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![Illustrative McKelvey diagram showing CDR availability based on permanence and economic feasibility (adapted from [82]).](publication/376467767/figure/fig2/AS:11431281296991689@1734073153468/Illustrative-McKelvey-diagram-showing-CDR-availability-based-on-permanence-and-economic.jpg)
Illustrative McKelvey diagram showing CDR availability based on permanence and economic feasibility (adapted from [82]).
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Carbon Dioxide Removal (CDR) is an emerging activity with extremely limited deployment to date, but which is mathematically required to achieve net (rather than true) zero or negative anthropogenic contribution to climate change. The required scale of CDR, however, depends on decisions about what activities will be allowed to emit greenhouse gases...
Citations
... In contrast to atmospheric GHG removal processes, which directly reduce concentrations of accumulated GHGs in the atmosphere, these 'negative' avoidance-based emissions do not actually reduce atmospheric GHG levels: rather, they rely on claims that but for the project in question, such levels would have been even higher. As such, they are highly sensitive to assumptions about counterfactual futures and do not actually produce negative emissions from a climate perspective (Grubert and Talati 2024). For example, consider a large dairy operation that involves a manure lagoon. ...
Prominent clean energy tax credits in the United States (U.S.) could drive large expenditures that materially increase greenhouse gas (GHG) emissions if their implementing regulations assign negative values to avoided GHG emissions and allow projects to offset other supply chain emissions on this basis. Most notably, we find that assigning negative GHG intensities to biogenic- and fossil-origin methane feedstocks and allowing such feedstocks to be blended with natural gas could support about 35 million metric tonnes of gray hydrogen production per year under the Section 45V tax credit. These practices would come at a taxpayer cost of ∼$1 trillion over 10 years of tax credit eligibility and cause excess emissions of ∼3 billion tonnes carbon dioxide-equivalent (CO2e) above scenarios that impose strict methane controls. Both the clean hydrogen (Section 45V) and clean electricity (Section 45Y) production tax credits use life cycle emissions criteria to direct potentially trillions of dollars in federal tax expenditures. Life cycle analysis is a decision support tool that is increasingly prominent in energy and environmental policies, but it is not an objective, quantitative calculator. Seemingly minor choices about life cycle system boundaries and baseline assumptions, such as whether unabated methane emissions are assumed to continue indefinitely, have gigatonne-scale effects on expected GHG outcomes. We find that risks are more significant for hydrogen than clean electricity due both to the scale of feedstock availability relative to market size and tax credit value relative to commodity prices. Methane feedstocks that are inappropriately assigned negative emissions intensity could dominate U.S. hydrogen production via conventional steam methane reformation, preventing the innovation-oriented 45V tax credit from encouraging development of higher-cost electrolysis technology. For both tax credits, if eligibility rules qualify emitting technologies based on offsets, long-lived facilities would have no incentive to continue offsetting once tax credit incentives end, risking lock-in of methane-based infrastructure.
... Determining which emissions persist is not simply a technical issue, nor even one of relative cost; it is fundamentally one of social value. Our current approach may enable continuing emissions from fossil fuel production or 'luxury' emissions like air travel (Grubert & Talati, 2024), rather than counterbalancing emissions from the provision of basic necessities to those in need. Rules of legitimacy are required that define what types of residual emissions can defensibly be justified as 'necessary' for compensation via carbon removal. ...
... Questions of 'which purposes to prioritize' raise difficult trade-offs, with important implications for justice. As Grubert and Talati (2024) argue, it should not be wealthy nations and large companies who get to decide how limited carbon removal resources (e.g. land, energy, minerals) are spent. ...
... land, energy, minerals) are spent. The limited 'supply' of carbon removal should instead orient towards the Global South's benefit -e.g. it should be used to allow Global South countries to decarbonize more slowly than wealthy nations (in accordance with historical harms), or to support food security, and critical wellbeing and health impacts for the world's poorest (Grubert & Talati, 2024). However, shifting towards these justice-oriented priorities is difficult in the context of carbon market models, where the commodification of environmental resources creates a price incentive and decisions about the allocation of risks and benefits driven by the spending choices of consumers and businesses. ...
... However, its combustion releases carbon dioxide and other pollutants, contributing to environmental challenges (Liu et al., 2024a;Syrtsova et al., 2024). In contrast, biomass, used as a fuel source, offsets carbon dioxide emissions by capturing an equivalent amount of carbon dioxide during its growth cycle (Grubert & Talati, 2024). This zero-net carbon cycle positions biomass as a potentially more environmentally sustainable option, provided that carbon emissions during its production are minimized (Aravindhan et al., 2024;Li et al., 2023). ...
