Greenhouse-gas emissions from biofuel combustion in Asia

An inventory of biofuel combustion is used to develop estimates of the emissions of carbon-containing greenhouse gases (CO2, CO, CH4, and NMHC) in Asian countries. It is estimated that biofuels contributed 573 Tg-C (teragrams of carbon; 1 Tg=1012 g) in 1990, about 28% of the total carbon emissions from energy use in Asia. China (259 Tg-C) and India (187 Tg-C) were the largest emitting countries. The majority of the emissions, 504 Tg-C, were in the form of CO2; however, emissions of non-CO2 greenhouse gases were significant: 57 Tg-C as CO, 6.4 Tg-C as CH4, and 5.9 Tg-C as NMHC. Because of the high rates of incomplete combustion in typical biofuel stoves and cookers and the high global warming potentials (GWP) of the products of incomplete combustion (PICs), biofuels comprise an even larger share of energy-related emissions when measured in terms of total GWP (in CO2 equivalents): 38% over a 20-year time horizon and 31% over a 100-year time horizon. Even when the biofuel is assumed to be harvested on a completely sustainable basis (all CO2 emissions reabsorbed in the following growing season), PIC emissions from biofuel combustion account for 4.5% of the total carbon emissions and 23% of CO2 equivalents on a short-term (20-year) GWP basis.