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LIFE CYCLE ASSESSMENT OF ELECTRICITY GENERATION ALTERNATIVES
Citation:
SMITH, R. L. LIFE CYCLE ASSESSMENT OF ELECTRICITY GENERATION ALTERNATIVES. Presented at Camelia Workshop on Electricity Production, Paris, FRANCE, January 20 - 21, 2005.
Impact/Purpose:
To inform the public.
Description:
This presentation summarizes various electricity and electricity/steam cogeneration alternatives. Among these alternatives, are fossil fuel and biomass power generation plants. These plants have different designs due to the need in fossil fuel (coal) plants to include process units for selective catalytic reduction, fly ash collection, and flue gas desulfurization. Common analyses techniques of power plants include energy flow diagrams, which for instance show where 100 Btu's of fuel energy end up (e.g., electricity, steam, wasted heat, stack losses, internal plant use). A preferred analysis is to use life cycle assessment. In studying the emissions from power plants, common pollutants include NOx, SO2, and CO2. In particular, the CO2 emitted is of interest as a greenhouse gas. (A short description of the greenhouse effect and a global carbon cycle are presented.) Finally, a review of life cycle analyses is presented on coal-fired, natural gas combined cycle, biomass crop, and biomass residue fuels for electricity generation. The overall global warming potentials for these processes show that (unlike the other systems) residue biomass receives a credit for avoiding biomass decay into CO2 and methane gases. This credit gives residue biomass a negative net CO2 equivalent life cycle emission profile, although this credit only applies if the residue biomass would have been left to decay otherwise. While the quantity of biomass residue available may be limited, it is possible for a combination of various power generation processes to achieve a zero or net negative CO2 equivalent emission rate. In any case, the amounts of life cycle CO2 equivalents from various types of power plants can be summed, and the total used as an objective for minimization within feasibility (e.g., economic) constraints.