Amine-Functionalized Activated Carbon Monoliths by 3D Printing for Direct Air Capture.

The potential of direct air capture using adsorbents in cold climates.

Direct air capture technologies have gained prominence as vital tools for atmospheric carbon dioxide removal, with four major categories, namely liquid solvent-based, solid sorbent-based, electrochemical, and emerging hybrid systems, demonstrating varying degrees of maturity and feasibility. Liquid solvent-based direct air capture, including systems using potassium hydroxide, amines, and advanced ionic liquids or deep eutectic solvents, benefits from high CO2 reactivity and established chemical regeneration processes, but faces limitations from high thermal energy demands, solvent degradation, and environmental handling concerns. Solid sorbent-based systems, such as those utilizing amine-functionalized materials or metal-organic frameworks, offer low-temperature regeneration and modular designs, yet often suffer from variable adsorption capacity under different humidity levels and degradation over multiple cycles. Electrochemical direct air capture is a rapidly advancing field that uses redox-active materials or ion-exchange membranes to reversibly bind and release CO2 using electrical energy. These systems enable operation under ambient conditions with high selectivity and reduced thermal input, though challenges persist in terms of redox material stability and scalability. Other emerging methods, such as cryogenic, photocatalytic, mineralization-based, and biological direct air capture, offer innovative pathways to reduce energy use or permanently sequester CO2, but remain at early developmental stages. While significant advances have improved energy efficiency, cost-effectiveness, and operational stability across direct air capture technologies, further research is needed to enhance long-term material performance, develop low-cost, scalable reactor designs, and improve integration with renewable energy systems. Future studies should prioritize techno-economic assessments, lifecycle analysis, and hybrid approaches that combine the strengths of multiple direct air capture pathways to achieve cost-effective and durable carbon removal at gigaton scales.

Misconceptions and myths surrounding “negative emissions”

Abstract. Post-combustion capture and direct air capture are two important processes for reducing CO2 content in the atmosphere and mitigating climate change. Post-combustion capture involves capturing CO2 emissions produced from power plants, while direct air capture removes CO2 directly from the ambient air. Gallate-based MOFs can offer remarkable CO2 adsorption capacity. However, there is scarcity of reported works related to N2 adsorption, limiting the scope of research on binary isotherms of CO2/N2 mixture. Therefore, this work aims to investigate the adsorption of pure N2 gas using gallate-based MOFs. Additionally, prediction of binary isotherms of CO2/N2 mixtures was carried out to assess the efficiency of these frameworks for post-combustion capture and direct air capture. The predicted binary isotherms of CO2/N2 mixture revealed that gallate- based MOFs hold potential as adsorbents for both post-combustion capture and direct air capture. The IAST selectivity illustrated that gallate-based MOFs possess the capability to selectively capture CO2 from CO2/N2 mixture, with Mg-gallate exhibiting the highest values, followed by Ni- gallate and Co-gallate. Therefore, Mg-gallate, Co-gallate and Ni-gallate can be suggested as promising adsorbents for post-combustion capture and direct air capture.

The urgency to address global climate change induced by greenhouse gas emissions is increasing. In particular, the rise in atmospheric CO2 levels is generating alarm. Technologies to remove CO2 from ambient air, or "direct air capture" (DAC), have recently demonstrated that they can contribute to "negative carbon emission." Recent advances in surface chemistry and material synthesis have resulted in new generations of CO2 sorbents, which may drive the future of DAC and its large-scale deployment. This Review describes major types of sorbents designed to capture CO2 from ambient air and they are categorized by the sorption mechanism: physisorption, chemisorption, and moisture-swing sorption.

Negative emissions technologies are gaining widespread acceptance as crucial tools in achieving climate goals, such as keeping global temperatures below 2 °C of pre-industrial levels by 2100. Two technologies central to carbon dioxide removal efforts are direct air capture and Bioenergy with carbon capture and storage. While both technologies have undergone extensive study, only a few studies have explored the potential of using biomass as an energy source for direct air capture technology. This is despite bioenergy with carbon capture having the ability to provide carbon-negative heat and power, as well as its potential impact on the climate mitigation goals of the century. This study aims to investigate the feasibility of meeting the energy requirements of a direct air capture unit using bioenergy. Combining these units will result in compounded negative emissions for the integrated system. The objective is to examine the thermal and electrical requirements of the two primary approaches used in direct air capture design: the liquid solvent and solid sorbent direct air capture units, and to calculate the compounded negative emissions achieved by integrating them with bioenergy. The results of this study demonstrate that for a direct air capture plant capturing 1 mega ton of carbon dioxide per year, approximately 1200 and 2400 tons of biomass per day would be sufficient to meet the energy needs of the solid sorbent and liquid solvent direct air capture systems, respectively. The combined capture efficiency of both types of direct air capture systems integrated with bioenergy stands at 91.19% to 93.9% with overall carbon captured up to 1.51 mega tons of carbon dioxide per year. Over the century, integrating bioenergy into direct air capture units can remove gigaton levels of carbon from the atmosphere without disrupting the demand–supply dynamics of existing and future energy systems.

