane w trakcie trwających procesów legislacyjnych. Cel opracowania stanowi ocena treści rzeczonego projektu rozporządzenia z punktu widzenia jego skuteczności jako narzędzia klimatycznego.
Afforestation, reforestation, and revegetation (ARR) projects play a crucial role to combat climate change. In Colombia, ARR projects are important to achieve forest restoration and greenhouse gas emission reduction targets. Our study presents a comprehensive review of 74 ARR projects in Colombia, examining their spatial distribution, characteristics, and restorative interventions. The projects were identified through a review of carbon registry web pages. Data on project timelines, estimated carbon removal, locations, sizes, natural regions, biomes, species approaches, number of planted species, and types of restorative interventions were extracted from project description documents, validation, monitoring and verification reports. Overall, these projects have treated an area of 314,374 ha, with an estimated removal of 101,553,801 tons of CO2 during the crediting period. The analysis revealed that the Andean, Caribbean, and Orinoco regions had the highest number of ARR projects, while the Pacific and Amazon regions had fewer initiatives. Mixed species plantings were the most common approach, followed by exotic and native species. Afforestation was the most frequent forestry intervention, followed by revegetation. However, the study also identifies concerning trends, such as the widespread use of invasive species and large number of afforestation projects in naturally non-forest ecosystems. These findings offer critical insights for the governance of ARR projects in Colombia, emphasizing the need to assure quality in carbon sequestration efforts while enhancing ecological and social benefits. Finally, the study supports Colombia’s broader goals of biodiversity restoration and climate resilience.
Limiting global warming requires the effective implementation of energy mitigation measures by individual countries. However, the consequences of the timing of these efforts on the technical feasibility of adhering to cumulative carbon budgets—which determines future global warming—are underexplored. Moreover, existing national studies on carbon budgets either overlook integrated sectoral interactions, path dependencies, or comprehensive demand-side strategies. To address this, we analyse Ireland’s mitigation pathways under equal per-capita carbon budgets using an energy systems optimisation model. Our findings reveal that delayed mitigation brings forward the need for a net-zero target by five years, risks carbon lock-in and stranded assets, increase reliance on carbon dioxide removal technologies and leads to higher long-term mitigation costs. To keep the Paris Agreement targets, countries must set and meet accelerated mid-term mitigation goals and address energy demand.
Modern agriculture faces the challenge of meeting global food demand sustainably. Soil nutrient management is crucial, but traditional methods using agrochemicals pose environmental and economic issues. Biopolymer nanoparticles offer a promising alternative, sourced from natural materials with unique properties for precise soil nutrient delivery. They have the potential to enhance crop productivity while minimizing environmental impact. This chapter delves into biopolymer nanoparticles, examining their synthesis, characteristics, and applications, particularly in addressing soil nutrient management challenges. By exploring this topic, the study highlights the transformative role of biopolymer nanoparticles in revolutionizing agriculture towards sustainability.
We review how the international modelling community, encompassing integrated assessment models, global and regional Earth system and climate models, and impact models, has worked together over the past few decades to advance understanding of Earth system change and its impacts on society and the environment and thereby support international climate policy. We go on to recommend a number of priority research areas for the coming decade, a timescale that encompasses a number of newly starting international modelling activities, as well as the IPCC Seventh Assessment Report (AR7) and the second UNFCCC Global Stocktake. Progress in these priority areas will significantly advance our understanding of Earth system change and its impacts, increasing the quality and utility of science support to climate policy.
We emphasize the need for continued improvement in our understanding of, and ability to simulate, the coupled Earth system and the impacts of Earth system change. There is an urgent need to investigate plausible pathways and emission scenarios that realize the Paris climate targets – for example, pathways that overshoot 1.5 or 2 °C global warming, before returning to these levels at some later date. Earth system models need to be capable of thoroughly assessing such warming overshoots – in particular, the efficacy of mitigation measures, such as negative CO2 emissions, in reducing atmospheric CO2 and driving global cooling. An improved assessment of the long-term consequences of stabilizing climate at 1.5 or 2 °C above pre-industrial temperatures is also required. We recommend Earth system models run overshoot scenarios in CO2-emission mode to more fully represent coupled climate–carbon-cycle feedbacks and, wherever possible, interactively simulate other key Earth system phenomena at risk of rapid change during overshoot. Regional downscaling and impact models should use forcing data from these simulations, so impact and regional climate projections cover a more complete range of potential responses to a warming overshoot. An accurate simulation of the observed, historical record remains a fundamental requirement of models, as does accurate simulation of key metrics, such as the effective climate sensitivity and the transient climate response to cumulative carbon emissions. For adaptation, a key demand is improved guidance on potential changes in climate extremes and the modes of variability these extremes develop within. Such improvements will most likely be realized through a combination of increased model resolution, improvement of key model parameterizations, and enhanced representation of important Earth system processes, combined with targeted use of new artificial intelligence (AI) and machine learning (ML) techniques. We propose a deeper collaboration across such efforts over the coming decade.
With respect to sampling future uncertainty, increased collaboration between approaches that emphasize large model ensembles and those focussed on statistical emulation is required. We recommend an increased focus on high-impact–low-likelihood (HILL) outcomes – in particular, the risk and consequences of exceeding critical tipping points during a warming overshoot and the potential impacts arising from this. For a comprehensive assessment of the impacts of Earth system change, including impacts arising directly as a result of climate mitigation actions, it is important that spatially detailed, disaggregated information used to generate future scenarios in integrated assessment models be available for use in impact models. Conversely, there is a need to develop methods that enable potential societal responses to projected Earth system change to be incorporated into scenario development.
The new models, simulations, data, and scientific advances proposed in this article will not be possible without long-term development and maintenance of a robust, globally connected infrastructure ecosystem. This system must be easily accessible and useable by modelling communities across the world, allowing the global research community to be fully engaged in developing and delivering new scientific knowledge to support international climate policy.