This study offers a comprehensive comparative analysis of the elemental and proximate compositions of coal and biomass fuels, including Indo Coal, HBFL, SBP, and SBFL, highlighting their implications for sustainable energy production. Key elements such as aluminum, arsenic, boron, barium, calcium, chromium, copper, iron, potassium, lithium, magnesium, manganese, molybdenum, sodium, nickel, lead, antimony, silicon, and tin exhibit significant variations, emphasizing the importance of understanding each fuel source, particularly in co-firing applications. Combustion residues from these fuels show diverse elemental compositions, necessitating careful environmental management of elements like arsenic, lead, and chromium. Proximate analysis reveals distinctive characteristics, with variability in ash content affecting combustion efficiency and environmental considerations. The study finds that co-firing biomass with coal can significantly reduce NOx and SOx levels, with sulfur content in mixtures decreasing by up to 18%, leading to a potential 30% reduction in SO2 emissions. CO2 emissions could also be reduced by up to 51.21% as the biomass-to-coal ratio increases. Despite an 11% to 19% decrease in energy due to moisture imbalance, this can be optimized with technological advancements. Economic benefits are clear, as blending 2% of biomass can save 6.34% in both fuel consumption and purchase costs, with the highest cost-saving ratio of 72.87% achieved at a 20% blending ratio. Notably, most savings arise from the lower biomass purchase costs (Rs. 5000–6000 per ton) compared to coal (Rs. 15000–18000 per ton). However, technical challenges such as combustor fouling and corrosion from biomass ash must be addressed. Further research, particularly in thermal kinetic modeling, is recommended to examine the combustion characteristics of coal-biomass blends under controlled conditions. The progression from initial studies to long-term demonstrations indicates a promising future for co-firing technology, facilitating its widespread adoption in the industry at an optimal cost.
... This of course is the logic that underpins offsetting mechanisms. It allows the prioritisation of short-term profitability over ambitious climate mitigation, and implicitly allocates CDR to those that can afford it (Grubert and Talati, 2024). In the absence of restrictive policy measures, this means that some sectors or industries can continue emitting GHGs as long as they purchase sufficient amounts of (CDR) credits. ...
... However, the majority of currently operational mechanisms in carbon markets mainly support lower-cost conventional CDR methods that build on so-called nature-based solutions (Hickey et al., 2023), while novel (nonnature-based) CDR methods with more durable carbon storage have received less financing. In the most recent years, government financing schemes are being prepared and deployed to promote deployment of novel CDR methods, for example, in Denmark, Norway, Sweden, the United Kingdom, and the US (DESNZ, 2023;Grupert and Talati, 2023;Hickey et al., 2023;. Without a significant growth in financing, CDR will fail to scale sufficiently. ...
Limiting global warming to close to 1.5°C by 2100 requires deep and rapid greenhouse gas emission reductions and carbon dioxide removals (CDR) on a massive scale, presenting a remarkable scaling challenge. This paper focuses on the financing of bioenergy with carbon capture and storage (BECCS) in Sweden. BECCS is one of the most prominent CDR methods in 1.5°C-compatible global emission scenarios and has been assigned a specific role in Swedish policy for net-zero. A Swedish state support system for BECCS based on results-based payments is planned. Furthermore, demand for CDR-based carbon credits is on the rise on the voluntary carbon markets (VCM) for use towards voluntary mitigation targets. Risks involved with the current Swedish policies are analysed, specifically for the co-financing of BECCS by the planned state support and revenues from the VCM. We find that with the current policies, state support systems will subsidise carbon credit prices on the VCM. We argue that such subsidisation can lower decarbonisation efforts by lowering the internal carbon price set by actors, thus undermining environmental integrity. It is concluded that proportional attribution should be applied, i.e., attributing mitigation outcomes to the state support and VCM revenue in proportion to their financial contribution to the CDR achieved. The attribution analysis should be accompanied by adjustments in national greenhouse gas accounting so that mitigation outcomes that are issued as carbon credits and used for offsetting are not double claimed (i.e., not used by both a nation and a non-state actor on the VCM towards their respective mitigation targets). If proportional attribution and adjustments in national GHG accounting are not implemented, the credibility and environmental integrity of offsetting claims made by carbon credit users are eroded. We recommend that action is taken to operationalise and implement proportional attribution to allow for co-financing of BECCS projects while maintaining environmental integrity. Wider implications for our recommendations beyond the case of Swedish BECCS are also analysed.
... Carbon removal does not have unlimited potential for deployment-rather, it should be thought of as 'precious' and a scarce option, due to resource limitations, particularly around space, energy, and physical materials 46 . Carbon removal will be expensive and resourceintensive, taking dollars from other important investments needed for decarbonization and renewables that might otherwise be used to substitute for fossil fuels. ...
... Our current understanding is limited on what the upper bounds of 'total possible carbon removal' might be, but the limited nature of possible deployment necessitates that we make decisions about what to do carbon removal for: do we do it to compensate for "luxury" emissions 46 , or emissions from production of staple food crops? ...
