What is carbon capture & use?
Carbon capture & use (CCU), sometimes called carbon utilization or carbon-to-value, involves capturing carbon dioxide (CO2) and using it in economically beneficial ways. This covers a wide range of activities, from converting CO2 into useful products to injecting CO2 into depleted oil reservoirs for enhanced oil recovery. CCU remains an area of active technological development, with companies experimenting with using captured CO2 to create products as varied as synthetic jet fuel, fish food, and carbon-negative concrete, to name just a few.
Is carbon capture & use a type of carbon removal?
Processes that capture CO2 from the atmosphere and turn it in long-lived products, such as cement or building insulation, count as carbon removal because they reduce atmospheric CO2 levels over the long run. Processes that capture CO2 from the atmosphere and use it in short-lived products, such as beverages or biodegradable plastics or synthetic fuel, do not count as carbon removal because the carbon they capture soon returns to the atmosphere. They amount to “carbon recycling.” Processes that only capture CO2 from fossil fuel consumption do not count as carbon removal, regardless of what they do with the carbon, because they are not removing CO2 that is already in the atmosphere. Enhanced oil recovery could, in theory, count as a form of carbon removal under very specific circumstances, but even when the CO2 injected underground has been captured from the air, burning the oil that is pumped out of the well will usually create more CO2 than the process initially sequestered.
The role of carbon capture & use in climate policy
Different kinds of CCU can play very different roles in climate policy. Carbon-negative CCU, which takes carbon from the air and embeds it in long-lasting products, could compensate for emissions from harder-to-abate sectors or help reduce atmospheric concentrations of CO2 by drawing CO2 out of the atmosphere. Carbon recycling is carbon neutral, at best, but certain kinds could reduce emissions by displacing fossil fuels. Synthetic fuels, in particular, could play a role in decarbonizing sectors like aviation. “Fossil CCU,” meaning CCU that captures and uses CO2 from coal or gas power plants, could help finance carbon capture technology on such plants, which would significantly reduce their emissions. In all three cases, the challenge is scaling up CCU to capture and use millions or billions of tonnes of CO2 per year. Unless and until that happens, CCU will not make a meaningful contribution to climate policy, though there may be other reasons to pursue certain types of CCU.
Point-source carbon capture, which could be attached to fossil fuel plants, bioenergy plants, or industrial facilities, is well-developed, but for financial reasons, it is not yet widely deployed. New methods of capturing carbon are emerging, including methods for capturing CO2 from the air. While there are some mature technologies for using captured CO2, such as enhanced oil recovery and greenhouse enrichment, many new technologies for using captured CO2 are under active research and development. Of these, low-carbon and carbon-negative building materials currently appear to have the biggest carbon removal potential because of the scale of the building industry and the durability of carbon storage in building materials.
- Life cycle accounting: sound methods of accounting for the life-cycle emissions of CCU processes are needed to identify genuinely carbon-neutral or carbon-negative CCU processes
- End-of-life handling of products: institutions and processes need to be developed to ensure that the carbon in long-lived products is not released to the atmosphere at the end of the product’s lifespan
- Monitoring, reporting, and verification: robust mechanisms are needed for monitoring, reporting, and verifying that carbon has been captured and stored
- National Academies of Sciences, Engineering, and Medicine. 2019. Gaseous Carbon Waste Streams Utilization: Status and Research Needs. Washington, DC: National Academies Press.
- Global CO2 Initiative. 2016. Global Roadmap for Implementing CO2 Utilization. University of Michigan.
- McGlade, C. 2019. “Can CO2-EOR really provide carbon-negative oil?” International Energy Agency. https://www.iea.org/commentaries/can-co2-eor-really-provide-carbon-negative-oil