This model was developed for use with spreadsheet software (Excel) in the Agricultural & Biosystems Engineering Department and Agribusiness & Applied Economics Department of North Dakota State University over the period 2003-05. The model was developed by Mr. Dhruv Tapasvi as part of his M.S. Thesis, under the supervision of Dr. Dennis Wiesenborn and Dr. Cole Gustafson.
Some explanation and detail is provided by the paper:
Tapasvi, D., D. Wiesenborn, and C. Gustafson. 2005. Process modeling approach for evaluating the economic feasibility of biodiesel production, Transactions of the ASABE, 48:2215-2221. 
DISCLAIMER: The model is based upon published literature and common process engineering assumptions. Every effort has been made to accurately model the biodiesel process. However, this model is intended only as a demonstration of the biodiesel process modeling concept, and has not been fully and systematically tested or checked for errors. Neither the authors nor NDSU will be liable for any damages or loss of profits that may result from use of this biodiesel process model.