Survey of Energy Resources 2007
Carbon Capture and Storage
Addressing climate concerns means mitigating emissions of greenhouse gases. The power sector is one of the main contributors to worldwide CO2 emissions, and recognises that emissions will have to be addressed in a carbon-constrained future - but without impacting economic growth and energy security. A vital tool in stabilising atmospheric CO2 concentrations is carbon capture and storage (CCS), whereby CO2 is removed from flue gases - from power generation or other industrial activity - and injected underground; for example, into deep saline aquifers or used for enhanced oil recovery.
There are several different types of CO2 capture systems: post-combustion, pre-combustion and oxyfuel combustion. The concentration of CO2, the pressure in the gas flow and the fuel type (solid or gas) are important factors in selecting the appropriate capture system. Pipelines are preferred for transporting large amounts of CO2 for distances up to around 1 000 km. For amounts smaller than a few million tonnes of CO2 per year or for transportation over larger distances overseas, the use of ships, where applicable, to transport CO2 is economically more attractive. Storage of CO2 in deep onshore or offshore geological formations (oil and gas fields, saline formations, unmineable coal beds) uses many of the same technologies that have been developed by the oil and gas industry and has been proved to be economically feasible under specific conditions for oil and gas fields and saline formations, but not yet for storage in unmineable coal beds.
The Intergovernmental Panel on Climate Change (IPCC) has estimated that there is a worldwide storage capacity of at least 2 000 billion tonnes of CO2, which is expected to account for up to 55% of the cumulative mitigation effort up to 2100. Importantly, the IPCC also notes that the costs of mitigation may be reduced by 30% or more when CCS is included in a climate-stabilisation strategy. Studies are under way globally to ascertain more detail regarding the location and capacity of suitable storage sites.
Carbon capture has been undertaken for many years in the oil and gas industry, and in the coal-processing sector: the Dakota Gasification plant in the USA gasifies coal to provide synthetic natural gas and exports the CO2 to Canada, for use in enhanced oil recovery. However, experience is yet to be gained on CCS from a coal-fired power plant. A number of research and development projects worldwide are exploring the issues and opportunities, and demonstration plants are expected to be in operation from 2009 onwards (Fig. 1-5 ).