The accelerating impacts of climate change, driven by rising carbon dioxide (CO2) emissions, underscore the need for effective mitigation strategies, particularly in Carbon Capture and Storage (CCS). This urgency is further catalyzed by the Inflation Reduction Act of 2022, which provides incentives primarily for the Geological Storage of CO2 (GSC) and carbon utilization. However, to meet the impending 2050 carbon emissions deadline, all available emerging technologies need to be deployed. This paper aims to evaluate and integrate established and emerging technologies for CO2 storage to increase storage capacity, safety, and scalability in the global effort to combat climate change. The study provides a comprehensive review of existing GSC methods, such as deep saline aquifers and depleted oil and gas reservoirs, and explores emerging technologies, including the repurposing of unconventional reservoirs, modifying thermodynamic conditions, nanofluid-enhanced CO2 storage, and CO2-plume geothermal CO2 storage. The approach focuses on each method, highlighting gaps, opportunities, pros and cons, and how these technologies can be integrated. Key findings indicate that most of these technologies are in early-stage development; thus, full-scale research, development, or demonstration projects are required to accelerate deployment. Additionally, incentives such as funding, inclusion in the Inflation Reduction Act, and technical expertise are essential for widespread application. This effort can be further supported by offering carbon credits for verifiable CCS projects, spurring additional technological investment. Such integration can significantly improve storage capacity, operational efficiency, and cost-effectiveness, making GSC a more viable solution for achieving global climate targets.
Soil plays a central role in the global carbon (C) cycle and the fight against climate change as it contains the largest existing organic C stock on earth. Natural processes exacerbated by climate change and unsustainable agricultural soil management practices are contributing to the steady decrease in organic C stocks in farmland. Carbon farming practices, underpinned by various incentives, can be used to maintain and increase C stocks in agricultural soils. Carbon credit mechanisms, that is, tradable credits each corresponding to one tonne of CO 2 eq, are one such incentive. Carbon credits are issued upon the demonstration of increased soil C stocks over time through the application of C accounting methodologies for each agroecosystem and farming practice. This study presents a detailed and critical analysis of carbon credit methodologies, focusing on agricultural soil C in temperate zones, by comparing the European Commission proposal for a regulation on carbon removals with relevant certification frameworks implemented in extra‐European Union industrialized countries (Australia, Alberta in Canada, United States). Based on this, we recommend strengthening the European Commission proposal by (i) expanding the list of eligible agricultural practices, (ii) setting a minimum maintenance time frame for each agricultural practice and incentivizing longer duration, (iii) setting the Good Agricultural and Environmental Conditions of the European Common Agricultural Policy (CAP) as a regulatory baseline, (iv) beyond the regulatory baseline, defining a farm level baseline in terms of carbon farming practices applied that can be monitored through the Integrated Administration and Control System of the CAP, (v) clarifying the interaction between the European Commission proposal of regulation and the CAP, the Soil Monitoring Law, and Land Use/Cover Area Frame Survey inventory, (vi) retaining a portion of unsold carbon credits as a buffer against the risk of reversal and (vii) applying a default discount to account for leakage risk if yield reductions are observed. We propose these recommendations to guarantee effective environmental protection, technical and bureaucratic feasibility as well as economic affordability for farmers.
As the global need for renewable energy grows, bioenergy crops have emerged as a promising solution for sustainable energy production. Euphorbia Tirucalli (ET), a resilient and drought-tolerant plant, has shown remarkable potential as a bioenergy source due to its ability to thrive in arid regions and produce significant biomass. Beyond its bioenergy capabilities, ET is also capable of capturing atmospheric carbon, making it a viable candidate for carbon-negative energy systems. By genetically enhancing ET, we can optimize its growth rate, carbon sequestration capacity, and biofuel production potential, making it a more efficient crop for large-scale deployment. This paper explores various genetic modifications aimed at improving ET’s biomass yield, nitrogen fixation capabilities, and integration with advanced energy systems, such as microbial fuel cells and artificial photosynthesis. These innovations could lead to a new generation of bioenergy crops capable of addressing both renewable energy demands and the urgent need to mitigate climate change through carbon capture and sequestration.
Keywords: Euphorbia Tirucalli, bioenergy, carbon sequestration, genetically modified crops, nitrogen fixation, microbial fuel cells, artificial photosynthesis, lignin modification, biofuel, climate change, sustainable energy, carbon-negative, biomass production. 49 pages.
Climate change poses significant challenges to the health and sustainability of global forests, impacting their structure, function, and biodiversity. This chapter offers a comprehensive insight into the intricate relationship between climate change and forest ecosystems from a biological standpoint. Climate change, encompassing alterations in temperature, precipitation patterns, and extreme weather events, may significantly disrupt forest ecosystems, leading to shifts in species distributions, changes in phenology, and increased susceptibility to pests and diseases. Forests play a crucial role in climate regulation by sequestering carbon dioxide from the atmosphere through photosynthesis. Nonetheless, the capacity of forests to function as carbon sinks is undermined by climate change-induced factors such as increased tree mortality and diminished growth rates. Understanding the science behind the interactions between climate change and forests is essential for developing effective strategies to conserve and sustainably manage forest ecosystems under the influence of global climate change. Exploring the complex interplay between climate change and forests is needed for international, national, and local collaborative action to safeguard forest ecosystems and mitigate the impacts of climate change. This chapter serves as an invaluable resource for researchers, policymakers, forest managers, and conservation practitioners striving to address the challenges presented by climate change and cultivate resilience in forest ecosystems to benefit future generations.
Despite the increasing relevance of temperature overshoot and the rather ambitious country pledges on Afforestation/Reforestation globally, the mitigation potential and the Earth system responses to large-scale non-idealized Afforestation/Reforestation patterns under a high overshoot scenario remain elusive. Here, we develop an ambitious Afforestation/Reforestation scenario by harnessing 1259 Integrated Assessment Model scenarios, restoration potential maps, and biodiversity constraints, reaching 595 Mha by 2060 and 935 Mha by 2100. We then force the Max Planck Institute’s Earth System Model with this scenario which yields a reduction of peak temperature by 0.08 oC, end-of-century temperature by 0.2 oC, and overshoot duration by 13 years. Afforestation/Reforestation in the range of country pledges globally could thus constitute a useful mitigation tool in overshoot scenarios in addition to fossil fuel emission reductions, but socio-ecological implications need to be scrutinized to avoid severe side effects.
Introduction
For limiting global warming to well below 2°C rapid and stringent GHG emissions reductions are required. In addition, we also need to actively remove CO 2 from the atmosphere via carbon dioxide removal (CDR). This will require advances in policymaking and governance to incentivise, coordinate and regulate CDR, including strict monitoring to ensure durable, additional removals that do not compete with emission reduction efforts. While it is critical to learn from the existing evidence on CDR policy and governance, there is no overview of this dispersed body of literature right now. IPCC and other science assessments have therefore treated the subject very selectively. This work addresses this lack of overview by systematically mapping the literature assessing policy and governance dimensions of CDR.
Methods
Systematic mapping provides a comprehensive view of a research field by analysing the state of evidence, i.e. how much research is available at any point in time on which topics and geographies studied by whom, when and where. We use an AI-enhanced approach to systematic mapping, trimming down an initial set of about 30,000 documents on CDR to a set of 876 that deal with governance and policy issues.
