APS Releases Report on Atmospheric Carbon Dioxide Removal

Technologies hold promise, but come at a cost

Washington, DC – January 27, 2025 — Novel carbon dioxide removal (CDR) technologies are increasingly being considered as potentially useful tools to combat climate change. For specific atmospheric carbon dioxide management targets to be achieved, large-scale CDR strategies may be needed, even with aggressive efforts to reduce carbon dioxide emissions in the coming decades, according to a new report released by the American Physical Society (APS). The report is being simultaneously published in PRX Energy, APS’ journal featuring energy science and technology research, alongside an editorial exploring the study’s findings. A webinar and Q&A will be hosted by APS with the report's authors on Feb. 27 at 12 PM ET. You can register for the webinar and Q&A online.

The report breaks down the physical requirements necessary for large-scale implementation of CDR technologies, demonstrating the challenges inherent to incorporating CDR into any carbon dioxide management portfolio. It also provides a technical overview of new and current CDR approaches and evaluates their fundamental physical constraints. The study’s authors worked for more than a year and consulted with dozens of experts in academia, national labs, and industry. Additionally, independent experts reviewed the report before its publication.

“CDR has the potential to be a useful tool but it is imperative to develop a rational set of policies for atmospheric carbon management that can balance the costs and benefits of these technologies with those of efforts toward CO₂ emission reduction,” says Washington Taylor, MIT physicist and the lead author on the report.

APS released its report, “Atmospheric Carbon Dioxide Removal – A Physical Science Perspective,” following growing interest in both the public and private sectors regarding the feasibility of using CDR technologies to help tackle climate change. Various approaches to CDR use engineered or natural systems to extract carbon dioxide molecules from the air, aiming to sequester them underground or in other long-term storage. CDR technologies are different from carbon capture and storage technologies that remove carbon dioxide at a source such as a power plant or cement production facility.

The study notes that if CDR is to make a meaningful impact on global carbon dioxide levels, it would have to be scaled to annually remove billions of metric tons of carbon dioxide from the atmosphere. This would necessitate processing an amount of air greater than the total volume circulated through all global air conditioning and cooling systems each year. Existing implementations of CDR technologies currently operate at a level roughly one hundred thousand times lower than this estimated threshold for impact.

CDR technologies, according to the study, can be classified into two categories: cyclic systems where the same materials are used to capture carbon dioxide over and over, and once-through systems where a resource is used a single time to capture carbon dioxide.

Cyclic systems, such as chemical direct air capture, use large amounts of energy. The fundamental laws of physics dictate a minimum amount of energy required to process a given volume of air in these systems. For example, the minimum energy needed to remove one billion metric tons of carbon dioxide from the atmosphere would be comparable to the combined electric consumption of the entire state of Virginia in 2021. Current CDR technologies currently require several times more energy than the fundamental minimum. The upside for these cyclic systems: they are expected to have less environmental impact than other CDR technologies, and their effectiveness can be easier to verify.

Once-through CDR systems, such as enhanced rock weathering – which require mining and grinding large amounts of rocks that will absorb carbon dioxide out of the air — involve less energy, but have uncertain effectiveness and may have a substantially larger environmental impact.

Ecosystem-based approaches, which can be both cyclic or once-through, such as reforestation and other changes in land use practices, are currently the primary methods that actively provide CDR. These approaches use energy from sunlight and natural inputs such as water. While ecosystem-based methods provide inexpensive ways to achieve some CDR, their potential is limited, and it is challenging to ensure that the carbon remains locked away.

Additionally, the report points out that, unlike the exponential improvements seen in computer efficiency in the past decades, there is no prospect for such a growth in efficiency for CDR approaches, which face fundamental physical limits to their efficiency at scale.

Based on the technical overview, the report makes several recommendations for the U.S. federal government and industry. These include ensuring that the potential for CDR does not compromise ongoing actions to reduce carbon emissions. The report observes, however, that while large-scale CDR technologies require a lot of energy and material resources, they might be needed in combination with emission reduction strategies to achieve specific climate goals. Research and development on CDR should be selectively pursued, despite the many challenges described in the report.

Additionally, when considering CDR technologies at scale, the report recommends that policymakers and industry should:

• Explore and implement ecosystem-based CDR approaches that leverage natural processes without compromising essential needs like food security.
• Incorporate carbon-free power sources into plans for future CDR facilities, and carefully assess land or sea area requirements for large-scale CDR deployment.
• Exercise caution in deploying once-through CDR approaches until their effectiveness and impact are thoroughly evaluated.
• Develop reliable systems for measurement, reporting, and verification to assess and compare different CDR approaches.
• Design and implement economic and policy frameworks to facilitate the cost-effective development and deployment of CDR and emission reduction strategies.

Authors of the 2025 APS report “Atmospheric Carbon Dioxide Removal – A Physical Science Perspective"

Learn more about the report's authors:

• Washington Taylor, professor of Physics at MIT and Director of MIT's Center for Theoretical Physics
• Robert Rosner, theoretical physicist and William E. Wrather Distinguished Service Professor at the University of Chicago
• Brad Marston, professor of physics at Brown University and director of the Brown Theoretical Physics Center
• Jonathan S. Wurtele, professor of physics at the University of California, Berkeley