Spatially Mapping the CO2 Alkaline Sorbent Diffuse Microenvironment Using Operando Raman Spectroscopy.

Scenarios for meeting ambitious climate targets rely on large-scale deployment of negative emissions technologies (NETs), including direct air capture (DAC). However, the tradeoffs between food, water and energy created by deploying different NETs are unclear. Here we show that DAC could provide up to 3 GtCO2 yr−1 of negative emissions by 2035—equivalent to 7% of 2019 global CO2 emissions—based on current-day assumptions regarding price and performance. DAC in particular could exacerbate demand for energy and water, yet it would avoid the most severe market-mediated effects of land-use competition from bioenergy with carbon capture and storage and afforestation. This could result in staple food crop prices rising by approximately fivefold relative to 2010 levels in many parts of the Global South, raising equity concerns about the deployment of NETs. These results highlight that delays in aggressive global mitigation action greatly increase the requirement for DAC to meet climate targets, and correspondingly, energy and water impacts. Negative emissions technologies are essential in scenarios for meeting Paris climate targets. Modelling results show that direct air capture could play an important role with less demand for land yet high energy and water use compared with BECCS and afforestation.

Amino acids make up a promising family of molecules capable of direct air capture (DAC) of CO2 from the atmosphere. Under alkaline conditions, CO2 reacts with the anionic form of an amino acid to produce carbamates and deactivated zwitterionic amino acids. The presence of the various species of amino acids and reactive intermediates can have a significant effect on DAC chemistry, the role of which is poorly understood. In this study, all-atom molecular dynamics (MD) based computational simulations and vibrational sum frequency generation (vSFG) spectroscopy studies were conducted to understand the role of competitive interactions at the air-aqueous interface in the context of DAC. We find that the presence of potassium bicarbonate ions, in combination with the anionic and zwitterionic forms of amino acids, induces concentration and charge gradients at the interface, generating a layered molecular arrangement that changes under pre- and post-DAC conditions. In parallel, an enhancement in the surface activity of both anionic and zwitterionic forms of amino acids is observed, which is attributed to enhanced interfacial stability and favorable intermolecular interactions between the adsorbed amino acids in their anionic and zwitterionic forms. The collective influence of these competitive interactions, along with the resulting interfacial heterogeneity, may in turn affect subsequent capture reactions and associated rates. These effects underscore the need to consider dynamic changes in interfacial chemical makeup to enhance DAC efficiency and to develop successful negative emission and storage technologies.

Direct air capture (DAC) is an emerging negative CO2 emission technology that aims to introduce a feasible method for CO2 capture from the atmosphere. Unlike carbon capture from point sources, which deals with flue gas at high CO2 concentrations, carbon capture directly from the atmosphere has proved difficult due to the low CO2 concentration in ambient air. Current DAC technologies mainly consider sorbent-based systems; however, membrane technology can be considered a promising DAC approach since it provides several advantages, e.g., lower energy and operational costs, less environmental footprint, and more potential for small-scale ubiquitous installations. Several recent advancements in validating the feasibility of highly permeable gas separation membrane fabrication and system design show that membrane-based direct air capture (m-DAC) could be a complementary approach to sorbent-based DAC, e.g., as part of a hybrid system design that incorporates other DAC technologies (e.g., solvent or sorbent-based DAC). In this article, the ongoing research and DAC application attempts via membrane separation have been reviewed. The reported membrane materials that could potentially be used for m-DAC are summarized. In addition, the future direction of m-DAC development is discussed, which could provide perspective and encourage new researchers' further work in the field of m-DAC.