Results
Our findings show sharply growing attention to CDR policies and governance issues over time, but with limited coverage of the Global South. Long established conventional CDR methods such as afforestation dominate the literatureparticularly in ex-post studies -with little coverage of many novel CDR methods, such as biochar or direct air carbon capture and storage. We observe a shift from an initial discussion on CDR in international agreements towards the planning and implementation phase of national and sub-national policies.
Discussion
Our map can help to inform upcoming science assessments with critical information around CDR policies and governance and might serve as a starting point for generating a rigorous knowledge base on the topic in the future.
Achieving a net zero emissions economy requires a nuanced understanding of how policy, politics, and governance intersect and drive progress. This chapter explores into the interconnected relationship among these dimensions in advancing the goal of net zero emissions. Firstly, it examines the role of policy frameworks in incentivizing decarbonization across various sectors, with a focus on integrating national and international policies for global cooperation. Secondly, it explores the political dynamics influencing the adoption and longevity of net zero policies, stressing the importance of political will and stakeholder collaboration. Lastly, it analyzes governance structures crucial for effective decision-making, emphasizing inclusivity and transparency. Through this interdisciplinary analysis, the study underscores the need for an integrated approach to policy, politics, and governance to realize a sustainable, net zero emissions future.
While Carbon Dioxide Removal (CDR) solutions are considered essential to meet Paris Agreement objectives and curb climate change, their maturity and current ability to operate at scale are highly debated. The rapid development, deployment, and diffusion of such methods will likely require the coordination of science, technology, policy, and societal support. This article proposes a bibliometric approach to quantify the public use of early-stage research in CDR. Specifically, we employ generalized linear models to estimate the likelihood that scientific advances in eight different carbon removal solutions may induce (i) further production of scientific knowledge, (ii) technological innovation, and (iii) policy and media discussion. Our main result is that research in CDR is of significant social value. CDR research generates significant, positive, yet heterogeneous spillovers within science and from science to technology, policy, and media. In particular, advances in Direct Air Capture spur further research and tend to result in patentable technologies, while Blue Carbon and Bio-energy with Carbon Capture and Storage appear to gain relative momentum in the policy and public debate. Moreover, scientific production and collaborations cluster geographically by type of CDR, potentially affecting long-term carbon removal strategies. Overall, our results suggest the existence of coordination gaps between science, technology, policy, and public support.
Although there are many studies on CO2 adsorption via PEI‐modified carbon particles, metal–organic frameworks, zeolitic imidazolate frameworks, and silica‐based porous structures, only a limited number of studies on solely cross‐linked PEI‐based structures. Here, the CO2 adsorption capacities of PEI‐based microgels and cryogels were investigated. The effects of various parameters influencing the CO2 adsorption capacity of PEI‐based structures, for example, crosslinker types, PEI types (branched [bPEI] or linear [lPEI]), adsorbent types (microgel or cryogel), chemical‐modification including their complexes were examined. NaOH‐treated glycerol diglycidyl ether (GDE) crosslinked lPEI microgels exhibited higher CO2 adsorption capacity among other microgels with 0.094 ± 0.006 mmol CO2/g at 900 mm Hg, 25°C with 2‐ and 7.5‐fold increase upon pentaethylenehexamine (PEHA) modification and Ba(II) metal ion complexing, respectively. The CO2 adsorption capacity of bPEI and lPEI‐based cryogels were compared and found that lPEI‐GDE cryogels had higher adsorption capacity than bPEI‐GDE cryogels with 0.188 ± 0.01 mmol CO2/g at 900 mm Hg and 25°C. The reuse studies revealed that NaOH‐treated GDE crosslinked bPEI and lPEI microgels and cryogels showed promising potential, for example, after 10‐times repeated use >50% CO2 adsorption capacity was retained. The results affirmed that PEI‐based microgels and cryogels are encouraging materials for CO2 capture and reuse applications.
This study investigates the environmental and economic implications of Carbon Dioxide Capture and Storage (CCS) in Kenya's coastal region, focusing on its potential as a climate mitigation strategy. CCS technology involves capturing CO2 emissions from industrial sources and storing them underground to prevent their release into the atmosphere. The research adopted a descriptive approach, gathering data from 120 respondents, including government officials, industry experts, and community leaders, through questionnaires and interviews. Findings indicate that while there is moderate to high awareness of CCS, perceptions vary, with concerns about high costs, technical challenges, and environmental risks. The study highlights the potential for CCS to reduce CO2 emissions significantly and attract investments, but also identifies barriers such as the need for robust regulatory frameworks and the high costs of implementation. Environmental risks, such as CO2 leakage, and the absence of specific CCS policies in Kenya pose significant challenges. Recommendations include developing a comprehensive policy framework, enhancing public awareness, fostering public-private partnerships, conducting rigorous environmental impact assessments, and ensuring community engagement in CCS planning. The study underscores the importance of addressing these challenges to effectively integrate CCS into Kenya's climate strategy.
Carbon Dioxide Removals (CDR) and Carbon Capture and Storage (CCS) have received a lot of attention as a tool to mitigate climate change and reach climate neutrality. Bioenergy with Carbon Capture and Storage (BECCS) is seen as one of the more promising CDRs, and from 2026, the Danish utility Ørsted is establishing the first BECCS plants in Denmark. We present a case study of BECCS by installing CCS at a biomass‐fired CHP plant and the aim is to quantify the CDR potential and carbon dynamics of the BECCS system. Moreover, the study aims to quantify the emissions related to capturing and store CO2. The GHG emissions from CCS including heat, electricity, transport and storage are approximately 100 kgCO2/t stored CO2 and the carbon payback time of the BECCS system is 3–4 years relative to leaving the wood in the forest or at processing industries. The main driver of the payback time is the additional use of biomass to operate CCS which shifts the timing of CO2 emissions more towards the present. The additional biomass use also increases supply chain emissions, and on top of that, only 90% of the direct CO2 emissions from the CHP plant are captured. The study illustrates the importance of temporal scope in assessing the CDR potential of BECCS. With continuous use of biomass, GHG emissions are 207 kgCO2/t stored CO2 in year 1 and −742 kgCO2/t stored CO2 in year 99. This study reveals inconsistencies in the assessment of the CDR potential of BECCS in the literature. There is a considerable need for further research within this field to assess how BECCS can contribute to mitigating climate change and on the appropriate scale of BECCS deployment.
