Integrated Energy, Environmental and Financial Analysis of Biofuel Production from Switchgrass, Hybrid Poplar, Soybean and Castorbean

Abstract

Biofuels are considered a substitute for petroleum-fuels, but to be viable they should not depend heavily upon non-renewable resources. The objective of this study was to estimate the ultimate amount of energy required to produce liquid-fuels from switchgrass, hybrid poplar, soybean, and castorbean. Emergy (with an "m") accounting was used to integrate all environmental, fossil fuel, and human-service inputs used throughout the production chain from agricultural field to processing facility. Depending on feedstock type and conversion yields, environmental inputs were between 21-44%, fossil fuels were 18-73% and human-derived services were 2-61%. Gallons of transportation fuel produced per gallon of petroleum used ranged from 0.06 to 4.2 for ethanol and 2.6 to 4.4 for biodiesel. No biofuel was made with less than 75% non-renewable resources. Energy embodied in "hidden" indirect paths ranged from 38-99%. The viability of replacing petroleum with cellulosic ethanol or biodiesel is highly questionable.