A comparison of measured diesel emissions in agriculture and Australian National Standard Emission Factors

A comparison of measured diesel emissions in agriculture and Australian National Standard Emission Factors

Diesel engines used in highly mechanised agriculture can contribute a significant proportion of the total green house gas emissions generated on farm. Stringent GHG emission control legislations internationally imposed for off-road diesel engines are applied on tractors as part of o�-road mobile sources. Australian national GHG emission factors (EF) are based on the Intergovernmental Panel
on Climate Change Guidelines emissions factors, and in turn, those emissions factors are taken from studies conducted in 1975. The accuracy of these EFs are questioned by many researchers due to, i) no consideration of the transient effects of engine performance on emissions, ii) measurements were based on a relatively small sample of tractors and iii) studies were based on older tractor
models with engine technology superseded by developments during the last 40 years. Inaccurate emissions factors lead to inaccurate estimates of the emission thereby over reporting in the annual emission inventory report. This research work addresses the issue related to transient effects and engine technology that affect the emission factors. A 68.8 kW, Belarus 920 tractor was used in this study to evaluate the tractor performance and the exhaust gas emission component such as CO, CO2 and NOx. This study aims to evaluate Australian emission factors for agricultural tractor considering the transient effects on tractor operating condition. Steady-state test (ECE R-49) and the European Stationary Cycle Test were used to assess the emission factors. The experimental apparatus consists of PTO dynamometer, fast response portable gas analyser type CODA, speed sensors, flow rate measuring systems, thermocouples and pressure transducers.
Transient test result was compared with steady-state test result. The experimental results demonstrated that transient produce higher emission for CO2 and NOx (3.73% and 33.58% respectively). CO emission of transient test was lower by 44.26% than steady-state emission.
CO2-equivalent emissions were calculated for the ECE R-49 , ESC, and Constant Speed tests based on time integrated fuel consumption using the Australian emission factors. The calculations resulted in 11.8% (on average) less emissions than real measurements indicating there is a need for revising the emission factors or the followed methodology.