Recent studies show that current trends in yield improvement will not be su cientto meet projected global food demand in 2050, and suggest that a further expansion of agricultural area will be required. However, agriculture is the main driver of losses of biodiversity and a major contributor to climate change and pollution, and so further expansion is undesirable. The usual proposed alternative-intensification with increased resource use-also has negative effects. It is therefore imperative to find ways to achieve global food security without expanding crop or pastureland and without increasing greenhouse gas emissions. Some authors have emphasized a role for sustainable intensification in closing global 'yield gaps' between the currently realized and potentially achievable yields. However, in this paper we use a transparent, data-driven model, to show that even if yield gaps are closed, the projected demand will drive further agricultural expansion. There are, however, options for reduction on the demand side that are rarely considered. In the second part of this paper we quantify the potential for demand-side mitigation options, and show that improved diets and decreases in food waste are essential to deliver emissions reductions, and to provide global food security in 2050.
The Emissions Gap Report 2013 from the United Nations Environment Programme restates the claim that changing to no-till practices in agriculture, as an alternative to conventional tillage, causes an accumulation of organic carbon in soil, thus mitigating climate change through carbon sequestration. But these claims ignore a large body of experimental evidence showing that the quantity of additional organic carbon in soil under no-till is relatively small: in large part apparent increases result from an altered depth distribution. The larger concentration near the surface in no-till is generally beneficial for soil properties that often, though not always, translate into improved crop growth. In many regions where no-till is practised it is common for soil to be cultivated conventionally every few years for a range of agronomic reasons, so any soil carbon benefit is then lost. We argue that no-till is beneficial for soil quality and adaptation of agriculture to climate change, but its role in mitigation is widely overstated.
Fossil fuel power generation and other industrial emissions of carbon dioxide are a threat to global climate(1), yet many economies will remain reliant on these technologies for several decades(2). Carbon dioxide capture and storage (CCS) in deep geological formations provides an effective option to remove these emissions from the climate system(3). In many regions storage reservoirs are located offshore(4,5), over a kilometre or more below societally important shelf seas(6). Therefore, concerns about the possibility of leakage(7,8) and potential environmental impacts, along with economics, have contributed to delaying development of operational CCS. Here we investigate the detectability and environmental impact of leakage from a controlled sub-seabed release of CO2. We show that the biological impact and footprint of this small leak analogue (<1 tonne CO2 d(-1)) is confined to a few tens of metres. Migration of CO2 through the shallow seabed is influenced by near-surface sediment structure, and by dissolution and re-precipitation of calcium carbonate naturally present in sediments. Results reported here advance the understanding of environmental sensitivity to leakage and identify appropriate monitoring strategies for full-scale carbon storage operations.
We assess the quantitative potential for future land management to help rebalance the global carbon cycle by actively removing carbon dioxide (CO 2) from the atmosphere with simultaneous bio-energy offsets of CO 2 emissions, whilst meeting global food demand, preserving natural ecosystems and minimising CO 2 emissions from land use change. Four alternative future scenarios are considered out to 2050 with different combinations of high or low technology food production and high or low meat diets. Natural ecosystems are protected except when additional land is necessary to fulfil the dietary demands of the global population. Dedicated bio-energy crops can only be grown on land that is already under management but is no longer needed for food production. We find that there is only room for dedicated bio-energy crops if there is a marked increase in the efficiency of food production (sustained annual yield growth of 1%, shifts towards more efficient animals like pigs and poultry, and increased recycling of wastes and residues). If there is also a return to lower meat diets, biomass energy with carbon storage (BECS) as CO 2 and biochar could remove up to 5.2 Pg C per year in 2050 and lower atmospheric CO 2 in 2050 by 25 ppm. With the current trend to higher meat diets there is only room for limited expansion of bio-energy crops after 2035 and instead BECS must be based largely on biomass residues, removing up to 3.6 Pg C per year in 2050 and lowering atmospheric CO 2 in 2050 by 13 ppm. A high-meat, low-efficiency future would be a catastrophe for natural ecosystems (and thus for the humans that depend on their services) with around 9.3 Gha under cultivation in 2050 and a net increase in atmospheric CO 2 in 2050 by 55 ppm due to land use changes. We conclude that future improvements in agricultural efficiency, especially in the livestock sector, could make a decisive contribution to tackling climate change, but this would be maximised if the global trend towards more meat intensive diets can be reversed.
Bioenergy with Carbon Capture and Storage (BECCS) is a key component of mitigation strategies in future socio-economic scenarios that aim to keep mean global temperature rise below 2 "∘ C above pre-industrial, which would require net negative carbon emissions in the end of the 21st century. Because of the additional need for land, developing sustainable low-carbon scenarios requires careful consideration of the land-use implications of deploying large-scale BECCS. We evaluated the feasibility of the large-scale BECCS in RCP2.6, which is a scenario with net negative emissions aiming to keep the 2 "∘ C temperature target, with a top-down analysis of required yields and a bottom-up evaluation of BECCS potential using a process-based global crop model. Land-use change carbon emissions related to the land expansion were examined using a global terrestrial biogeochemical cycle model. Our analysis reveals that first-generation bioenergy crops would not meet the required BECCS of the RCP2.6 scenario even with a high fertilizer and irrigation application. Using second-generation bioenergy crops can marginally fulfill the required BECCS only if a technology of full post-process combustion CO 2 capture is deployed with a high fertilizer application in the crop production. If such an assumed technological improvement does not occur in the future, more than doubling the area for bioenergy production for BECCS around 2050 assumed in RCP2.6 would be required, however, such scenarios implicitly induce large-scale land-use changes that would cancel half of the assumed CO 2 sequestration by BECCS. Otherwise a conflict of land-use with food production is inevitable.