... Indeed, the kind of massive economic transition involved in something like carbon removal has, according to Christian Parenti, "always require[d] state coordination and subsidy, if not outright nationalization" 20 . Furthermore, there is a strong case to be made that carbon removal should be understood as a public good or service 19,46 , something that should be provided for the benefit of society rather than as a commodity for private industry to profit from. ...
... Guo et al. (2023) demonstrate practical example of how EW impacts can be quantified in agricultural settings, aligning methodologies with MRV principles for tracking and verifying the impacts of EW on CDR and agricultural productivity. Power et al. (2024) and Grubert and Talati (2024) discuss the importance of developing robust MRV protocols to track and verify CO 2 sequestration rates, highlighting the need for geochemical modeling and innovative measurement methods. Rieder et al. (2024) introduce a novel approach to MRV by investigating soil electrical conductivity and volumetric water content as proxies for tracking alkalinity and dissolved inorganic carbon, offering a cost-effective alternative to traditional methods. ...
As the urgency to address climate change intensifies, the exploration of sustainable negative emission technologies becomes imperative. Enhanced weathering (EW) represents an approach by leveraging the natural process of rock weathering to sequester atmospheric carbon dioxide (CO2) in agricultural lands. This review synthesizes current research on EW, focusing on its mechanisms, influencing factors, and pathways for successful integration into agricultural practices. It evaluates key factors such as material suitability, particle size, application rates, soil properties, and climate, which are crucial for optimizing EW’s efficacy. The study highlights the multifaceted benefits of EW, including soil fertility improvement, pH regulation, and enhanced water retention, which collectively contribute to increased agricultural productivity and climate change mitigation. Furthermore, the review introduces Monitoring, Reporting, and Verification (MRV) and Carbon Dioxide Removal (CDR) verification frameworks as essential components for assessing and enhancing EW’s effectiveness and credibility. By examining the current state of research and proposing avenues for future investigation, this review aims to deepen the understanding of EW’s role in sustainable agriculture and climate change mitigation strategies.
Despite uncertainties about its feasibility and desirability, start-up companies seeking to profit from solar geoengineering have begun to emerge. One company is releasing balloons filled with sulfur dioxide to sell “cooling credits”, claiming that the cooling achieved when 1 g of SO2 is released is equivalent to offsetting one ton of carbon dioxide for one year. Another aspires to deliver returns to investors from the development of a proprietary aerosol for dispersal in the stratosphere. Such for-profit solar geoengineering enterprises should not be understood merely as rogue opportunists. These proposals are not only scientifically questionable, and premature in the absence of effective governance, but they are a predictable consequence of neoliberal, market-driven climate governance. The structures and incentives of market-based climate policy – circumscribed by neoliberalism's emphasis on technological innovation, venture capital, and the marketization of environmental goods – have generated repeated efforts to profit from various forms of geoengineering. With a climate governance regime wherein private, for-profit actors significantly influence and weaken climate policy, de facto governance of solar geoengineering has emerged, dominated by actors linked to Silicon Valley funders and ideologies. Without more explicit efforts to curb the power of private sector actors, including commercial geoengineering bans and non-use provisions, pursuit of techno-market “solutions” could lead to both inadequate mitigation and increasingly risky reliance on geoengineering.
This commentary explains why market signals are insufficient to support a zero greenhouse gas emissions outcome: markets function by sorting based on cost and/or profitability, and there is nothing to sort when the target is zero. It then describes why sorting is ineffective even on the path to zero emissions, given that the most societally critical emissions (i.e. those that should be allowed to continue the longest) are not necessarily the most financially costly to eliminate. This observation also means that even for a net-zero emissions target, where some emissions do continue, markets are unlikely to identify the most societally preferred emissions to preserve without an exogenous declaration of preference, and could distort the development of potentially critical industrial functions along the way. Finally, the commentary concludes with an alternative proposal, for a centrally coordinated transition towards a known end goal – a major difference from settings where markets perform well.
Arid and semiarid regions cover more than one‐third of the land surface, where the interplay between water, land use, and management strongly influences carbon (C) sequestration. Yet, information on the C management practices and how local biophysical conditions affect the C sequestration potential is limited. We explored the opportunities, research gaps, and future directions of land C sequestration in arid and semiarid regions, using New Mexico as an example. We also identified the major land use types and their potential for C storage and sequestration. Our results showed that innovations in cropland and rangeland management, protection of existing forests, and restoration of degraded forest lands after drought and wildfire enhanced C sequestration in arid and semiarid lands. Landscape‐scale C balance studies with fine‐scale mapping, improving water and nutrient use efficiency, and policy incentives to support farms will unlock the full potential of C sequestration in croplands, rangelands, and forest lands. Future research should focus on the response of land management practices to climate anomalies and their potential to sequester C and offset greenhouse gas emissions as a natural climate solution in arid and semiarid regions.