Carbon capture and utilization (CCU) and carbon dioxide removal (CDR) technologies have the potential to significantly contribute to GHG reduction. Numerous studies have evaluated the CO2 reduction effects and economics of CCUs and CDRs; however, uncertainties in these evaluations due to various regional characterizations and future technological transitions are of high importance. In this study, four synthetic fuels (fuels produced from captured CO2 and H2), methanol, methane, gasoline, and diesel, were evaluated by life cycle assessment (LCA) and techno-economic assessment (TEA). Five representative countries with different regional characteristics were selected for the study. A bottom-up integrated LCA/TEA approach was used, involving detailed process simulations to avoid uncertainties and to evaluate future technological transitions based on direct air capture (DAC) and renewable energy. The overarching objective of this study was to provide a transparent framework with a common dataset generation methodology to determine the countries that have the advantages/disadvantages in synthetic fuel production and sale, considering the local operational parameters and large-scale introduction of DAC/renewable energy. Such multiple synthetic fuel analyses across various jurisdictions have not been conducted in previous studies. The results showed that the highest and lowest CO2 reductions were achieved by diesel (average 6.33 kg-CO2·kg−1) and methanol (average 3.43 kg-CO2·kg−1), respectively, whereas the highest and lowest product costs were of gasoline (average 2.96 USD·kg−1) and methanol (average 0.82 USD·kg−1), respectively. The technological transition using DAC and renewable energy showed average CO2 emission reductions of 47% (methanol), 99% (methane), 545% (gasoline), and 621% (diesel). Moreover, in the future, the lowest CO2 emission reduction costs are expected in Germany for methanol and diesel, Australia for methane, and Canada for gasoline. These findings can contribute to improving international collaboration to promote CCU and CDR technologies.

The direct air capture (DAC) of CO2 using aqueous solvents is plagued by slow kinetics and interfacial barriers that limit effectiveness in combating climate change. Functionalizing air/aqueous surfaces with charged amphiphiles shows promise in accelerating DAC; however, insight into these interfaces and how they evolve in time remains poorly understood. Specifically, competitive ion interactions between DAC reagents and reaction products feedback onto the interfacial structure, thereby modulating interfacial chemical composition and overall function. In this work, we probe the role of glycine amino acid anions (Gly-), an effective CO2 capture reagent, that promotes the organization of cationic oligomers at air/aqueous interfaces. These surfaces are probed with vibrational sum frequency generation spectroscopy and molecular dynamics simulations. Our findings demonstrate that the competition for surface sites between Gly- and captured carbonaceous anions (HCO3-, CO32-, carbamates) drives changes in surface hydration, which in turn tunes oligomer ordering. This phenomenon is related to a hierarchical ordering of anions at the surface that are electrostatically attracted to the surface and their ability to compete for interfacial water. These results point to new ways to tune interfaces for DAC via stratification of ions based on relative surface propensities and specific ion effects.

Direct air capture, the chemical removal of CO2 directly from the atmosphere, may play a role in mitigating future climate risk or form the basis of a sustainable transportation infrastructure. The current discussion is centered on the estimated cost of the technology and its link to "overshoot" trajectories, where atmospheric CO2 levels are actively reduced later in the century. The American Physical Society (APS) published a report, later updated, estimating the cost of a one million tonne CO2 per year air capture facility constructed today that highlights several fundamental concepts of chemical air capture. These fundamentals are viewed through the lens of a chemical process that cycles between removing CO2 from the air and releasing the absorbed CO2 in concentrated form. This work builds on the APS report to investigate the effect of modifications to the air capture system based on suggestions in the report and subsequent publications. The work shows that reduced carbon electricity and plastic packing materials (for the contactor) may have significant effects on the overall price, reducing the APS estimate from $610 to $309/tCO2 avoided. Such a reduction does not challenge postcombustion capture from point sources, estimated at $80/tCO2, but does make air capture a feasible alternative for the transportation sector and a potential negative emissions technology. Furthermore, air capture represents atmospheric reductions rather than simply avoided emissions.

The world is increasingly facing the direct effects of climate change triggering warnings of a crisis for the healthy existence of humankind. The dominant driver of the climate emergency is the historical and continued accumulation of atmospheric CO2 altering net radiative forcing on the planet. To address this global issue, understanding the core chemistry of CO2 manipulation in the atmosphere and proximally in the oceans is crucial, to offer a direct partial solution for emissions handling through negative emissions technologies. Many technologies have been proposed to develop a strategic and economic solution for carbon capture, storage, and utilization. In this paper, we review recent advances in technologies proposed for carbon capture and release via electrochemical process for point source/flue gas, direct air capture (DAC), and ocean/seawater capture. Electrochemical approaches to carbon capture are favorable in terms of reaction conditions, their ability to be incorporated into transformation processes, modularity, low relative carbon footprint, and compatibility with the availability of renewable electricity sources. We offer a critical comparative analysis of land- and ocean-based capture technologies to help guide future research and innovation.