The land-use sector can contribute to climate change mitigation not only by reducing greenhouse gas (GHG) emissions, but also by increasing carbon uptake from the atmosphere and thereby creating negative CO2 emissions. In this paper, we investigate two land-based climate change mitigation strategies for carbon removal: (1) afforestation and (2) bioenergy in combination with carbon capture and storage technology (bioenergy CCS). In our approach, a global tax on GHG emissions aimed at ambitious climate change mitigation incentivizes land-based mitigation by penalizing positive and rewarding negative CO2 emissions from the land-use system. We analyze afforestation and bioenergy CCS as standalone and combined mitigation strategies. We find that afforestation is a cost-efficient strategy for carbon removal at relatively low carbon prices, while bioenergy CCS becomes competitive only at higher prices. According to our results, cumulative carbon removal due to afforestation and bioenergy CCS is similar at the
Bioenergy deployment offers significant potential for climate change mitigation, but also carries considerable risks. In this review, we bring together perspectives of various communities involved in the research and regulation of bioenergy deployment in the context of climate change mitigation: Land-use and energy experts, land-use and integrated assessment modelers, human geographers, ecosystem researchers, climate scientists and two different strands of life-cycle assessment experts. We summarize technological options, outline the state-of-the-art knowledge on various climate effects, provide an update on estimates of technical resource potential and comprehensively identify sustainability effects. Cellulosic feedstocks, increased end-use efficiency, improved land carbon-stock management and residue use, and, when fully developed, BECCS appear as the most promising options, depending on development costs, implementation, learning, and risk management. Combined heat and power, efficient biomass cookstoves and small-scale power generation for rural areas can help to promote energy access and sustainable development, along with reduced emissions. We estimate the sustainable technical potential as up to 100 EJ: high agreement; 100–300 EJ: medium agreement; above 300 EJ: low agreement. Stabilization scenarios indicate that bioenergy may supply from 10 to 245 EJ yr−1 to global primary energy supply by 2050. Models indicate that, if technological and governance preconditions are met, large-scale deployment (>200 EJ), together with BECCS, could help to keep global warming below 2° degrees of preindustrial levels; but such high deployment of land-intensive bioenergy feedstocks could also lead to detrimental climate effects, negatively impact ecosystems, biodiversity and livelihoods. The integration of bioenergy systems into agriculture and forest landscapes can improve land and water use efficiency and help address concerns about environmental impacts. We conclude that the high variability in pathways, uncertainties in technological development and ambiguity in political decision render forecasts on deployment levels and climate effects very difficult. However, uncertainty about projections should not preclude pursuing beneficial bioenergy options.
Land-use changes through forestry and other activities alter not just carbon storage, but biophysical properties, including albedo, surface roughness, and canopy conductance, all of which affect temperature. This study assessed the biophysical forcings and climatic impact of vegetation replacement across North America by comparing satellite-derived albedo, land surface temperature (LST), and evapotranspiration (ET) between adjacent vegetation types. We calculated radiative forcings (RF) for potential local conversions from croplands (CRO) or grasslands (GRA) to evergreen needleleaf (ENF) or deciduous broadleaf (DBF) forests. Forests generally had lower albedo than adjacent grasslands or croplands, particularly in locations with snow. They also had warmer nighttime LST, cooler daily and daytime LST in warm seasons, and smaller daily LST ranges. Darker forest surfaces induced positive RFs, dampening the cooling effect of carbon sequestration. The mean (6SD) albedo-induced RFs for each land conversion were equivalent to carbon emissions of 2.2 6 0.7 kg C/m 2 (GRA-ENF), 2.0 6 0.6 kg C/m 2 (CRO-ENF), 0.90 6 0.50 kg C/m 2 (CRO-DBF), and 0.73 6 0.22 kg C/m 2 (GRA-DBF), suggesting that, given the same carbon sequestration potential, a larger net cooling (integrated globally) is expected for planting DBF than ENF. Both changes in LST and ET induce longwave RFs that sometimes had values comparable to or even larger than albedo-induced shortwave RFs. Sensible heat flux, on average, increased when replacing CRO with ENF, but decreased for conversions to DBF, suggesting that DBF tends to cool near-surface air locally while ENF tends to warm it. This local temperature effect showed some seasonal variation and spatial dependence, but did not differ strongly by latitude. Overall, our results show that a carbon-centric accounting is, in many cases, insufficient for climate mitigation policies. Where afforestation or reforestation occurs, however, deciduous broadleaf trees are likely to produce stronger cooling benefits than evergreen needleleaf trees provide.
The political will to reduce global GHG emissions has largely contributed to increased global biofuel production and trade. The expanding cultivation of energy crops may drive changes in the terrestrial ecosystems such as land cover and biodiversity loss. When biomass replaces fossil energy carriers, sustainability criteria are there-fore crucial to avoid adverse impacts and ensure a net positive GHG balance. The European Union has set man-datory sustainability criteria for liquid biofuels in its Renewable Energy Directive (RED) 2009/28/EC to ensure net positive impacts of its biofuel policy. The adoption of sustainability criteria in other world regions and their extension to solid and gaseous biomass in the EU is ongoing. This paper examines the effect of the EU RED sus-tainability criteria on the availability of biomass resources at global and regional scale. It quantifies the relevance of sustainability criteria in biomass resource assessments taking into account the criteria's spatial distribution. This assessment does not include agricultural and forestry residues and aquatic biomass. Previously unknown interrelations between sustainability criteria are examined and described for ten world regions. The analysis con-cludes that roughly 10% (98.5 EJ) of the total theoretical potential of 977.2 EJ occurs in areas free of sustainability concerns.
This study explores a situation of staged accession to a global climate policy regime from the current situation of regionally fragmented and moderate climate action. The analysis is based on scenarios in which a front runner coalition – the EU or the EU and China – embarks on immediate ambitious climate action while the rest of the world makes a transition to a global climate regime between 2030 and 2050. We assume that the ensuing regime involves strong mitigation efforts but does not require late joiners to compensate for their initially higher emissions. Thus, climate targets are relaxed, and although staged accession can achieve significant reductions of global warming, the resulting climate outcome is unlikely to be consistent with the goal of limiting global warming to 2 degrees. The addition of China to the front runner coalition can reduce pre-2050 excess emissions by 20–30%, increasing the likelihood of staying below 2 degrees. Not accounting for potential co-benefits, the cost of front runner action is found to be lower for the EU than for China. Regions that delay their accession to the climate regime face a trade-off between reduced short term costs and higher transitional requirements due to larger carbon lock-ins and more rapidly increasing carbon prices during the accession period.
This paper provides an overview of the AMPERE modeling comparison project with focus on the implications of near-term policies for the costs and attainability of long-term climate objectives. Nine modeling teams participated in the project to explore the consequences of global emissions following the proposed policy stringency of the national pledges from the Copenhagen Accord and Cancún Agreements to 2030. Specific features compared to earlier assessments are the explicit consideration of near-term 2030 emission targets as well as the systematic sensitivity analysis for the availability and potential of mitigation technologies. Our estimates show that a 2030 mitigation effort comparable to the pledges would result in a further “lock-in” of the energy system into fossil fuels and thus impede the required energy transformation to reach low greenhouse-gas stabilization levels (450 ppm CO2e). Major implications include significant increases in mitigation costs, increased risk that low stabilization targets become unattainable, and reduced chances of staying below the proposed temperature change target of 2 °C in case of overshoot. With respect to technologies, we find that following the pledge pathways to 2030 would narrow policy choices, and increases the risks that some currently optional technologies, such as carbon capture and storage (CCS) or the large-scale deployment of bioenergy, will become “a must” by 2030.
