Biological Systems Engineering


Date of this Version



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The BESS model is a software tool to calculate the energy efficiency, greenhouse gas (GHG) emissions, and natural resource requirements of corn–to-ethanol biofuel production systems. The model provides a “cradle-to-grave” analysis of the production life cycle of biofuels from the creation of material inputs to finished products, producing an inventory of distributed GHG emissions from fossil fuels and a few key indirect emissions in the production life cycle. The model parameters can be set by the user to achieve the highest accuracy in evaluating a single corn-ethanol biorefinery and its surrounding feedstock crop production zone. The model equations and summary reports are unalterable, providing the characteristics needed to serve as certification software to evaluate the environmental impact of biofuels for industry advancement. We anticipate users of the BESS model will include policy makers, regulatory agencies, researchers, secondary and university teachers, media groups, non-governmental organizations, and industry professionals concerned with optimizing economic and environmental performance of biofuel production systems. Specific uses include:

(a) As a certification tool for evaluation of the environmental impact of local biofuel production systems. Systems can be compared against standard reference scenarios, identifying all parameters changed and differences in output results.

(b) Estimating net energy yield, efficiency, petroleum requirements, and net carbon and GHG emissions of an individual biofuel production system (e.g. a single biorefinery) in a specified agricultural production domain that provides the majority of the feedstock; estimation of the required feedstock production area, fertilizer and pesticide inputs, and water requirements (for irrigation and the ethanol plant) based on user input of the crop production parameters or default parameters based on current average values and typical biorefinery design.

(c) Sensitivity analyses of model parameters on biofuel system performance and environmental impact using different combinations of cropping systems, production technologies, and co-product utilization schemes.

(d) Conducting ex ante analyses of the impact of policies and new technologies on biofuel system performance and environmental impact (e.g. life cycle energy efficiencies and GHG emissions of the closed-loop system vs. traditional technologies; coal vs. natural gas as the energy source for a biorefinery, etc.)

(e) Regional, state, or national analyses of biofuel production systems.

(f) Land-use planning for site selection of new biorefineries given crop yield levels, water quantity concerns, and demand from other production facilities and livestock operations within a specified area for co-product use.

(g) Estimation of GHG-emissions intensity of fuel for regulators (e.g. California Low Carbon Fuel Standard, Energy Independence and Security Act of 2007), or for calculating GHG emissions trading credits for ethanol biorefineries.

(h) Educational and research tool for exploring corn-ethanol as an energy system and its associated natural resource requirements.