Carbon Dioxide Removal (CDR) technologies have transitioned from a marginal concept to a central pillar of international climate mitigation scenarios, most notably those of the Intergovernmental Panel on Climate Change (IPCC) that limit global warming to 1.5°C. While these technologies promise to counterbalance hard-to-abate emissions and potentially restore atmospheric CO₂ levels, their rapid ascendancy warrants critical social scientific scrutiny. This article argues that CDR possesses a fundamental duality: it is simultaneously a potentially indispensable climate solution and a powerful vector for the reproduction of structural inequalities. Through a systematic, interdisciplinary analysis bridging energy justice and political ecology frameworks, we deconstruct this duality. The article first provides a typology of CDR approaches, from nature-based solutions like Afforestation/Reforestation (AR) to more technologically complex methods like Direct Air Capture with Carbon Storage (DACCS) and Bioenergy with Carbon Capture and Storage (BECCS). It then analyzes the socio-political dimensions of CDR deployment, focusing on three core axes of potential injustice: (1) the distributional inequities in the siting of projects and their localized environmental, land, and resource impacts; (2) the procedural injustices in decision-making processes that often exclude marginalized communities; and (3) the recognitional injustices that arise when CDR overlooks diverse forms of knowledge, values, and worldviews. The analysis reveals that without deliberate and transformative governance, the large-scale deployment of CDR risks reinforcing existing global and local power hierarchies, creating new "sacrifice zones," and diverting attention and resources from urgent decarbonization of energy systems. The article concludes that a just CDR pathway is not inevitable but must be actively constructed through anticipatory, participatory, and equity-centered policies that prioritize frontline communities, address root causes of inequality, and subordinate CDR to a overarching strategy of rapid emissions reduction.

Negative Emissions Technologies (NETs) will be needed in order to achieve the net zero emissions targets being set by many countries. These technologies will offset the residual greenhouse gas emissions of sectors that are inherently difficult to decarbonize. NETs draw down carbon through different physical, chemical, or biological pathways, and transfer it for storage to other environmental compartments. Examples of these techniques include afforestation, Biochar application, BioEnergy with Carbon Capture and Storage (BECCS), enhanced weathering, and Direct Air Capture (DAC). The large-scale deployment of NETs will be constrained by the footprints they apply to limited resources such as land, water, energy, and nutrients. In this work, a superstructure-based Linear Programming (LP) model is developed to optimize the carbon drawdown of integrated NET deployment under resource constraints. Results show that varying the target negative emissions and resource constraints affect the NETs portfolio and total cost.

A novel contactor for reducing the cost of direct air capture of CO2

Pathways for achieving the 1.5–2 °C global temperature moderation target imply a massive scaling of carbon dioxide (CO2) removal technologies, in particular in the 2040s and onwards. CO2 direct air capture (DAC) is among the most promising negative emission technologies (NETs). The energy demands for low-temperature solid-sorbent DAC are mainly heat at around 100 °C and electricity, which lead to sustainably operated DAC systems based on low-cost renewable electricity and heat pumps for the heat supply. This analysis is carried out for the case of the Maghreb region, which enjoys abundantly available low-cost renewable energy resources. The energy transition results for the Maghreb region lead to a solar photovoltaic (PV)-dominated energy supply with some wind energy contribution. DAC systems will need the same energy supply structure. The research investigates the levelised cost of CO2 DAC (LCOD) in high spatial resolution and is based on full hourly modelling for the Maghreb region. The key results are LCOD of about 55 €/tCO2 in 2050 with a further cost reduction potential of up to 50%. The area demand is considered and concluded to be negligible. Major conclusions for CO2 removal as a new energy sector are drawn. Key options for a global climate change mitigation strategy are first an energy transition towards renewable energy and second NETs for achieving the targets of the Paris Agreement.

This paper explores the role of negative emissions technologies (NETs) in energy systems, bioenergy with carbon capture and storage (BECCS) and direct air capture (DAC) with geological carbon storage (DACCS) in particular, using a bottom-up energy system model TIMES-Japan that participated in the 35th study of the Stanford Energy Modeling Forum (EMF 35 JMIP) focusing on the energy transitions for the long-run climate goals. Modeling results show that large-scale deployment of NETs is essential to achieve the net-zero vision of Japan’s long-term strategy, however, these NETs might not be enough in the case of the highest energy service demands. Within the feasible solution space, earlier deployment of BECCS with domestic biomass can contribute effectively to achieve the target with the support of the DACCS at the later period if both technologies are available. It shows feasible results without DACCS only in the lowest energy service demands, implying the importance of urgent research, development, and deployment of DACCS. Furthermore, this study shows that earlier deployment of DAC system with CO2 utilization in fuel production is a cost-effective way to lead the large-scale deployment of the DAC as NETs.

