Energy- and exergy analysis of rape seed oil methyl ester (RME) production under Swedish conditions

In this study the rape seed oil methyl ester (RME) production chain was analysed with respect to its energy- and exergy efficiencies. The differences between results from an ordinary energy analysis and an exergy analysis of the production were also quantified and discussed. The sensitivity of the results to changes in some of the most important input parameters were then analysed in order to find production strategies that increase the exergy efficiency. The study was applied to rape seed cultivation situated in southern Sweden. The rape seed oil was hot pressed in a large-scale plant, and the RME was esterfied in the same factory as that in which in the rape seed oil was pressed. Both direct and indirect energy and exergy flows used for RME production were included. The analysis showed that a large part of the energy and exergy used to produce RME was related to nitrogen fertilizers and diesel fuels. Another important conclusion was that the exergy efficiency of the production in general is higher than the energy efficiency. A third conclusion was that it is possible, by using alternative production strategies, to improve the exergy efficiency without decreasing the energy efficiency.