BIOLOGICAL FOSSIL CO2 MITIGATION

Over ten times more CO2 is fixed by plants into biomass, and annually released by decomposers and food chains, than is emitted to the atmosp here due to the burning of fossil fuels. Human activity is already dir ectly and indirectly affecting almost half of the terrestrial biologic al C cycle. Management of even a small fraction of the biological C cy cle would make a major contribution to mitigation of this greenhouse g as. Electric power generation is responsible for roughly one third of fossil CO2 emissions. Direct CO2 mitigation processes are those that r educe fossil CO2 emissions from specific power plants. Direct biologic al CO2 mitigation processes include the cultivation of microalgae on f lue-gas or captured CO2, and the cofiring of wood with fossil fuels. I ndirect biological processes, such as growing trees for C storage or f or fueling dedicated biomass power plants, recapture CO2 that already has entered the atmosphere. Indirect and direct CO2 mitigation process es have the same overall effect in reducing global warming potential. Reducing global CO2 emissions from forest destruction and unsustainabl e agricultural and land use practices is one of the most cost-effectiv e, and environmentally beneficial actions that can be taken now to arr est global climate change. Another near-term option is to enhance the substitution of fossil fuels with biofuels. Biofuels are a major sourc e of fuel for the poorer half of mankind. Globally, biofuels could rep lace a substantial fraction of current fossil fuel usage. Cofiring bio mass wastes and residues with coal is one of the lowest-cost, nearest- term options for reducing fossil CO2 emissions at existing power plant s. Long-term demonstrations of biomass cofiring are required at full-s cale coal-fired power plants to document efficiencies, ash characteris tics, biomass preparation and feeding, and other technical issues. Bio mass fuel resources for cofiring can be expanded in the near-term thro ugh greater recovery of wastes and residues in forestry and agricultur e, and in the mid-term through systems that produce biomass specifical ly for use as fuels (energy crops). (C) 1997 Elsevier Science Ltd.