Introduction Integration of Carbon Dioxide Removal (CDR) into existing climate change mitigation policy frameworks has begun. A broad set of policy instruments is available for the development and deployment of CDR technologies. While current discussions emphasize carbon markets to scale CDR, other non-market based policy instruments could play an important role. This article examines several non-market policy instruments through a new CDR-specific assessment framework across four dimensions: feasibility, climate effectiveness, impacts on individuals and society, and the ratio and distribution of impacts. Four theoretical scenarios, heterogeneous in assumed time horizon, spatial coverage, and utilized non-market policy instrument, are evaluated: (1) a technology-specific Carbon Contract for Difference in the EU; (2) an internationally funded capacity-building campaign for Brazilian farmers to utilize voluntary carbon markets; (3) a global carbon takeback obligation for fossil fuel producers; and (4) a national corporate tax exemption for Direct Air Capture (DAC) plant setup and operation. Discussion The assessment finds that no single policy instrument performs strongly across all four dimensions. This suggests that the prioritization of policy instruments for CDR depends on how decision-makers weigh the assessed dimensions. Different stakeholder objectives will lead to different weighing of dimensions and, thus, rankings of policy instruments. Conclusion Careful and transparent policy design process that reflects local contexts and national conditions is essential to ensure robust and stable decisions supported by a critical mass of stakeholders. A nuanced, inclusive approach can facilitate the implementation of a complementary suite of policy instruments that underpin responsible and effective global collaboration on CDR.

Currently, scientists and investors consider Direct Air Capture (DAC) as one of the candidates to reduce CO2 emissions. The emissions cut is pressing since 30% of the current greenhouse gas emissions must be addressed by 2030. In seven years, CO2 removal (CDR) technologies are expected to reach a Technology Readiness Level (TRL), relevant to industrial applications. The most promising technologies are at TRL-7, but the jump to TRL-11 in the new IEA scale for disruptive technologies looks unlikely because the scale-up from small pilots to industrial scale requires time and large investments. Moreover, validation on a large scale is still missing or even unplanned. This work also identifies the critical materials supply chain and the competition with the energy transition as limiting factors which could further hinder DAC deployment and reduce DAC contribution in the next years when a first significant emissions cut should be addressed.

Direct air capture (DAC), as a complementary strategy to carbon capture and storage (CCS), offers a scalable and sustainable pathway to remove CO2 directly from the ambient air. This study presents a detailed evaluation of the amine-functionalised metal-organic framework (MOF) sorbent, mmen-Mg2(dobpdc), for DAC using a temperature–vacuum swing adsorption (TVSA) process. While this sorbent has demonstrated promising performance in point-source CO2 capture, this is the first dynamic simulation-based study to rigorously assess its effectiveness for low-concentration atmospheric CO2 removal. A transient one-dimensional TVSA model was developed in Aspen Adsorption and validated against experimental breakthrough data to ensure accuracy in capturing both the sharp and gradual adsorption kinetics. To enhance process efficiency and sustainability, this work provides a comprehensive parametric analysis of key operational factors, including air flow rate, temperature, adsorption/desorption durations, vacuum pressure, and heat exchanger temperature, on process performance, including CO2 purity, recovery, productivity, and specific energy consumption. Under optimal conditions for this sorbent (vacuum pressure lower than 0.15 bar and feed temperature below 15 °C), the TVSA process achieved ~98% CO2 purity, recovery over 70%, and specific energy consumption of about 3.5 MJ/KgCO2. These findings demonstrate that mmen-Mg2(dobpdc) can achieve performance comparable to benchmark DAC sorbents in terms of CO2 purity and recovery, underscoring its potential for scalable DAC applications. This work advances the development of energy-efficient carbon removal technologies and highlights the value of step-shape isotherm adsorbents in supporting global carbon-neutrality goals.