Estimation of emissions from field burning of crop straw in China

Emissions resulting from crop straw field burning in China, which have caused serious environmental problems in China, are estimated in this paper. From the county-level data of crop production in 2000-2003 from the government statistics, taking into account the ratio of residue and grain, the total amount of crop straw production is estimated to be about 600 Tg per year, 76% of which are rice, wheat and corn straw. With reference to the data of living standards, the percentage of crop straw burnt in fields for counties are obtained and consequently the total amount of burnt straws is approximately 140 Tg/year. With the emission factors from literature and experiments, appropriate emission factors have been obtained. The total amounts of PM, SO2, NO (x) , NH3, CH4, BC, OC, VOC, CO, CO2 emissions from field burning of crop straw in China are estimated. All emissions are presented at county level. Some pollutants, such as BC, VOC, OC, CO and CO2, are contributing a major portion to the total emissions of China. This paper uses a map with resolution of 0.2 degrees x 0.2 degrees to present the PM emissions distribution from crop straw burnt in 2003. The results show a significant regional unevenness of emissions, with larger amounts of pollutions coming from the provinces in eastern and northeast China. The regions with higher emissions per unit area are located as a belt stretching from northeast China to eastern China.