EVALUATION OF TECHNOLOGY OF GENERATING ELECTRICITY WITH WOODY BIOMASS - ESTIMATE OF REDUCTION IN CO{sub}2 EMISSION

摘要

We evaluated processes for converting woody biomass-to-energy and estimated the gross reduction in CO{sub}2 emissions (R{sub}G) made possible by the use of these processes compared with coal or diesel fuel burning. We assessed 4 processes: combustion for steam turbine power generation, gasification for gas turbine power generation, pyrolysis for diesel engine-driven power generation, and ethanol fermentation for diesel-enginedriven power generation. R{sub}G values were 385 kg-C/t-biomass, 499 kg-C/t-biomass, 345 kg-C/t-biomass, and 198 kg-C/t-biomass, respectively. We also estimated the net reduction in CO{sub}2 emissions (R{sub}N), by considering 5 CO{sub}2 release processes: (a) biomass production, from field preparation to harvest, (b) collection of biomass, (c) biomass transportation to power generating plant, (d)pretreatment of biomass for power generation, and (e) conversion of biomass to fuel (only in the cases of pyrolysis and fermentation). Two transport scenarios were considered: the use of biomass generated in Japan and the use of biomass imported from abroad. The process that reduced CO{sub}2 emission most effectively in both scenarios was gasification for power generation.