Direct air capture (DAC) can provide an impactful, engineered approach to combat climate change by removing carbon dioxide (CO2) from the air. However, to meet climate goals, DAC needs to be scaled at a rapid rate. Current DAC approaches use engineered contactors filled with chemicals to repeatedly capture CO2 from the air and release high purity CO2 that can be stored or otherwise used. This review article focuses on two distinctive, commercial DAC processes to bind with CO2: solid sorbents and liquid solvents. We discuss the properties of solvents and sorbents, including mass transfer, heat transfer and chemical kinetics, as well as how these properties influence the design and cost of the DAC process. Further, we provide a novel overview of the considerations for deploying these DAC technologies, including concepts for learning-by-doing that may drive down costs and material requirements for scaling up DAC technologies.

A review of direct air capture (DAC): scaling up commercial technologies and innovating for the future

Recent IPCC assessments highlight a key role for large‐scale carbon removal in meeting the objectives of the Paris Agreement. This focus on removal, also referred to as negative emissions, is suggestive of novel opportunities, risks, and challenges in addressing climate change, but tends to build on the narrow techno‐economic framings that characterize integrated assessment modeling. While the discussion on negative emissions bears important parallels to a wider and older literature on carbon sequestration and carbon sinks, this earlier scholarship—particularly from the critical social sciences—is seldom engaged with by the negative emissions research community. In this article, we survey this “long history” of carbon removal and seek to draw out lessons for ongoing research and the emerging public debate on negative emissions. We argue that research and policy on negative emissions should proceed not just from projections of the future, but also from an acknowledgement of past controversies, successes and failures. In particular, our review calls attention to the irreducibly political character of carbon removal imaginaries and accounting practices and urges acknowledgement of past experiences with the implementation of (small‐scale) carbon sequestration projects. Our review in this way highlights the importance of seeing continuity in the carbon removal discussion and calls for more engagement with existing social science scholarship on the subject. Acknowledging continuity and embracing an interdisciplinary research agenda on carbon removal are important aspects in making climate change mitigation research more responsible, and a precondition to avoid repeating past mistakes and failures. This article is categorized under: The Carbon Economy and Climate Mitigation > Benefits of Mitigation

https://onlinelibrary.wiley.com/doi/pdf/10.1002/wcc.671

Negative emissions and the long history of carbon removal

With the proposal to achieve carbon neutrality by the mid-21st century, carbon capture, utilization, and storage (CCUS) as a critical negative carbon technology is receiving extensive attention and concerns around the world. Under this context, the development of CCUS and relevant literature both have been experiencing an upsurge. However, the actual scale of CCUS is still far behind our expectations, especially, the various risks and uncertainties associated with its deployment planning have not yet been addressed clearly. Therefore, this paper provides an overview of model-based CCUS deployment pathways toward carbon neutrality, as well as the associated risks of financial, technical, environmental, health and safety (EHS) aspects. On this basis, we scrutinize the potential challenges that could lead to the pace of CCUS deployment inconsistent with the need to achieve a carbon-neutral target. The results suggest that the “Golden Age” of CCUS deployment lies from 2040 to 2060 in the world, while 2030–2050 for China. Furthermore, we found that inadequate exploration in geologic storage capacity also creates a critical conundrum for CCUS deployment and optimization, apart from typical challenges including high failure rate of projects, the lack of financial support and market stimulus, as well as incomplete regulation framework and risk-sharing mechanism. Lastly, this paper points out the further potential research direction, followed by policy implications and recommendations. • A comprehensive reference for CCUS deployment towards carbon neutrality is presented. • We discuss possible risks or uncertain factors for altering CCUS deployment paths and planning layout. • Future needs to improve geological storage exploration and estimation are highlighted. Further potential research direction and policy implications for CCUS are provided. 

A critical review on deployment planning and risk analysis of carbon capture, utilization, and storage (CCUS) toward carbon neutrality

