Negative Emissions Research Articles

Techno-economic analysis of a combined power plant CO2 capture and direct air capture concept for flexible power plant operation

The electric power sector must be deeply decarbonized at a reasonable cost to achieve economy-wide decarbonization goals via sustainable electrification of other sectors. While variable renewable energy generation is expected to dominate grid decarbonization efforts, variability creates the need for supply- and demand-side technologies that can operate flexibly to balance the system. This paper proposes a new concept for power plant flue gas capture integrated with a novel lime-based direct air capture technology to enable flexible operation of the power plant and achieve negative emissions under all operating scenarios. Steady-state models are developed, and sensitivity analyses are conducted on key process variables to investigate system performance. The results, presented at three different power plant loading levels (100 %, 40 %, and 0 %), demonstrate negative emissions of -0.188 tCO2/MWh at 100 % loading and -2.087 tCO2/MWh at 40 % loading. Economic modeling suggests the need for carbon credits exceeding $170/tCO2 to achieve positive net present values.

Assessing the CO2 capture potential for waste-fired CHP plants

The integration of CO2 capture with biomass-fired power plants has attracted much attention due to its ability to achieve negative emissions. Waste-fired combined heat and power (CHP) plants with CO2 capture, on the other hand, has received little attention, and their potential remains unclear. This study aims to identify the possible range of the amount of captured CO2 and investigate the impact of CO2 capture on the performance of waste-fired CHP plants. Since heat is the primary product of CHP plants, it is important to maintain heat production unchanged when CO2 capture is integrated. Based on this prerequisite, two operating strategies (OS) were investigated, which correspond to the upper and lower boundaries of CO2 capture: OS1 was to maximize the amount of captured CO2 while keeping the heat supplied to the district heating (DH) network unchanged; and OS2 was to maximize CO2 capture while keeping both supplied heat and generated electricity unchanged. To obtain more accurate results regarding the CO2 capture, a dynamic model developed in Aspen Hysys™ was utilized to simulate monoethanolamine (MEA) based chemical absorption for CO2 capture. By using real dynamic data from a waste-fired CHP plant, dynamic simulation results showed that the highest amount of captured CO2, which was achieved in OS1, was 401 kton/year, corresponding to a CO2 capture ratio of 82%; while the lowest amount of captured CO2, which was achieved in OS2, was 99 kton/year, corresponding to a CO2 capture ratio of 20%. For OS1, the electricity generation was substantially decreased by 61%. When determining the negative emission, the emission resulted from the share of fossil fuel in the waste needs to be excluded. For the studied CHP plant, the fossil share was around 45%. As a result, only OS1 can achieve the negative emission, which was 181 kton/year; while OS2 still led to positive emissions. Compared to the plant without CO2 capture, the carbon intensity of heat was reduced from 0.405 ton/MWh to 0.091 ton/MWh in OS1 and 0.351 ton/MWh in OS2, while the carbon intensity of electricity was reduced from 0.409 ton/MWh to 0.072 ton/MWh in OS1 and 0.343 ton/MWh in OS2.

Multi-variable study of a novel multigeneration system using biogas separation unit and LNG cold energy utilization, producing electricity, cooling, heat, fresh water, liquid CO2, biomethane, and methanol

Biogas fuel has gained recognition as a highly suitable alternative to fossil fuels, attributed to its renewable nature and remarkable energy density. Biogas fuel utilization facilitates the integration of combined energy systems equipped with multi-generational structures, rendering them suitable for long-term planning and management. Hence, this study presents a unique approach to using biogas for multigeneration, exhibiting enhanced thermodynamic efficiencies and negative carbon dioxide emissions. To achieve the stated objective, an innovative system is devised that involves the utilization of a biogas separation unit in integration with several other components, including a LNG cold energy utilization unit, an ammonia Rankine cycle, a desalination unit, a Kalina cycle, a solid oxide electrolyzer cell, a biomethane combined cycle, and a methanol synthesis unit. The newly devised configuration is simulated through the Aspen HYSYS software and assessed from energy, exergy, environmental, and economic considerations. Based on the research findings, the suggested methodology exhibits energy and exergy efficiencies of 91% and 83%, correspondingly. Furthermore, the evaluation of the entire unit cost of the product and the levelized energy cost reveals values of 4.81 $/GJ and 0.033 $/kWh, respectively. The carbon dioxide emission intensity of the newly implemented process is calculated to be − 0.1041 kg/kWh. The economic aspects reveal a favorable net present value of 1470.6 M$ and a payback period of 5.29 years.