While the international community aims to limit global warming to below 2 ° C to prevent dangerous climate change, little progress has been made towards a global climate agreement to implement the emissions reductions required to reach this target. We use an integrated energy–economy–climate modeling system to examine how a further delay of cooperative action and technology availability affect climate mitigation challenges. With comprehensive emissions reductions starting after 2015 and full technology availability we estimate that maximum 21st century warming may still be limited below 2 ° C with a likely probability and at moderate economic impacts. Achievable temperature targets rise by up to ~0.4 ° C if the implementation of comprehensive climate policies is delayed by another 15 years, chiefly because of transitional economic impacts. If carbon capture and storage (CCS) is unavailable, the lower limit of achievable targets rises by up to ~0.3 ° C. Our results show that progress in international climate negotiations within this decade is imperative to keep the 2 ° C target within reach.
This paper provides a novel assessment of the role of direct air capture of CO2 from ambient air (DAC) on the feasibility of achieving stringent climate stabilization. We use the WITCH energy-economy-climate model to investigate the long term prospects of DAC, implementing a technological specification based on recent estimates by the American Physical Society (APS 2011). Assuming global cooperation on a stringent climate policy we find that: (1) DAC is deployed only late in century, after other low carbon options, though at a very significant scale; (2) DAC has an impact on the marginal and total abatement costs (reducing them) and on the timing of mitigation (postponing it); (3) DAC also allows for a prolonged use of oil, with a positive welfare impact for energy exporting countries. Finally, we assess the role of DAC in a less than ideal climate policy by exploring its potential for engaging energy exporting countries in climate mitigation activities by means of a “clean oil” market in which oil exporters can sell oil decarbonized via DAC.
Despite 20 years of effort to curb emissions, greenhouse gas (GHG) emissions grew faster during the 2000s than in the 1990s, which presents a major challenge for meeting the international goal of limiting warming to <2 °C relative to the preindustrial era. Most recent scenarios from integrated assessment models require large-scale deployment of negative emissions technologies (NETs) to reach the 2 °C target. A recent analysis of NETs, including direct air capture, enhanced weathering, bioenergy with carbon capture and storage and afforestation/deforestation, showed that all NETs have significant limits to implementation, including economic cost, energy requirements, land use, and water use. In this paper, I assess the potential for negative emissions from soil carbon sequestration and biochar addition to land, and also the potential global impacts on land use, water, nutrients, albedo, energy and cost. Results indicate that soil carbon sequestration and biochar have useful negative emission potential (each 0.7 GtCeq. yr−1) and that they potentially have lower impact on land, water use, nutrients, albedo, energy requirement and cost, so have fewer disadvantages than many NETs. Limitations of soil carbon sequestration as a NET centre around issues of sink saturation and reversibility. Biochar could be implemented in combination with bioenergy with carbon capture and storage. Current integrated assessment models do not represent soil carbon sequestration or biochar. Given the negative emission potential of SCS and biochar and their potential advantages compared to other NETs, efforts should be made to include these options within IAMs, so that their potential can be explored further in comparison with other NETs for climate stabilization.
Climate changes will affect food production in a number of ways. Crop yields, aquatic populations and forest productivity will decline, invasive insect and plant species will proliferate and desertification, soil salinization and water stress will increase. Each of these impacts will decrease food and nutrition security, primarily by reducing access to and availability of food, and also by increasing the risk of infectious disease. Although increased biofuel demand has the potential to increase incomes among producers, it can also negatively affect food and nutrition security. Land used for cultivating food crops may be diverted to biofuel production, creating food shortages and raising prices. Accelerations in unregulated or poorly regulated foreign direct investment, deforestation and unsustainable use of chemical fertilizers may also result. Biofuel production may reduce women's control of resources, which may in turn reduce the quality of household diets. Each of these effects increases risk of poor food and nutrition security, either through decreased physical availability of food, decreased purchasing power, or increased risk of disease. The Impact of Climate Change and Bioenergy on Nutrition articulates the links between current environmental issues and food and nutrition security. It provides a unique collection of nutrition statistics, climate change projections, biofuel scenarios and food security information under one cover which will be of interest to policymakers, academia, agronomists, food and nutrition security planners, programme implementers, health workers and all those concerned about the current challenges of climate change, energy production, hunger and malnutrition. © Springer Science+Business Media B.V. 2012. All rights reserved.
To limit global warming to <2 °C we must reduce the net amount of CO2 we release into the atmosphere, either by producing less CO2 (conventional mitigation) or by capturing more CO2 (negative emissions). Here, using state-of-the-art carbon-climate models, we quantify the trade-off between these two options in RCP2.6: an Intergovernmental Panel on Climate Change scenario likely to limit global warming below 2 °C. In our best-case illustrative assumption of conventional mitigation, negative emissions of 0.5-3 Gt C (gigatonnes of carbon) per year and storage capacity of 50-250 Gt C are required. In our worst case, those requirements are 7-11 Gt C per year and 1,000-1,600 Gt C, respectively. Because these figures have not been shown to be feasible, we conclude that development of negative emission technologies should be accelerated, but also that conventional mitigation must remain a substantial part of any climate policy aiming at the 2-°C target.
The useful energy services and energy density value of fossil carbon fuels could be retained for longer timescales into the future if their combustion is balanced by CO 2 recapture and storage. We assess the global balance between fossil carbon supply and the sufficiency (size) and capability (technology, security) of candidate carbon stores. A hierarchy of value for extraction-to-storage pairings is proposed, which is augmented by classification of CO 2 containment as temporary (<1,000 yr) or permanent (>100,000 yr). Using temporary stores is inefficient and defers an intergenerational problem. Permanent storage capacity is adequate to technically match current fossil fuel reserves. However, rates of storage creation cannot balance current and expected rates of fossil fuel extraction and CO 2 consequences. Extraction of conventional natural gas is uniquely holistic because it creates the capacity to re-inject an equivalent tonnage of carbon for storage into the same reservoir and can re-use gas-extraction infrastructure for storage. By contrast, balancing the extraction of coal, oil, biomass and unconventional fossil fuels requires the engineering and validation of additional carbon storage. Such storage is, so far, unproven in sufficiency.
