Abstract

A proper First Law energy balance of the soybean biodiesel cycle shows that the overall efficiency of biodiesel production is 0.18, i.e., only 1 in 5 parts of the solar energy sequestered as soya beans, plus the fossil energy inputs, becomes biodiesel. Soybean meal is produced with an overall energetic efficiency of 0.38, but it is not a fossil fuel. If both biodiesel and soybean meal were treated as finished fossil fuels, the overall energy efficiency of their production would be 0.56, ∼ 40% higher than the average overall efficiency, 0.4, of producing ethanol and DDGS from corn patzek 2006z, patzek 2007a. This difference is caused by the high energy efficiency of producing soybean meal, which is 57% of soya beans by mass. Production of corn ethanol alone, with the average overall efficiency of 0.25, is more energy-efficient than production of biodiesel from soybeans with the overall efficiency of 0.18. The results of the current analysis are compared with those by NREL 1998 and Hill et al. 2006.