The Cost to Consumers of Carbon Capture and Storage—A Product Value Chain Analysis

High-cost abatement measures to mitigate greenhouse gas emissions in the basic commodity industry is known to result in substantial increases in the production costs. Consequently, investments in such measures are lagging behind what is required to make deep emission cuts in line with the Paris Agreement. As high-cost abatement measures (such as Carbon Capture and Storage; CCS) are perceived as expensive for the basic commodity producer, this study investigates the impacts down-stream of the product value chain when assuming full cost pass-through (i.e., the cost increase related to basic commodity production is fully passed on down-stream of the product chain to the end-consumer). We investigate the effects on both costs, by means of a techno-economic assessment, and carbon footprints, using a Life Cycle Assessment (LCA), along the product value chain for the case of post-combustion CCS applied to the cement, pulp, Waste-to-Energy (WtE), and refinery industries, towards abating fossil- and process-related emissions and generating negative emissions. Here, we analyse the product value chains that involve cement to a high-speed railway, pulp to a disposable baby diaper, WtE in connection with housing and plastic products, and refineries to different transportation solutions (truck transport and air-freight). The results show that even though the costs for producing basic commodities can increase significantly (200% for cement, 75% for pulp, 230% for heat, and 6–37% for refinery products) when implementing CCS, the increases in prices for end-users are marginal (1% for the railway, 3% for the disposable baby diaper, 1% for the housing, 0.4% for truck transport and 2% for air-freight). Simultaneously, the carbon footprint associated with the end-use may be reduced by up to 36% for the railway, 31% for the diaper, 80% for the housing, and 3–23% for the refinery cases.

Exploring pathway to achieving carbon neutrality in China under uncertainty

China has announced its long-term goal of achieving carbon-neutrality before 2060, and it is necessary to identify the main driving forces of carbon emission, so that future carbon emission can be projected and effective measures to reduce carbon emission can be identified under uncertainty. Using a structural decomposition analysis model, China’s CO2 emission change within the period 2002–2017 were decomposed into the changes of six factors, classified as efficiency effect, structure effect and scale effect, and the key driving forces of CO2 emission are identified. By aggregating the driving forces, the future CO2 emissions are projected and the potential contribution of each driving force to reaching carbon–neutral is examined under uncertainty. The results show that in the period 2002–2017, economic growth increased CO2 emission by 11.4 billion tons as the largest driver of CO2 emission growth, while energy efficiency improvement contributed most to reducing CO2 emission by 3.38 billion tons. The projection analysis shows that multiple carbon reduction policies are needed simultaneously for China to achieve carbon neutrality, and accelerating the energy efficiency improvement and energy mix transformation plays key role. Moreover, negative carbon emission technologies is still necessary, which needs to contribute to reducing CO2 emission by at least 1.82 billion tons.

Status on CCS in Denmark

The presentation “Status on CCS in Denmark” will focus on the recent progress made in Denmark on CCS and provide insight into new initiatives underway. The CCS technology enjoys ample political support in Denmark. Since 2020 a number of political agreements has been reached, introducing three subsidy funds for CCS as well as a range of legislative and regulatory changes that has enabled Denmark to work towards establishing a full-scale CCS value chain with the aim of reaching its climate targets.It follows from the Danish CCS strategy that Denmark also strives to become a future European hub for CO2 storage. In that context, Denmark has entered into collaboration agreements with Belgium, the Netherlands, Norway, and Germany to promote CCS as a climate mitigation tool. Additionally, in 2022, Denmark signed an agreement with Belgium for the cross-border transportation of CO2 with the purpose of geological storage beneath the seabed. This agreement was the first of its kind in an international context. This year has been a particularly important year for CCS in Denmark. Recent developments include the awarding of the first full-scale offshore exploration licenses for CO2 storage, the first injection of CO2 in the Danish part of the North Sea has been completed in a pilot project, and the energy company, Ørsted, has secured a state-sponsored contract to establish the country's first full-scale CCS project. This initiative, valued at approximately 1.1 billion EUR, plans to commence CO2 capture in 2025. Moreover, a new tender for the NECCS (“Negative Emissions CCS”) subsidy fund was published in late August. The aim of the NECCS-fund is to achieve 0.5 million tons of negative CO2 emissions per year, through BECCS and/or DACCS by granting financial support to one or more projects at any scale. Also in late August, a new political proposal was introduced, containing new CCS-initiatives. Finally, new tenders for exploration and storage licenses are planned in the future.

