Coal-fired boilers in the United States are responsible for approximately one third of theanthropogenic CO_2 emitted. They are however large and stationary sources, and offer perhapsthe best option for attempting to reduce the net emissions. The utility industry is exploringapproaches that can achieve significant reductions at acceptably low overall costs. In broadterms, there are a number of approaches which are described in EPRI’s Electricity TechnologyRoadmap: Powering Progress. These include continuing and accelerating the long-termimprovements in efficiency of production and use of electricity, and the progressivedecarbonization of the fuel. However, if coal is to continue to play a large role in the productionof electricity, some method of removal of some fraction of the CO_2 from the combustion gas, andits storage in a long-term secure repository (‘sequestration’) would seem to be necessary. Thereare a number of factors that will determine how much must be removed and sequestered, and thesecurity required of the sequestration option chosen; the details of these will of course be largelydetermined by the eventual environmental control legislation. The possible associatedenvironmental impacts will also need to be carefully studied. This paper will consider some ofthese issues for a number of the current options, and in particular will review some of theremaining issues related to the ‘biomimetic’ option that EPRI has been looking at.
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