The energy balance of soybean oil biodiesel production: A review of past studies

Anup Pradhan, Dev S. Shrestha, Jon Van Gerpen, James Duffield

Research output: Contribution to journalArticlepeer-review

87 Citations (Scopus)


Although several studies have found biodiesel to be a renewable source of energy, there has been a claim that it is not. This article investigates models used to calculate the net energy ratio (NER) of biodiesel production to point out the reasons for the contradictory results, compares their strengths and weaknesses, and proposes a uniform model for interpretation of the final result. Four commonly referenced models were compared for their assumptions and results. The analysis revealed that the most significant factors in altering the results were the proportions of energy allocated between biodiesel and its coproducts. The lack of consistency in defining system boundaries has apparently led to very different results. The definitions of NER used among the models were also found to be different. A unified model is proposed for biodiesel energy analysis to answer the renewability question. Using the unified boundary, a range of probable NERs was calculated using bootstrapping. The mean NER on a mass basis was 2.55 with a standard deviation of 0.38. The economic sustainability ratio (ESR) is defined as the monetary value ratio of biodiesel to biodiesel's share of the energy inputs. The average ESR was found to be 4.43 with a standard deviation of 0.6.

Original languageEnglish
Pages (from-to)185-194
Number of pages10
JournalTransactions of the ASABE
Issue number1
Publication statusPublished - Jan 2008
Externally publishedYes


  • Biodiesel
  • Economic analysis
  • Energy balance
  • Life cycle analysis
  • Net energy ratio

ASJC Scopus subject areas

  • Forestry
  • Food Science
  • Biomedical Engineering
  • Agronomy and Crop Science
  • Soil Science


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