Public perceptions of CCUS in Central and Eastern Europe – implications for community engagement

Carbon capture, utilization, and storage (CCUS) is emerging as a subject of major interest for EU climate policy due to their potential role in avoiding hard-to-abate CO2 emissions, as well as to lead to “negative emissions” through direct air capture or bioenergy with carbon capture and storage. Despite CCUS technologies being deployed since the 1970s, their widespread implementation is still challenged by a range of factors, including policy inertia, high costs, and relative novelty in the public discourse. In particular, as CCUS emerges slowly into the realm of public and political debate, opinions on these technologies and associated projects are easily changeable and affected by a range of factors, which make concerted public and community engagement extremely important for deploying them where they matter most.The Central and Eastern Europe (CEE) region is characterized by a higher-than-average economic dependence on heavy industry, old assets and infrastructure, and a high occurrence of regions where the transition to climate neutrality will have a significant impact on local economies, employment, and social welfare [1]. CCUS could play an important role in decarbonizing the heavy industry sectors of the region, particularly given the potentially significant storage capabilities of countries such as Romania and Poland, as well as emerging storage potential in the Black Sea and Eastern Mediterranean Sea. However, climate policy in these jurisdictions is sluggish, and there is a general failure to approach CCUS in a systematic way, with targeted application to sectors where it can have the highest impact, such as cement and oil refining. As a result, the public debate around CCUS is practically non-existent, and where public opinions do emerge, they may be significantly influenced by the context of a particular project and generate significant resistance based on the relationship with project developers, the amplification of perceived risks, and the lack of appropriate explanations of costs, benefits and risks. This in turn can lead to a reticence of political stakeholders to commit to deploying CCUS, causing the public debate to further stagnate and creating a vicious circle whereby opportunities to familiarize the public with these technologies (well in advance of their deployment) are missed.In order to deploy CCUS at pace and scale, as part of the catching-up climate policies of CEE countries, public perception of CCUS must be thoroughly researched and developed into appropriate guidelines for community engagement by project developers. There is experience in the region – the feasibility study for Romania’s planned Getica CCS demonstrator (subsequently abandoned) included comprehensive research into the perceptions of local communities, and a toolkit for communications around CCUS by project developers. Similarly, learnings from Poland’s failed Belchatow CCS project can serve to re-assess the state of public opinion on CCS, and how the local and national-level contexts for CCUS perceptions interact. The CEE region has significant potential for deploying CCUS, and public perception must be an integral part of planning as the region moves into the key decade of 2030-2040 for implementing large-scale projects.

Progress in lignocellulosic biomass valorization for biofuels and value‐added chemical production in the EU: A focus on thermochemical conversion processes

AbstractThe demand for sustainable energy sources has increased owing to environmental concerns, such as climate change, rising energy demand and rapid industrialization. Biomass utilization for bioenergy and value‐added chemical production has become essential for creating a circular low‐carbon bioeconomy and sustainable waste management techniques. This review focuses on thermochemical processes and analyzes the trends of biomass utilization for energy production in the EU over the last decade. It discusses the current state‐of‐the‐art of gasification, pyrolysis, advanced combustion and liquefaction technologies, and presents the individual challenges and prospects of each process. A comprehensive overview of previous studies related to each conversion technology is provided to pave the way for future thermochemical, biochemical and integrated biomass valorization studies. Additionally, the review discusses biomass thermochemical conversion processes, which are combined with carbon capture, such as gasification, liquefaction and pyrolysis. These processes offer the potential to achieve negative net atmospheric carbon emissions, which can contribute to global warming mitigation efforts.

Visible-Light-Active Iodide-Doped BiOBr Coatings for Sustainable Infrastructure.