The size of the terrestrial sink remains uncertain. This uncertainty presents a challenge for projecting future climate–carbon cycle feedbacks1, 2, 3, 4. Terrestrial carbon storage is dependent on the availability of nitrogen for plant growth5, 6, 7, 8, and nitrogen limitation is increasingly included in global models9, 10, 11. Widespread phosphorus limitation in terrestrial ecosystems12 may also strongly regulate the global carbon cycle13, 14, 15, but explicit considerations of phosphorus limitation in global models are uncommon16. Here we use global state-of-the-art coupled carbon–climate model projections of terrestrial net primary productivity and carbon storage from 1860–2100; estimates of annual new nutrient inputs from deposition, nitrogen fixation, and weathering; and estimates of carbon allocation and stoichiometry to evaluate how simulated CO2 fertilization effects could be constrained by nutrient availability. We find that the nutrients required for the projected increases in net primary productivity greatly exceed estimated nutrient supply rates, suggesting that projected productivity increases may be unrealistically high. Accounting for nitrogen and nitrogen–phosphorus limitation lowers projected end-of-century estimates of net primary productivity by 19% and 25%, respectively, and turns the land surface into a net source of CO2 by 2100. We conclude that potential effects of nutrient limitation must be considered in estimates of the terrestrial carbon sink strength through the twenty-first century.
Stabilization of atmospheric greenhouse gas (GHG) concentrations at a safe level is a paradigm that the scientific and policy communities have widely adopted for addressing the problem of climate change. However, aiming to stabilize concentrations at a single target level might not be a robust
This paper provides a novel and comprehensive model-based assessment of possible outcomes of the Durban Platform negotiations with a focus on emissions reduction requirements, the consistency with the 2°C target and global economic impacts. The Durban Platform scenarios investigated in the LIMITS study — all assuming the implementation of comprehensive global emission reductions after 2020, but assuming different 2020 emission reduction levels as well as different long-term concentration targets — exhibit a probability of exceeding the 2°C limit of 22–41% when reaching 450 (450–480) ppm CO2e, and 35–59% when reaching 500 (480–520) ppm CO2e in 2100. Forcing and temperature show a peak and decline pattern for both targets. Consistency of the resulting temperature trajectory with the 2°C target is a societal choice, and may be based on the maximum exceedance probability at the time of the peak and the long run exceedance probability, e.g., in the year 2100. The challenges of implementing a long-term target after a period of fragmented near-term climate policy can be significant as reflected in steep reductions of emissions intensity and transitional and long-term economic impacts. In particular, the challenges of adopting the target are significantly higher in 2030 than in 2020, both in terms of required emissions intensity decline rates and economic impacts. We conclude that an agreement on comprehensive emissions reductions to be implemented from 2020 onwards has particular significance for meeting long-term climate policy objectives.
This paper examines the near- and the long-term contribution of regional and sectoral bioenergy use in response to both regionally diverse near-term policies and longer-term global climate change mitigation policies. The use of several models provides a source of heterogeneity in terms of incorporating uncertain assumptions about future socioeconomics and technology, as well as different paradigms for how different regions and major economies of the world may respond to climate policies. The results highlight the heterogeneity and versatility of bioenergy itself, with different types of resources and applications in several energy sectors. In large part due to this versatility, the contribution of bioenergy to climate mitigation is a robust response across all models. Regional differences in bioenergy consumption, however, highlight the importance of assumptions about trade in bioenergy feedstocks and the influence of energy and climate policies. When global trade in bioenergy is possible, regional patterns of bioenergy use follow global patterns. When trade is assumed not to be feasible, regions with high bioenergy supply potential tend to consume more bioenergy than other regions. Energy and climate policies, such as renewable energy targets, can incentivize bioenergy use, but specifics of the policies will dictate the degree to which this is true. For example, renewable final energy targets, which include electric and non-electric renewable sources, increase bioenergy use in all models, while electric-only renewable targets have a mixed effect on bioenergy use across models.
The levels of investment needed to mobilize an energy system transformation and mitigate climate change are not known with certainty. This paper aims to inform the ongoing dialogue and in so doing to guide public policy and strategic corporate decision making. Within the framework of the LIMITS integrated assessment model comparison exercise, we analyze a multi-IAM ensemble of long-term energy and greenhouse gas emissions scenarios. Our study provides insight into several critical but uncertain areas related to the future investment environment, for example in terms of where capital expenditures may need to flow regionally, into which sectors they might be concentrated, and what policies could be helpful in spurring these financial resources. We find that stringent climate policies consistent with a 2°C climate change target would require a considerable upscaling of investments into low-carbon energy and energy efficiency, reaching approximately 30–1.1 trillion annually. This represents an increase of some 10–0.8 trillion per year, beyond what investments might otherwise be in a reference scenario that assumes the continuation of present and planned emissions-reducing policies throughout the world. In other words, a substantial "clean-energy investment gap" of some 523 billion). Unless the gap is filled rather quickly, the 2°C target could potentially become out of reach.
Integrated assessment models can help in quantifying the implications of international climate agreements and regional climate action. This paper reviews scenario results from model intercomparison projects to explore different possible outcomes of post-2020 climate negotiations, recently announced pledges and their relation to the 2 °C target. We provide key information for all the major economies, such as the year of emission peaking, regional carbon budgets and emissions allowances. We highlight the distributional consequences of climate policies, and discuss the role of carbon markets for financing clean energy investments, and achieving efficiency and equity.
Climate stabilization scenarios emphasize the importance of land-based mitigation to achieve ambitious mitigation goals. The stabilization scenarios informing the recent IPCC's Fifth Assessment Report suggest that bioenergy could contribute anywhere between 10 and 245 EJ to climate change mitigation in 2100. High deployment of bioenergy with low life-cycle GHG emissions would enable ambitious climate stabilization futures and reduce demands on other sectors and options. Bioenergy with carbon capture and storage (BECCS) would even enable so-called ‘negative emissions’, possibly in the order of magnitude of 50% of today's annual gross emissions. Here I discuss key assumptions that differ between economic and ecological perspectives. I find that high future yield assumptions, plausible in stabilization scenarios, look less realistic when evaluated in biophysical metrics. Yield assumptions also determine the magnitude of counterfactual land carbon stock development and partially determine the potential of BECCS. High fertilizer input required for high yields would likely hasten ecosystem degradation. I conclude that land-based mitigation strategies remain highly speculative; a constant iteration between synoptic integrated assessment models and more particularistic and fine-grained approaches is a crucial precondition for capturing complex dynamics and biophysical constraints that are essential for comprehensive assessments.This article is protected by copyright. All rights reserved.
