A limited LCA comparing large- and small-scale production of rape methyl ester (RME) under Swedish conditions

Abstract

Abstract Production of rape methyl ester (RME) can be carried out with different systems solutions, in which the choice of system is usually related to the scale of the production. The purpose of this study was to analyse whether the use of a small-scale RME production system reduced the environmental load in comparison to a medium- and a large-scale system. To fulfil this purpose, a limited LCA, including air-emissions and energy requirements, was carried out for the three plant sizes. For small plants and physical allocation, the global warming potential was 40.3 g CO2-eq/MJfuel, the acidification potential 236 mg SO2-eq/MJfuel, the eutrophication potential 39.1 mg PO43−-eq/MJfuel, the photochemical oxidant creation potential 3.29 mg C2H4-eq/MJfuel and the energy requirement 295 kJ/MJ fuel . It was shown that the differences in environmental impact and energy requirement between small-, medium- and large-scale systems were small or even negligible. The higher oil extraction efficiency and the more efficient use of machinery and buildings in the large-scale system were, to a certain degree, outweighed by the longer transport distances. The dominating production step was the cultivation, in which production of fertilisers, soil emissions and tractive power made major contributions to the environmental load. The results were, however, largely dependent on the method used for allocation of the environmental burden between the RME and the by-products meal and glycerine. This indicates that when different biofuels or production strategies are to be compared, it is important that the results are calculated with the same allocation strategies and system limitations.