The search for efficient materials for sustainable infrastructure is an urgent challenge toward potential negative emission technologies and the global environmental crisis. Pleasant, efficient sunlight-activated coatings for applications in self-cleaning windows are sought in the glass industry, particularly those produced from scalable technologies. The current work presents visible-light-active iodide-doped BiOBr thin films fabricated using aerosol-assisted chemical vapor deposition. The impact of dopant concentration on the structural, morphological, and optical properties was studied systematically. The photocatalytic properties of the parent materials and as-deposited doped films were evaluated using the smart ink test. An optimized material was identified as containing 2.7 atom % iodide dopant. Insight into the photocatalytic behavior of these coatings was gathered from photoluminescence and photoelectrochemical studies. The optimum photocatalytic performance could be explained from a balance between photon absorption, charge generation, carrier separation, and charge transport properties under 450 nm irradiation. This optimized iodide-doped BiOBr coating is an excellent candidate for the photodegradation of volatile organic pollutants, with potential applications in self-cleaning windows and other surfaces.

Gambling on unknown unknowns: Risk ethics for a climate change technofix

In this article, we critically engage with the risk ethics of attempting to mitigate climate change via a technofix, namely Negative Emissions Technologies (NETs) utilizing Synthetic Biology. Now that the IPCC has (belatedly) acknowledged climate overshoot as being inevitable, our dependency on NETs to avert runaway climate change has become critical. Given the scale of unknown unknowns at play when utilizing any such technofix, we present gambling as the most apt analogy to communicate the unprecedented realms of risk and uncertainty occasioned by any such action. Hence, we critique traditional normative ethics in order to illustrate how a germane climate ethics must face the largely uncertain and unpredictable risk that any climate change technofix would inevitably represent instead of advocating for outdated risk-averse positions. We conclude by showing that this approach is fundamental to developing impactful future ethics research on climate mitigation, and is required to mark a much-needed new direction for risk ethics in the Anthropocene.

Dual‐Role of Polyelectrolyte‐Tethered Benzimidazolium Cation in Promoting CO2/Pure Water Co‐Electrolysis to Ethylene

AbstractElectrochemical CO2 reduction reaction (CO2RR), as a promising route to realize negative carbon emissions, is known to be strongly affected by electrolyte cations (i.e., cation effect). In contrast to the widely‐studied alkali cations in liquid electrolytes, the effect of organic cations grafted on alkaline polyelectrolytes (APE) remains unexplored, although APE has already become an essential component of CO2 electrolyzers. Herein, by studying the organic cation effect on CO2RR, we find that benzimidazolium cation (Beim+) significantly outperforms other commonly‐used nitrogenous cations (R4N+) in promoting C2+ (mainly C2H4) production over copper electrode. Cyclic voltammetry and in situ spectroscopy studies reveal that the Beim+ can synergistically boost the CO2 to *CO conversion and reduce the proton supply at the electrocatalytic interface, thus facilitating the *CO dimerization toward C2+ formation. By utilizing the homemade APE ionomer, we further realize efficient C2H4 production at an industrial‐scale current density of 331 mA cm−2 from CO2/pure water co‐electrolysis, thanks to the dual‐role of Beim+ in synergistic catalysis and ionic conduction. This study provides a new avenue to boost CO2RR through the structural design of polyelectrolytes.

Dual-Role of Polyelectrolyte-Tethered Benzimidazolium Cation in Promoting CO2/Pure Water Co-Electrolysis to Ethylene.

Electrochemical CO2 reduction reaction (CO2RR), as a promising route to realize negative carbon emissions, is known to be strongly affected by electrolyte cations (i.e., cation effect). In contrast to the widely-studied alkali cations in liquid electrolytes, the effect of organic cations grafted on alkaline polyelectrolytes (APE) remains unexplored, although APE has already become an essential component of CO2 electrolyzers. Herein, by studying the organic cation effect on CO2RR, we find that benzimidazolium cation (Beim+) significantly outperforms other commonly-used nitrogenous cations (R4N+) in promoting C2+(mainly C2H4) production over copper electrode. Cyclic voltammetry and in-situ spectroscopy studies reveal that the Beim+ can synergistically boost the CO2 to *CO conversion and reduce the proton supply at the electrocatalytic interface, thus facilitating the *CO dimerization toward C2+formation. By utilizing the homemade APE ionomer, we further realize efficient C2H4 production at an industrial-scale current density of 331 mA cm-2 from CO2/pure water co-electrolysis, thanks to the dual-role of Beim+ in synergistic catalysis and ionic conduction. This study provides a new avenue to boost CO2RR through the structural design of polyelectrolytes.

