Biogas is used in gas engine cogeneration to obtain electricity and heat. However, only the biogas produced is stored in the plant. Hence, we developed dual-fuel biogas tractors that can be operated with biogas and diesel. Their basic performance in the steady state was tested. The results of power take-off shaft (PTO) performance tests showed that tractor operation was stable at all engine speeds and under loads. The maximum engine torque and power in the dual-fuel model were higher than the conventional values by 10%. The maximum fuel replacement rate was 86%. NOX and CO2 emissions decreased by 8% and 11%, respectively, in the dual-fuel mode. However, CO and HC emissions increased because excess biogas prevented diesel fuel combustion.
Biogas tractors were developed for agricultural purposes with the aim of partially replacing diesel with biogas. This paper mainly discusses the performance and reduction of fuel consumption of these tractors.
The results showed that dual-fuel operation reduced diesel consumption in all field tests, while realizing the same working efficiency. The maximum decrease in fuel consumption was 73% in hay rake operation. The maximum decrease in fuel replacement rate was 79% in broadcaster operation. Furthermore, by using a dynamometer to determine the actual engine power and load in field tests, we reproduced the engine speed and estimated the engine load. Finally, the fuel consumption performance of the tractors at actual engine speed and power was determined.