Emissions from nine heavy trucks fueled by diesel and biodiesel blend without engine modification

Biodiesel, a fuel that can be made from renewable biological sources such as vegetable oils or animal fats, has been recognized recently as an environment friendly alternative fuel for diesel engines. In this paper, we describe a study that compared exhaust emissions from in-use heavy trucks fueled with a biodiesel blend with those from trucks fueled with petroleum diesel. The biodiesel blend tested is a mixture of 35% biodiesel and 65% petroleum diesel, a blend designated as B35. The study is based on the field test results from West Virginia University's Transportable Heavy Duty Chassis Dynamometer Emissions Testing Laboratory and sponsored by the U.S. Department of Energy. The heavy trucks we tested performed well when the originally equipped compression-ignition engine (diesel engine) was fueled with B35 without any engine modifications. Fuel economy (in terms of gallon per mile) of the two fuels was about the same. The emissions test results have shown that the heavy trucks fueled by B35 emitted significantly lower particulate matter (PM) and moderately lower carbon monoxide (CO) and hydrocarbon (HC) than the same trucks fueled by no. 2 diesel (D2). Oxides of nitrogen (NOx) emissions from B35 and D2, however, were generally in the same level. Emissions variations from two different engine models and two driving cycles were also observed. Although we recommend more tests for biodiesel vehicles, the data obtained in this study indicate that biodiesel has promise as an emissions-reducing alternative fuel for diesel engines.