Carbon Dioxide Removal

Carbon dioxide removal (CDR) methods refers to a number of technologies which reduce the levels of carbon dioxide in the atmosphere. Among such technologies are bio-energy with carbon capture and storage, biochar, direct air capture, ocean fertilization and enhanced weathering. CDR is a different approach than removing CO₂ from the stack emissions of large fossil fuel point sources, such as power stations. The latter reduces emission to the atmosphere but cannot reduce the amount of carbon dioxide already in the atmosphere. As CDR removes carbon dioxide from the atmosphere, it creates negative emissions, offsetting emissions from small and dispersed point sources such as domestic heating systems, airplanes and vehicle exhausts. It is regarded by some as a form of geoengineering, while other commentators regard it as a form of carbon capture and storage.

The likely need for CDR has been publicly expressed by a range of individuals and organizations involved with climate change issues, including IPCC chief Rajendra Pachauri, the UNFCCC executive secretary Christiana Figueres, and the World Watch Institute. Institutions with major programs focusing on CDR include the Lenfest Center for Sustainable Energy at the Earth Institute, Columbia University, and the Climate Decision Making Center, an international collaboration operated out of Carnegie-Mellon University's Department of Engineering and Public Policy.

The mitigation effectiveness of air capture is limited by societal investment, land use, and availability of geologic reservoirs. These reservoirs are estimated to be sufficient to sequester all anthropogenically generated CO₂.