Carbon-negative hydrogen production (HyBECCS): An exemplary techno-economic and environmental assessment

An exemplary techno-economic and environmental assessment of carbon-negative hydrogen (H2) production is carried out in this work. It is based on the so-called “dark photosynthesis” with carbon dioxide (CO2) capture and geological storage. As a special feature of the assessment, the economic consequences due to the impact on the global climate are taken into account. The results indicate that the example project would be capable of generating negative GHG emissions under the assumptions made. The amount is estimated to be 17.72 kgCO2 to be removed from the atmosphere per kilogram of H2 produced. The levelized costs of carbon-negative hydrogen are obtained, considering the economic impact of greenhouse gas emissions and removals. They are estimated to be 0.013 EUR/kWhH2. Compared to grey hydrogen from natural gas (0.12 EUR/kWhH2) and green hydrogen from electrolysis using renewable electricity (0.18 EUR/kWhH2), this shows a potential environmental-economic advantage of the considered example. Even without internalization of GHG impacts, an economic advantage of the project (0.12 EUR/kWhH2) over green hydrogen (0.17 EUR/kWhH2) is indicated. Compared to other NETs, the GHG removal efficiency is at the lower end of both BECCS and DACCS approaches.

Cryogenic CO2 capture from oxy-combustion flue gas by a hybrid distillation + physical absorption process

Hybrid flowsheets are defined, in the context of process intensification, as alternatives suitable for replacing energy-intensive separation methods through the combination of more than one unit operation. Given the undoubted importance of carbon capture, utilization, and storage (CCUS) in the next decades in the path to net-zero emissions and even negative emissions scenarios, this work focuses on CO2 capture from an oxy-combustion flue gas by means of a distillation-based hybrid process that avoids CO2 freeze-out, which is capable of delivering a liquid CO2-rich stream that can in principle be pumped to transport pressures with lower energy consumption in comparison to conventional post-combustion CO2 capture processes based on chemical absorption. A distillation-based process and a hybrid distillation + physical absorption process have been studied based on simulations in Aspen Hysys® V11 using the Peng-Robinson Equation of State and the “Acid Gas – Physical Solvents” thermodynamic property package. Firstly, a CO2 capture process based on cryogenic distillation has been proposed and a sensitivity analysis on the operating pressure and specified CO2 recovery has been performed in order to determine the most convenient configuration, balancing capital and operating costs. Then, a hybrid capture process has been proposed and analyzed, where cryogenic distillation is the bulk removal step and physical absorption into a mixture of homologues of the dimethylether of polyethylene glycol (DEPG) is the finishing step. Energy and economic analyses have shown that the hybrid process, delivering a CO2 product respecting the stringent purity requirement on the oxygen content for application for Enhanced Oil Recovery (EOR) and in the food industry is less energy intensive than the standalone cryogenic distillation, though it is characterized by higher capital costs.

How do system-wide net-zero scenarios compare to sector model pathways for the EU? A novel approach based on benchmark indicators and index decomposition analyses

