Life cycle analysis of soybean biodiesel production /by Anup Pradhan.

Biodiesel is a bio-based fuel that has become a popular substitute for diesel fuel. Despite its rapid growth and several studies showing that biodiesel is a renewable energy source, others claim that the use of biodiesel does not reduce petroleum use. Past biodiesel life cycle analyses (LCA) making those claims differed in system boundaries, data sources, and co-product allocations resulting in a wide range of energy and carbon balance results.;This research critically reviews, proposes a unified model, and updates the biodiesel LCA. The LCA of biodiesel production using data from 2002 U.S. soybean agriculture resulted in the fossil energy ratio (FER) of 4.56. This is a 42% improvement over the study conducted by National Renewable Energy Laboratory (NREL), which used 1990 U.S. soybean agriculture data. The total carbon dioxide (CO 2) emission was reduced by 84.44% compared to petroleum diesel, which is a 28% improvement over the NREL study. The greenhouse gas (GHG) emission was reduced by 83.80% compared to petroleum diesel, which complies with the 50% GHG reduction threshold for the biomass-based diesel as required by the Renewable Fuel Standard (RFS2) of U.S. Environmental Protection Agency (EPA).;The LCA results are likely to improve over time with the increasing improvements in soybean production and processing sectors. For every one bushel increase in soybean yield, FER increases by about 0.45%. The FER is estimated to reach 4.69 in the year 2015 when soybean yield is projected to increase to 45.3 bushels per acre. However, the LCA should be practiced on individual biodiesel plants because the LCA estimates based on a national average do not necessarily represent individual plants.;Effective tools are yet to be developed for estimating land use impacts on biofuel expansion. In the United States, soybean is mainly produced from existing agricultural land, hence there is not necessarily a land use change. Also, biodiesel expansion is not an automatic cause of deforestation. Since 2004 to 2009, Amazon deforestation in Brazil has decreased by 75%, while the production of biodiesel in U.S. and the world really took off during this period.Thesis (Ph. D., Biological and Agricultural Engineering)--University of Idaho, May 2010