“A process in which carbon dioxide (CO2) is captured and the carbon then used in a product. The climate effect of CCU depends on the product lifetime, the product it displaces, and the CO2 source (fossil, biomass or atmosphere)” (IPCC AR6 WGIII). There are a range of applications for captured CO2 – it can be used directly in greenhouses or in beverages, or as a chemical feedstock in the manufacture of new products like fuels and chemicals. Injection of CO2 into concrete is an emerging application.
CCU take place in different ways, with different options for both capture and end use available.
- Capture – CO2 can be captured at either a point source or from the atmosphere, as with direct air capture.
- Use of CO2 – CO2 can be used in shorter- and longer-lived products. Shorter lived products like fuels and chemicals will lead to the re-release of CO2 back to the atmosphere (for example when fuels are combusted or chemicals reacted). But longer-lived products, like cementitious building materials, could keep CO2 out of the atmosphere for climate-relevant timescales.
Given these different processes for CCU, different climate benefits will arise – in some cases emissions reduction, in some cases removal. If point source capture is combined with shorter-lived products, CCU can limit the need for additional fossil fuel extraction to make those products, thereby reducing emissions. If atmospheric capture is combined with sufficiently long-lived products, such activity can be considered as CDR. In all cases, this of course also depends on the emissions released in the lifecycle of the process.