A new energy lifecycle study for soybean biodiesel has updated the first comprehensive 1998 life cycle study for soybean biodiesel produced n the United States. The study is contained in a report by scientists from the University of Idaho and the United States Department of Agriculture (USDA). A life cycle study of a particular biofuel product is essentially an accounting of material and energy flows, as it goes through the process of feedstock plantation/transportation, biofuel processing, and final use as fuel. It allows an assessment, whether the biofuel product has a positive or negative net energy yield or whether it has positive or negative emissions of an environmentally-polluting material (such as greenhouse gases). The "fossil energy ratio" is one index for assessing energy yield. The 1998 study pegged the fossil energy ratio of soybean biodiesel at 3.2. That is, 3.2 units of energy are produced for every unit of fossil fuel used for its production. In contrast, petroleum diesel has a fossil energy ratio of only 0.84. The recent life cycle study shows a higher (i.e. much better) fossil energy ratio for soybean biodiesel at 4.56. The much improved value (based on 2002 soybean production data) is attributed to the following factors: (1) better (more energy efficient) soybean crushing facilities, (2) improved (agricultural) soybean yields, (3) less fertilizer/pesticide use. The full report can be accessed at the USDA website (URL above)..