Particulate emissions from biodiesel vs diesel fuelled compression ignition engine

Studies conducted over the last decade have well established a direct relationship between deteriorating human health and diesel engine exhaust. Biodiesel has shown a lot of promise in terms of both its relatively higher combustion efficiency and lower harmful emissions. Biodiesel has the potential to replace a significant amount of the petroleum used to power diesel engines. The emissions from biodiesel are different than petroleum-based diesel and it is important to understand how they are different with respect to the levels emitted and the combustibility of the particulates. One of the major pollutants emitted from engine exhaust is particulate matter (PM). PM emitted from tailpipes contains a variety of toxic contaminants either embedded or adsorbed on its surface. This study provides a one to one comparison between PM emitted from a mid-size engine running on petroleum-based diesel versus biodiesel. The key physical and chemical parameters analyzed include metals, benzene soluble organic fraction, elemental and organic carbon fractions, particle morphology, particle number and size distribution. This is the first study of its kind where various aspects of the PM emitted from a biodiesel-operated engine have been extensively studied. The major results from the study showed that metals that come from engine wear are not present in biodiesel exhaust particulate due to its self lubricating properties. Samples collected of mineral diesel exhaust are relatively darker in color and stickier than biodiesel exhaust. Biodiesel and its blends gave more benzene soluble organic fraction (BSOF) in engine exhaust particulate matter than mineral diesel at all operating conditions. B100 gave higher number of smaller particles in its exhaust than mineral diesel: comprehensively all size particles were also higher in case of B100. Peak particle concentrations for biodiesel were shifted towards smaller size particles. As load increases, B20 emission performance in terms of particle concentrations improves very rapidly and even surpasses mineral diesel emission performance. Scanning electron microscope (SEM) images for B100 and B20 showed granular structure particulates with bigger grain size compared to mineral diesel. Among B100, B20 and mineral diesel, total particle accumulation was maximum for mineral diesel. (C) 2011 Elsevier Ltd. All rights reserved.