Bioenergy with Carbon Capture and Storage (BECCS) is a Carbon Dioxide Removal (CDR) technology that will likely be necessary to reach global net-zero carbon dioxide emission goals. In order to assess the European BECCS potential, we quantify at 1 km resolution the technical potential for biogenic CDR considering seven different BECCS configurations that do not require purpose-grown bio-energy plantations. Combining process engineering with geospatial assessment, we find that up to 5% of 2018 European emissions, or about 200 million tons CO2 per year, could be mitigated with biogenic CDR from BECCS. Such potential is at the lower bound of the range of projected CDR needs for Europe. Two thirds of this potential is from existing point sources (pulp and paper, biomass co-fired, waste-to-energy, and wastewater treatment facilities), while one third is from distributed sources (crop residues, organic food waste, and livestock manure). From a geopolitical perspective, only a few European countries reach or exceed their CDR needs via BECCS. Those countries, which will not be able to reach carbon-neutrality with domestic biomass resources, will likely need to resort to other CDR strategies or import biomass from abroad. From a geographic perspective, distances from emission sources and storage sites are rather unfavourably distributed. Based on our quantitative assessment we conclude that: (1) tapping into the whole 200 million tons CO2 per year will be challenging because of the unfavourable source–sink distance distribution; (2) there is a need for more and better distributed prospective CO2 storage sites in Europe; and (3) the mobilization of these large amounts of CO2 will require the realization of a Europe-wide CO2 transportation network.

/pdf/assessment-of-carbon-dioxide-removal-potential-via-beccs-in-3py4akrl4g.pdf

Assessment of carbon dioxide removal potential via BECCS in a carbon-neutral Europe

Significant progress has been made in direct air capture (DAC) in recent years. Evidence suggests that the large-scale deployment of DAC by adsorption would be technically feasible for gigatons of CO2 capture annually. However, great efforts in adsorption-based DAC technologies are still required. This review provides an exhaustive description of materials development, adsorbent shaping, in situ characterization, adsorption mechanism simulation, process design, system integration, and techno-economic analysis of adsorption-based DAC over the past five years; and in terms of adsorbent development, affordable DAC adsorbents such as amine-containing porous materials with large CO2 adsorption capacities, fast kinetics, high selectivity, and long-term stability under ultra-low CO2 concentration and humid conditions. It is also critically important to develop efficient DAC adsorptive processes. Research and development in structured adsorbents that operate at low-temperature with excellent CO2 adsorption capacities and kinetics, novel gas-solid contactors with low heat and mass transfer resistances, and energy-efficient regeneration methods using heat, vacuum, and steam purge is needed to commercialize adsorption-based DAC. The synergy between DAC and carbon capture technologies for point sources can help in mitigating climate change effects in the long-term. Further investigations into DAC applications in the aviation, agriculture, energy, and chemical industries are required as well. This work benefits researchers concerned about global energy and environmental issues, and delivers perspective views for further deployment of negative-emission technologies.

Recent advances in direct air capture by adsorption.

Getting to Neutral: Options for Negative Carbon Emissions in California

The value of CCUS in transitions to net-zero emissions

Cutting through the noise on negative emissions

California’s Low Carbon Fuel Standard (LCFS) is one of the most important policies to develop and deploy low-carbon and carbon-negative fuels. Yet, because the LCFS is designed to deliver the lowest-cost carbon intensity (CI) reductions possible in the transportation fuel system, it may fail to deliver technologies that would be poised to offer deeper decarbonization or other ancillary benefits to California’s people and environment. We contemplate administrative changes to the LCFS to further stimulate the commercialization of promising low-carbon and carbon-negative fuels. To do so, we examine promising technical pathways, their barriers to commercialization, and recent administrative actions by the CA Air Resources Board (ARB) under the LCFS to promote novel lower-carbon fuels. We propose three actions that ARB could undertake to promote commercialization within existing authorities. To commercialize low-carbon and carbon negative fuel, including those derived from forest residue feedstocks, ARB could: 1) embrace the most up-to-date science regarding lifecycle greenhouse gas emissions, 2) create additional, targeted incentives for very low-carbon or carbon-negative fuels through a volumetric technology carve-out or credit multiplier, and 3) ensure that the LCFS stimulates the best-performing fuels across a variety of sustainability parameters.

/pdf/policy-options-for-deep-decarbonization-and-wood-utilization-5jlmz2v7qg.pdf

Policy Options for Deep Decarbonization and Wood Utilization in California's Low Carbon Fuel Standard

Integrated assessment and other macro-scale energy systems models are valuable tools for exploring alternate ways (scenarios) to decarbonize an economy. A shortcoming, however, is that most models assume new mitigation...

https://pubs.rsc.org/en/content/articlepdf/2022/ee/d2ee01244h

Sam Uden

Papers

Getting to Neutral: Options for Negative Carbon Emissions in California

The value of CCUS in transitions to net-zero emissions

Cutting through the noise on negative emissions

Policy Options for Deep Decarbonization and Wood Utilization in California's Low Carbon Fuel Standard

Bridging capital discipline and energy scenarios