Greenhouse-Gas Emissions from Biofuel Use in Asia

Abstract

Biomass is a primary fuel for much of the world's population. In somedeveloping countries it can contribute 80-90% of total primary energyconsumption. In Asia as a whole we estimate that biomass contributesabout 22 EJ, almost 24% of total energy use. Much of this biomass iscombusted in inefficient domestic stoves and cookers, enhancing theformation of products of incomplete combustion (PIC), many of which aregreenhouse gases. An inventory of the combustion of biofuels (fuelwood,crop residues, and dried animal waste) in Asia is used to developestimates of the emissions of carbon-containing greenhouse gases (CO2,CO, CH4, and NMHC) in Asian countries. The data are examined from twoperspectives: total carbon released and total global warming potential(GWP) of the gases. We estimate that biofuels contributed 573 Tg-C in1990, about 28% of the total carbon emissions from energy use in Asia.China (259 Tg-C) and India (187 Tg-C) were the largest emittingcountries by far. The majority of the emissions, 504 Tg-C, are in theform of CO2; however, emissions of non-CO2 greenhouse gases aresignificant: 57 Tg-C as CO, 6.4 Tg-C as CH4, and 5.9 Tg-C as NMHC.Because of the high rate of incomplete combustion in typical biofuelstoves and the high GWP coefficients of the products of incompletecombustion, PIC comprise an even larger share of biofuel emissions whenmeasured in terms of global warming potential (in CO2 equivalents): 48%over a 20-year time frame and 26% over 100 years. Even when the biofuelis assumed to be harvested on a completely sustainable basis (all CO2emissions are reabsorbed in the following growing season), PIC emissionsfrom biofuel combustion account for almost 5% of total carbon emissions(including emissions from fossil-fuel combustion) and nearly 25% of CO2equivalents in terms of shortterm (20-year) GWP.