Contributions of biomass burning to global and regional SO2 emissions

Harmful SO2 largely originates from coal and oil combustions, but in some areas the biomass burning contribution could not be ignored. Here, we evaluated SO2 emissions from biomass burning (BB-SO2) with largely focusing on regional difference and temporal trends in the relative contributions of biomass burning from different sectors. Globally, the biomass burning emitted 4.26 (3.20-6.20) T-g SO2 in 2014, contributing 4.0% of the total SO2 emissions stemming from anthropogenic sources and natural open fires. But in some African and South Asian countries, biomass burning was a major source of SO2 with the contribution as high as 80-90%. Regarding sector contributions of biomass SO2, open fires contributed nearly half, followed by the residential sector (similar to 29%) on the global scale, however, substantially different profiles were revealed across countries. Residential sector is the largest anthropogenic BB-SO2 source in the developing countries, while in the developed countries, industry and energy production were the two main anthropogenic BB-SO2 sources. From 1960 to 2014, biomass SO2 emission, either the absolute amount or the relative contribution to the total, increased in the U.S. and Europe, and the contributions were over 20% in some countries. The biomass burning SO2 emission showed an increasing trend in India and a unimodal change in China, while a decreasing trend in the relative contributions were revealed in these two largest developing countries, which were 2.7% and 0.8%, respectively in 2014. With unignorable biomass burning contribution to SO2, as well as other hazardous air pollutants, in some regions, it is suggested that in assessing climate and health impacts of promoted biomass utilization when phasing out of fossil fuels, multiple components should be co-evaluated.