Elevated concentrations of atmospheric greenhouse gases (GHGs), particularly carbon dioxide (CO2), have affected the global climate. Land-based biological carbon mitigation strategies are considered an important and viable pathway towards climate stabilization. However, to satisfy the growing demands for food, wood products, energy, climate mitigation and biodiversity conservation-all of which compete for increasingly limited quantities of biomass and land-the deployment of mitigation strategies must be driven by sustainable and integrated land management. If executed accordingly, through avoided emissions and carbon sequestration, biological carbon and bioenergy mitigation could save up to 38 billion tonnes of carbon and 3-8% of estimated energy consumption, respectively, by 2050.
Today, the burning of fossil fuels, including coal, oil, and gas meets more than 85% of the world's commercial energy needs. Our planet has entered a period of changing climate never before experienced in recorded human history, primarily caused by the rapid build-up of carbon dioxide (CO2) in the atmosphere from fossil fuel burning. The scientific community agrees that there are a number of risks associated with climate change, including sea level rise, drought, heat waves, more severe storms, increasing precipitation intensity, and ocean acidification. Natural processes will eventually return Earth to pre-industrial CO2 levels once emissions cease; however, those processes operate on millennial time scales or longer. Therefore, the climate changes and impacts from elevated CO2 levels will persist for millennia if humans fail to intervene. Reducing CO2 emissions to the atmosphere will require a portfolio of solutions, some of which include CO2 capture and storage (CCS), biomass-sourced energy (e.g., bioenergy), increased dependence on renewables, reduction in deforestation, and efficiency increases. And although there are ongoing efforts on climate adaptation in many communities, both humans and ecosystems face substantial challenges in adapting to the varied impacts of climate change over the coming century. For that reason, it is crucial to examine other strategies for limiting the risks from climate change, even as mitigation and adaptation remain the primary emphasis. Also, if society continues its trajectory on increased fossil fuel dependence in the coming decades, mitigation or avoidance of CO2 emissions will no longer be the primary solution for reducing the risks associated with climate change; rather, the removal of CO2 from the atmosphere (CDR) will be required. Strategies for CDR may include linking bioenergy with CCS, direct air capture, land management, and accelerated weathering. These topics will be discussed, in particular, in terms of their impact and related potential for significantly reducing atmospheric CO2 on a time scale of interest.
Bioenergy is expected to play an important role in the future energy mix as it can substitute fossil fuels and contribute to climate change mitigation. However, large-scale bioenergy cultivation may put substantial pressure on land and water resources. While irrigated bioenergy production can reduce the pressure on land due to higher yields, associated irrigation water requirements may lead to degradation of freshwater ecosystems and to conflicts with other potential users. In this article, we investigate the trade-offs between land and water requirements of large-scale bioenergy production. To this end, we adopt an exogenous demand trajectory for bioenergy from dedicated energy crops, targeted at limiting greenhouse gas emissions in the energy sector to 1100 Gt carbon dioxide equivalent until 2095. We then use the spatially explicit global land- and water-use allocation model MAgPIE to project the implications of this bioenergy target for global land and water resources. We find that producing 300 EJ yr−1 of bioenergy in 2095 from dedicated bioenergy crops is likely to double agricultural water withdrawals if no explicit water protection policies are implemented. Since current human water withdrawals are dominated by agriculture and already lead to ecosystem degradation and biodiversity loss, such a doubling will pose a severe threat to freshwater ecosystems. If irrigated bioenergy production is prohibited to prevent negative impacts of bioenergy cultivation on water resources, bioenergy land requirements for meeting a 300 EJ yr−1 bioenergy target increase substantially (+ 41%) – mainly at the expense of pasture areas and tropical forests. Thus, avoiding negative environmental impacts of large-scale bioenergy production will require policies that balance associated water and land requirements.
The human influence on the global hydrological cycle is now the dominant force behind changes in water resources across the world and in regulating the resilience of the Earth system. The rise in human pressures on global freshwater resources is in par with other anthropogenic changes in the Earth system (from climate to ecosystem change), which has prompted science to suggest that humanity has entered a new geological epoch, the Anthropocene. This paper focuses on the critical role of water for resilience of social-ecological systems across scales, by avoiding major regime shifts away from stable environmental conditions, and in safeguarding life support systems for human wellbeing. It highlights the dramatic increase of water crowding; near-future challenges for global water security and expansion of food production in competition with carbon sequestration and biofuel production. It addresses the human alterations of rainfall stability, due to both land use changes and climate change; the ongoing overuse of blue water, reflected in river depletion, expanding river basin closure, groundwater overexploitation, and water pollution risks. The rising water turbulence in the Anthropocene changes the water research and policy agenda, from a water resource efficiency to a water resilience focus. This includes integrated land and water stewardship to sustain wetness-dependent ecological functions at the landscape scale and a stronger emphasis on green water management for ecosystem services. A new paradigm of water governance emerges, encouraging land use practices that explicitly take account of the multifunctional roles of water, with adequate attention to planetary freshwater boundaries and cross-scale interactions.
Bioenergy with carbon capture and storage could be used to remove carbon dioxide from the atmosphere. However, its credibility as a climate change mitigation option is unproven and its widespread deployment in climate stabilization scenarios might become a dangerous distraction.
The agriculture, forestry and other land use (AFOLU) sector is responsible for approximately 25% of anthropogenic GHG emissions mainly from deforestation and agricultural emissions from livestock, soil and nutrient management. Mitigation from the sector is thus extremely important in meeting emission reduction targets. The sector offers a variety of cost-competitive mitigation options with most analyses indicating a decline in emissions largely due to decreasing deforestation rates. Sustainability criteria are needed to guide development and implementation of AFOLU mitigation measures with particular focus on multifunctional systems that allow the delivery of multiple services from land. It is striking that almost all of the positive and negative impacts, opportunities and barriers are context specific, precluding generic statements about which AFOLU mitigation measures have the greatest promise at a global scale. This finding underlines the importance of considering each mitigation strategy on a case-by-case basis, systemic effects when implementing mitigation options on the national scale, and suggests that policies need to be flexible enough to allow such assessments. National and international agricultural and forest (climate) policies have the potential to alter the opportunity costs of specific land-uses in ways that increase opportunities or barriers for attaining climate change mitigation goals. Policies governing practices in agriculture and in forest conservation and management need to account for both effective mitigation and adaptation and can help to orient practices in agriculture and in forestry toward global sharing of innovative technologies for the efficient use of land resources. Different policy instruments, especially economic incentives and regulatory approaches, are currently being applied however for its successful implementation it is critical to understand how land use decisions are made and how new social, political and economic forces in the future will influence this process. This article is protected by copyright. All rights reserved.