Carbon capture and storage: More energy or less carbon?

Abstract

Innovations in energy supply have traditionally been valued because they make more energy available than would otherwise be the case and/or make it available at lower cost. Carbon capture and storage (CCS) can also be viewed in this way to some extent, for example, as a means to keep coal as an electricity generation fuel in Europe and the USA. But the underlying driver for CCS is really that less fossil carbon is being emitted to the atmosphere. Since long-term cumulative emissions are the determining factor for climate change, long-term retention of stored CO2 is important. Long-term “leakage” risks also apply, however, to fossil fuels that are displaced in the short term by nonfossil energy sources (i.e., nuclear, renewables) since the fossil fuels may subsequently be used and the CO2 released to the atmosphere. If CCS is to achieve effective reductions in CO2 emissions to the atmosphere, however, it is important that projects are either near carbon-neutral, able to capture around 90% or more of the fossil carbon in the fuel used, or carbon-negative, capturing CO2 from biomass or directly from the air. Another class of CCS project, which involves capturing CO2 from hydrocarbon production (e.g., natural gas purification or oil sands processing) is still carbon-positive since the CO2 from the product fuel is likely to be released to the atmosphere. This class of CCS project should therefore be viewed as a “license to operate” for projects producing fossil fuels but not as an example of the approach that is needed to achieve the large cuts in greenhouse gas emissions (e.g., 80% or more in developed countries by 2050) now being suggested. Near carbon-neutral and carbon-negative CCS projects will have to produce carbon free energy vectors such as electricity, hydrogen, or heat. These in turn can be used to displace direct fossil use by the transport and building sectors. To make CCS available as a reasonably well-proven option by around 2020, a first tranche of demonstration plants need to be deployed as quickly as possible. A second, larger tranche of reference plants then needs to continue the learning process and demonstrate the technology at scale and ready for multiple repeat orders. After this second tranche, CCS should be ready to contribute to a rapid decarbonization of the electricity supply from coal, natural gas, and biomass power plants in developed countries in the decade 2020–2030.