Multi-type quantitative study on emission factors of agricultural tractors blended with bio-diesel in mountainous areas of plateau environment

Analysis of agricultural tractors burning soybean oil B10 (10% soybean oil biodiesel + 90% diesel), B30 (30% soybean oil biodiesel + 70% diesel), and waste cooking oil W10 (10% waste cooking oil + 90% diesel) when driving on mountainous roads in a plateau environment and diesel pollutant emissions. The results show that the effective fuel consumption rate (BSFC) decreases as the engine speed increases, while the increase in the proportion of biodiesel oil will lead to an increase in BSFC. In addition, the emission factors of CO, NO_x, CO₂ and HC emitted by agricultural tractors were characterized through four aspects: engine power, fuel consumption, driving speed and driving time. In terms of CO emissions, compared with soybean oil B10, the proportion of biodiesel oil in soybean oil B30 increased, and the emission factor based on engine power decreased by 6.18%. Compared with diesel, the emission factors of soybean oil B10, B30 and waste cooking oil W10 based on engine power are reduced by 23.66%, 24.13% and 26.85% respectively. In terms of NO_x emissions, when soybean oil B10 and waste cooking oil W10 are blended, the emission factor of waste cooking oil W10 based on engine power is 6.24% higher than soybean oil B10; in terms of CO₂ emissions, the emission factor based on fuel consumption shows that soybean oil B10, B30 and waste cooking oil W10 are all higher than diesel, which shows that blending biodiesel can promote more complete combustion, thereby increasing CO₂ emissions. In terms of HC emissions, the HC emission factor values of biodiesel based on engine power are higher than those of diesel, and the HC emission factor based on engine power is 1.52 times the recommended value in the "Technical Guidelines for the Preparation of Non-Road Mobile Source Air Pollutant Emission Inventories". As the proportion of biodiesel oil increases, the HC emission factor based on fuel consumption also increases accordingly.