Experimental study on characteristics of emissions and fuel consumption for combines

Agricultural machinery has been considered an important contributor to atmospheric pollution. However, as the volume of agricultural machinery increases, studies on the emission characteristics and fuel consumption of agricultural machinery have been rarely reported, especially for real-word characteristics of combines' emissions and fuel consumption. Only twelve large and middle-sized agricultural tractors were tested by using a portable emission measurement system in 2013, and the emissions characteristics of tractors were studied. Therefore, it is difficult for the policymakers and researchers to understand the actual emissions characteristics and fuel consumption of combines. In order to deepen the understanding of the factual emission and fuel consumption of agricultural machinery, 10 combines were tested by using a portable emission measurement system in this study, These combines' emission standards included Pre-China I (the combines before 2007 model year were defined as Pre-China I), and China I and China II. All the tested combines' fuel was 0# diesel oil bought on the market. Three typical operating modes were included in the tests, namely idling, moving, and working. Both emission factors and fuel consumption were obtained in different operating modes. The results showed that fuel consumption of grain combines was 6.799 L/h, as for corn combines, the value turned out to be 10.287 L/h. The largest averaged fuel consumption from grain combines was under working among the three modes, as same as the corn combines. It was also indicated that instantaneous fuel consumption during working mode was higher than that during idle and moving modes. However, fuel-based CO and HC emissions measured at idling appeared higher than that measured in moving and working modes. Fuel-based NO_x and PM emissions revealed their peaks in moving and working respectively. Generally, the emission factors of grain combines were higher than that of corn combines. The 400 combines' annual working hours were obtained in Shaanxi province, and the result showed the annual working hours of combines was 140~160 h. In this study, the averaged annual working hours of combines was considered as 150 h. Based on annual working hours, the populations, and the fuel consumption, the fuel consumptions of total grain combines was 74.59×10⁴ tons, and that of corn combines was 16.97×10⁴ tons in 2010. As estimated, the total emission of CO, HC, NO_x, and PM from combines in 2010 were 2.54×10⁴t, 0.97×10⁴t, 4.84×10⁴t, and 0.47×10⁴t, and NO_x and PM emissions generated from combine operations accounted for 1.91% and 1.94% of the total vehicle emission in China in 2010. In addition, approximately 84.5%~84.7% of combine emissions in China were produced in the top 10 provinces of combine application in 2010, and the total emissions of CO, HC, NO_x, and PM from each province of the top 10 were also presented in this paper. It was the first time for this study to test emissions and fuel consumption of combines, and the data could help policymakers and researchers to understand the real-world characteristics of combines' emissions and fuel consumption.