The use of scenarios and quantitative modelling to identify pathways for energy system transformations in line with the Paris targets is well established in the field of energy and climate policy. The resulting decarbonization pathways depend on both assumptions and the type of model used (e.g., integrated assessment models, energy system, macro-econometric or bottom-up sector models). The objective of this article is to analyze how energy demand sectors in system-wide net-zero scenarios for the EU compare to the results of sector-specific models. To this end, a novel approach referred to as “sectoral benchmarking” is developed and applied, combining the application of standard indicators such as energy intensity, electrification rate or carbon intensity with an index decomposition analysis. The combined approach allows visualizing how system-wide decarbonization pathways differ from the sector models' pathways by bringing the model output in a harmonized format for an efficient comparison. The analysis compares pathways from four different modelling tools: two European system models, one of which is an energy system model (EU TIMES) and the other a macro-econometric model (NEMESIS); as well as two sector-specific models, for transport (ALADIN) and for the industry and building sectors (FORECAST). We evaluate the system model's net-zero scenarios by comparing them to a corridor given by the sector models' current policy and net-zero emission scenarios. This corridor represents what the sector models deem as plausible from their bottom-up perspective within the boundaries of current policies and ambitions to reach net-zero.Our results show that the system model net-zero pathways differ substantially from the sectoral perspective in all sectors. In the industry and building sectors, both system models' decarbonization ambitions are within the sector corridor, but the employed mitigation levers differ. In the industry sectors, the sectoral model achieves substantial CO2 emission reductions with electrification, while the system models use more bioenergy (EU TIMES) or more energy efficiency (NEMESIS). In the building sector, both system models rely mostly on electrification, while the sector models relies on biomass and some district heat and electrification. In the transport sector, both system models' decarbonization ambition is substantially lower than the sector model's.The observed differences are caused by a variety of factors, which we evaluate in this article. One reason is the system models' lower ambition to decarbonize the end-use sectors due to their ability to compensate with negative emission technologies across sectors. In addition, employed mitigation levers differ due to the models' differing capabilities to consider technologies as well as differences in the allocation of bioenergy to sectors.Our findings can be used to determine how the different types of models can inform each other and to make the diverging decarbonization pathways more transparent to policy-makers and other relevant stakeholders.

A multi-approach framework for developing feasible, viable, and sustainable hybrid energy systems in remote areas: The case of Con Dao island in Vietnam

In remote communities, hybrid energy systems are increasingly used to improve the reliability and renewability of power supply. The techno-economic analysis is often used to develop these promising energy systems, ignoring some performance indicators and environmental factors. This study proposes a multi-approach framework for developing operationally feasible, economically viable, and environmentally sustainable hybrid energy systems in remote areas. A case study is conducted on Con Dao Island in Vietnam to supply its electricity demand using six on-grid and off-grid hybrid energy systems. After finding the best techno-economic configurations of the six developed systems, they are subjected to multi-approach analysis and exhaustive comparison using a set of performance, economic, and environmental indicators. An off-grid hybrid energy system comprising photovoltaics, wind turbines, lead-acid batteries, and diesel generators has the lowest net present cost (109.7 million USD) to supply the predicted island's electricity consumption (with a total on-site electricity generation of 184.1 GWh/yr). However, this off-grid system indicates the highest excess energy fraction (55%), while the on-grid systems with the ability to export excess energy to the grid have no excess energy fraction. In terms of eco-friendliness, an on-grid hybrid energy system consisting of a high level of photovoltaics and wind turbines shows the best results, with a negative total environmental impact and CO2-eq emissions. This on-grid system shows the best cost of energy (0.1 USD/kWh) with approximately 450% less total environmental impact than the best off-grid system investigated, offsetting about 48.2 kilotonnes of CO2-eq/yr by exporting net emission-free electricity. Overall, the proposed framework can assist decision-makers in finding feasible, viable, and sustainable hybrid energy systems.

Expanding the Library of Ions for Moisture-Swing Carbon Capture.

Developing materials that can more efficiently and cheaply capture carbon dioxide from ambient atmospheric conditions is essential for improving negative emission technologies. This study builds on the promising moisture-swing modality for direct air capture of carbon dioxide by investigating the use of several new anions─orthosilicate, borate, pyrophosphate, tripolyphosphate, and dibasic phosphate─that when introduced into ion-exchange resins allow for the cyclable capture of CO2 under dry conditions and its release under wet conditions. These ions, as well as many others that failed to show moisture-swing performance, are tested and directly compared thermodynamically and kinetically to understand their differences. This includes the use of analytical approaches new to the carbon capture field, such as the correlation of adsorption isotherms to moisture-swing performance, the use of phase lag kinetics, the examination of the humidity-carbon capture hysteresis of the sorbents, and the precise quantification of ion loading using inductively coupled plasma-optical emission spectroscopy. Phosphate dibasic was found to have the largest mass-normalized CO2 moisture-swing capacity, whereas phosphate tribasic had the best performance when factoring in kinetics, and pyrophosphate had the highest swing capacity when normalizing on a per-ion or per-unit-charge basis. This work not only sheds light on ways to improve DAC but also provides insights pertinent to the advancement of gas separation, negative emission technologies, and sorbent materials.

