Environmental impact assessment of the mechanical shaft work produced in a diesel engine running on diesel/biodiesel blends containing glycerol-derived triacetin

Abstract

Global application of biodiesel in the transport sector has rapidly expanded over the last decade, however, efforts to overcome its main shortcoming, i.e., increase in NOx emissions compared with diesel, are still underway. In light of that, parameters/strategies capable of mitigating biodiesel NOx emissions are of wide interest to further enhance the sustainability aspects of this green fuel. Among various options put to test, the use of fuel additives due to its simplicity and cost-effectiveness has attracted a great deal of attention. In this study, the mechanical shaft work produced by a diesel engine fueled with various diesel/biodiesel blends (B5 and B20) containing glycerol-derived triacetin was scrutinized from environmental viewpoint. Neat petro-diesel, B5, and B20 were also considered as control fuels. Two environmental evaluation methodologies, namely discrete emissions analysis and consolidated life cycle assessment (LCA) were considered to assess the impacts of fuel composition, engine speed, and engine load on the environmental burdens of the shaft work produced. According to the results obtained, the outcomes of both methods considered herein were profoundly affected by engine load and speed. Even though triacetin inclusion into both B5 and B20 profoundly affected the outcomes of emissions analysis, its application did not lead to any spectacular differences in the results of LCA method compared with petro-diesel. More specifically, triacetin incorporation into fuel blends neutralized the unfavorable impacts of biodiesel addition in terms of NOx emissions. However, incorporating triacetin into diesel/biodiesel blends in general did not profoundly mitigate the environmental impacts of the shaft work produced in terms of LCA damage categories as well as the total environmental impacts. Overall, using triacetin as combustion improving agent did appear to be an efficient strategy from the LCA viewpoint considering the current production technologies. In addition, LCA approach was found to be more a comprehensive decision-making approach compared with discrete emissions analysis for evaluating the environmental impacts of the shaft work produced by internal combustion engines.