ENERGY ANALYSIS OF RAPE METHYL-ESTER (RME) PRODUCTION FROM WINTER OILSEED RAPE

Energy ratios were calculated for production of the rapeseed-oil-based diesel substitute rape methyl ester (RME) from winter oilseed rape. T he energy ratio of a biofuel can be defined as the ratio of the non-re newable energy used in its production to the energy value of the fuel and any utilised by-products, i.e, energy input:energy output. For eac h energy input and output, a range of energy values was calculated to account for different soil and weather conditions and variation in yie ld. In addition, the range of energy inputs calculated accounted for v ariation in published estimates of the amount of energy required for v arious processes. The range of inputs and outputs included values calc ulated for worst-case (i.e, lowest seed yield, highest pesticide appli cations, etc.) and best-case scenarios, and two intermediate values, w hich represented inputs and outputs expected under typical conditions in Scotland. From this data, energy ratios were calculated for rape me thyl ester production under best-case, worst-case and intermediate sce narios, with and without the inclusion of by-products. The results ind icated that RME production is sustainable under all but the worst cond itions. Utilisation of rapemeal greatly improved the energy ratio, but there remained a net loss in energy under the worst-case scenario. Gl ycerol utilisation had relatively little effect on the energy ratio, w hile the use of straw resulted in a net energy gain from the productio n of RME under all scenarios.