Techno-economic and life cycle assessment of the integration of bioenergy with carbon capture and storage in the polygeneration system (BECCS-PS) for producing green electricity and methanol

Bioenergy with carbon capture and storage (BECCS) has the potential to produce negative emissions. This study assessed the overall energy efficiency and carbon dioxide (CO2) avoidance costs and emission footprint following the integration of BECCS with a polygeneration system (BECCS-PS) for the co-production of green electricity and methanol. The process was simulated in Aspen Plus and Aspen HYSYS v.11. Oil palm empty fruit bunches were used as the feed in a biomass integrated gasification combined cycle power plant. The flue gas, which contained CO2, was captured for methanol synthesis and carbon storage. Green hydrogen for use in methanol synthesis was produced through proton exchange membrane (PEM) electrolysis powered by solar PV (PV-PEM) and geothermal power with double-flash technology (GEO-PEM). The environmental impacts of the process were investigated by a life cycle assessment and the economic aspects were evaluated using the levelized cost method. The overall system efficiency was higher in the PV-PEM scenario than in the GEO-PEM scenario. For any production capacities, the green electricity generated from the BECCS-PS plant resulted in negative emissions. A biomass power plant with a low production capacity generated higher production and CO2 avoidance costs than that with a larger production capacity. The CO2 − eq emissions and costs for methanol production in the PV-PEM scenario were larger than those in the GEO-PEM scenario, with values of -0.83 to -0.70 kg CO2 − eq/kg MeOH and 1,191–1,237 USD/ton, respectively. The corresponding values were − 1.65 to -1.52 kg CO2 − eq/kg MeOH and 918–961 USD/ton, respectively, for the GEO-PEM scenario.Graphical

Biochar and Its Potential to Deliver Negative Emissions and Better Soil Quality in Europe

AbstractNegative emissions are essential to limit global warming, but their large‐scale deployment rises sustainability concerns. At the same time, agricultural soils are under increasing threat of degradation, as measured by losses in soil organic matter, water holding capacity, and nutrient retention, with increasing negative effects on plant productivity. Biochar from biomass residues is a technically mature option that does not compete for land and can typically restore key functions of degraded soils while delivering negative emissions. However, quantitative estimates of its potentials in Europe and a detailed spatially‐explicit analysis of the co‐benefits and trade‐offs for agricultural land are unclear. Here, we estimate an annual negative emission potential of biochar from forest and crop residues available in Europe from 1.7% to 3.9% of 2021s European greenhouse gas emissions (15.2%–35% of the agricultural emissions), depending on residue potentials and biochar scenarios. At the same time, biochar application to cropland increases water holding capacity (+6.5%‐9%), crop production (+7.1%‐8.4%), NH3 volatilization (+21.7%‐24.2%), and reduces soil N2O emissions (−13.7%–34.7%) and nitrogen leaching (−17.5%–22.7%). There are spatially heterogeneous trade‐offs for some soil effects (ammonia volatilization and yields) and air pollution (mainly due to emissions from biochar systems). Biochar offers synergistic solutions that co‐deliver across different sustainability challenges, but its optimal deployment requires strategies tailored to local conditions.

Direct evidence for atmospheric carbon dioxide removal via enhanced weathering in cropland soil

Enhanced weathering of soil-applied crushed silicate rocks may remove substantial atmospheric carbon dioxide; however, field testing of this negative emission technology is lacking. Models have suggested that enhanced weathering could, in principle, remove billions of tons of CO2 each year across global croplands, but methodological limitations have hindered direct measurement of CO2 sequestration via crushed rock amendments in agriculture. Further questions remain concerning the efficacy of this technology in arid climates. Here we provide direct evidence of rapid CO2 removal via enhanced weathering in soil pore water samples from a corn (Zea mays L.) cropping system in California. From December through February, during an extreme drought in our study region, we demonstrate a 2.6 to 2.9-fold increase in in situ bicarbonate alkalinity in response to additions of metabasalt and olivine fines. We provide a field analysis of carbon removal via silicate rock amendments and suggest enhanced weathering can remove carbon dioxide even under moisture-limited conditions.