Establishment And Characteristic Analysis Of Solid Fuel Combustion Emission Inventory In Rural Areas Of Western China

As a large amount of Solid fuels such as biomass,coal in rural areas are consumed in rural areas in China,the gaseous pollutants and particulate matter emitted by their burning have adverse effects on the environment and human health,and have become one of the important sources of air pollution that cannot be ignored.In this study,field sampling was conducted in 9western provinces（Gansu,Guizhou,Ningxia,Qinghai,Sichuan,Shaanxi,Xinjiang,Yunnan,Tibet）using the self-assembled portable dilution sampling system.The CO₂,CO,NOx,SO₂,OC,EC and PM_2.5 emission factors of straw,fuelwood,and coal combustion in each province were obtained.Based on the collected activity level data,the provincial emission inventories for gaseous pollutants and particulate matter from solid fuel burning in the western region in 2018 were established.The results show that due to the difference of burning habits（including fuel type and stove type）among provinces,there are certain differences in the emission factors among provinces.Specifically,the emission factors of CO₂,CO,NOx,SO₂,OC,EC,PM_2.5 are in range of1334-2741g/kg,62.55-261.91g/kg,0.15-1.95g/kg,0.02-4.51g/kg,0.92-12.01g/kg,0.28-2.74 g/kg,3.63-21.88g/kg,respectively.Overall,the type of stove has a relatively great impact on the NOx and SO₂ emission factors of straw burning,and has a greater impact on the NOx emission factor of firewood burning,which is related to the burning efficiency and burning temperature of different types of stoves,as well as the material composition of fuel types.Therefore,the combination of stove and fuel can have a more complex impact on emission factors.Based on the provincial emission factors,the provincial emission inventories were obtained.The results show that the total emission of CO₂,CO,NOx,SO₂,OC,EC and PM_2.5from solid fuel burning in nine provinces in western rural areas of China was 189.4 million tons,10.6 million tons,85600 tons,125900 tons,483100 tons,131200 tons,893000 tons in 2018,respectively.Among them,coal burning emissions accounted for the largest proportion,followed by firewood,and straw was the smallest.The total emission of pollutants was 131.51 million tons,51.39 million tons and 18.78million tons,respectively.In addition,there are obvious regional differences in emissions,with high CO₂,CO emissions concentrated in areas with high coal consumption,such as Xinjiang,Shaanxi and Guizhou.The areas with high NOx emissions were Guizhou and Xinjiang,which were mainly contributed by coal burning.Guizhou,Shaanxi,and Xinjiang had high SO₂ emissions,of which coal emissions were the main contributors in Shaanxi and Xinjiang,while firewood emission was the main contributor in Guizhou.High PM_2.5,OC,EC emissions were concentrated in areas with high biomass burning,such as Yunnan,Guizhou and Sichuan.The emissions of CO₂,CO,NOx,SO₂,OC,EC and PM_2.5 in the 9 provinces during the heating period accounted for between 58%and 65%of total emissions.The areas with more than 70%of the pollutant emissions during the heating period were concentrated in areas with large heating demand in Xinjiang and Tibet,and areas with high biomass fuel consumption in Sichuan and Guizhou.The average emissions estimated by each province using the same emission factor are compared with the provincial emissions estimated by each province using the provincial emission factor.The result shows that there was overestimation or underestimation of the emissions compared with the actual emissions.Using the provincial emission factors can reduce the uncertainty of emissions inventory.According to the emission characteristics of the western region,it is recommended to reduce the use of unprocessed biomass fuels.The biomass such as straw and fuelwood can be processed into small physical forms,or carbonized,and high-performance biomass stoves can be used to effectively reduce the pollution emissions caused by biomass burning.In areas with high coal consumption such as Xinjiang,it is suggested to further improve the quality of coal,and use as much coals such as anthracite that are easy to burn completely as possible.For areas where kang and brick stoves are used,such outdated stoves should be improved to improve combustion efficiency and heat transfer efficiency.Due to the large proportion of emissions by heating in winter,it’s necessary to reduce the use of scattered coal,accelerate the process of rural clean heating renovation,increase financial subsidies,and implement measures such as coal-to-electricity and coal-to-gas conversion.