Carbon capture and utilization: More than hiding CO2 for some time

Direct air capture is a negative emission technology that captures CO2 directly from the air. It is shown to be a promising tool for fighting climate change, yet still a work in progress. Direct Air Capture of CO2 provides an overview of this technology, starting with an overview in Chapter 1 of major climate change events, moving into a comprehensive review of negative emission technologies in Chapter 2, including direct air capture. Chapter 2 covers some of the challenges associated with direct air capture and the feasibility of utilizing such a process for large-scale applications. Chapter 3 presents a literature review of sorbents under investigation for direct air capture. The advantages and disadvantages of each approach for direct air capture are extracted from results published in the literature and are summarized along with areas of ongoing work. Parallel to ongoing research on developing high-performing sorbents for direct air capture, companies and startups have begun testing pilot to commercial scale direct air capture plants. Chapter 4 summarizes the efforts of such institutions. Global CO2 markets under development to construct commercialization pathways for direct air capture, such as enhanced oil recovery, synthetic fuels, cement, greenhouses, and food and beverages, are also reviewed in Chapter 4. The digital primer concludes with the authors’ view on the prospects of direct air capture technology for fighting climate change. Information provided in all chapters is carefully referenced to relevant literature so the reader may dive deeper into the details if interested. The authors hope this digital primer will bring inspiration and ideas to young scientists.

Model-based thermodynamic analysis of direct air capture units in repurposed power plant cooling towers

Direct air capture (DAC) is a carbon removal technology that selectively extracts CO2 from ambient air, where it exists at trace concentrations of approximately 400 ppm (0.04%), using chemical or physical separation processes. As the only CO2 capture approach capable of delivering negative net emissions, DAC has emerged as a critical CO2 removal (CDR) strategy for achieving global net-zero targets. However, its operation requires substantial electrical energy to drive large air flows and significant thermal energy for sorbent regeneration, which remains a major barrier to large-scale deployment. Coupling DAC with nuclear power has been proposed as a promising approach because nuclear systems can provide stable, carbon-free electricity and heat. This review summarizes recent studies on the integration of DAC with nuclear power plants and analyzes the current technological maturity of nuclear–DAC systems. In particular, the paper compares different DAC configurations, evaluates their energy requirements and integration strategies with nuclear heat and power sources, and identifies key technical and economic challenges for future deployment.

Current climate targets require negative carbon dioxide (CO2) emissions. Direct air capture is a promising negative emission technology, but energy and material demands lead to trade-offs with indirect emissions and other environmental impacts. Here, we show by life-cycle assessment that the commercial direct air capture plants in Hinwil and Hellisheiði operated by Climeworks can already achieve negative emissions today, with carbon capture efficiencies of 85.4% and 93.1%. The climate benefits of direct air capture, however, depend strongly on the energy source. When using low-carbon energy, as in Hellisheiði, adsorbent choice and plant construction become more important, inducing up to 45 and 15 gCO2e per kilogram CO2 captured, respectively. Large-scale deployment of direct air capture for 1% of the global annual CO2 emissions would not be limited by material and energy availability. However, the current small-scale production of amines for the adsorbent would need to be scaled up by more than an order of magnitude. Other environmental impacts would increase by less than 0.057% when using wind power and by up to 0.30% for the global electricity mix forecasted for 2050. Energy source and efficiency are essential for direct air capture to enable both negative emissions and low-carbon fuels. Direct air capture (DAC) of CO2 has garnered interest as a negative emissions technology to help achieve climate targets, but indirect emissions and other environmental impacts must be better understood. Here, Deutz and Bardow perform a life-cycle assessment of DAC plants operated by Climeworks, based on industrial data.

Textured carbon capture composite (C3) films for distributed direct air capture in urban spaces

Direct air capture (DAC) is critical for achieving stringent climate targets, yet the environmental implications of its large-scale deployment have not been evaluated in this context. Performing a prospective life cycle assessment for two promising technologies in a series of climate change mitigation scenarios, we find that electricity sector decarbonization and DAC technology improvements are both indispensable to avoid environmental problem-shifting. Decarbonizing the electricity sector improves the sequestration efficiency, but also increases the terrestrial ecotoxicity and metal depletion levels per tonne of CO2 sequestered via DAC. These increases can be reduced by improvements in DAC material and energy use efficiencies. DAC exhibits regional environmental impact variations, highlighting the importance of smart siting related to energy system planning and integration. DAC deployment aids the achievement of long-term climate targets, its environmental and climate performance however depend on sectoral mitigation actions, and thus should not suggest a relaxation of sectoral decarbonization targets.

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.

InnoSepra’s project, “Transformational Sorbent Materials for a Substantial Reduction in the Energy Requirement for Direct Air Capture of CO2,” utilized computational tools, materials characterization, and lab scale testing to optimize previously identified materials to determine their performance under direct air capture conditions. InnoSepra utilized the test results to determine the energy required for regeneration and to develop a high-level process design/analysis to demonstrate the application of developed materials for direct air capture which could be utilized for future techno-economic and life-cycle analyses to fully assess the potential of the materials for direct air capture. InnoSepra also updated the State Point Data Table and completed the environmental, health, and safety (EH&S) Risk Assessment. The overall objective of this project was to demonstrate that the proposed transformational materials can lead to a substantial reduction in the energy requirement for direct capture of carbon dioxide (CO2) from air compared to current state-of-the-art direct air capture processes. An assessment of the production of large quantities of the proposed materials was made for a potential future commercial implementation of these materials for direct air capture. The ultimate goals of the Project were to confirm the expected performance at the lab scale and to provide sufficient data to enable the development of a preliminary technical analysis to confirm the projected energy savings of at least 50% compared to current state-of-the-art technologies for direct air capture based on absorption and adsorption. During the project execution, InnoSepra demonstrated that Direct Air Capture with physical sorbents developed/identified during this project has the potential for a significant reduction in the energy required for capture and, when fully developed, the technology has the potential for an energy requirement below 4 GJ/MT of CO2. The starting TRL for major unit operations, moisture removal, and CO2 capture, was 2, and the end of the project TRL for these unit operations was 3-4. The technology uses near-commercial sorbents and the production of these materials for commercial-scale demonstration can be done in 2-3 years. The materials also have a long life (>5 years) and pose little or no EH&S issues.