Monday, May 5, 2008 - 8:30 AM
4-02

A Comparison of Rigorous Process and Economic Data for Biochemical and Thermochemical Ethanol Production Technologies

Andy Aden and Thomas Foust. National Bioenergy Center, National Renewable Energy Laboratory, 1617 Cole Blvd, Golden, CO 80401

By signing into law the Energy Independence and Security Act of 2007, a renewable fuels standard (RFS) was established for using 36 billion gallons of ethanol, of which over half will be derived from lignocellulosic feedstocks by 2022.  Questions remain as to which technologies will enable this change.  Multiple technologies exist for converting lignocellulosic biomass into a multitude of biofuels such as ethanol.  Biochemical approaches include dilute acid, concentrated acid, and enzymatic hydrolysis.  Thermochemical approaches include a number of gasifier technologies with multiple fuel synthesis options as well as pyrolysis conversion options.  Previous attempts to examine the pros and cons and comparative economics of biochemical and thermochemical biofuels production have been at high levels with inconsistent metrics of comparison. Hence the need for very rigorous and detailed comparisons of biochemical and thermochemical routes to truly ascertain the real advantages and disadvantages of each.

 

In this paper, the advantages and disadvantages of biochemical and thermochemical biofuels production will be explained.  In addition, detailed capital and operating costs are compared for two rigorous designs: a thermochemical approach using gasification and mixed alcohols synthesis, and a biochemical approach using enzymes and mixed sugar fermentation.  Comparative analysis of these two rigorous studies has shown that either present viable technological options for cellulosic ethanol production that have unique advantages depending on the locally available feedstock base and other localized factors.  There is no clear winner in terms of yield, capital cost, operating costs, etc.  Finally, synergies between the two technical routes will be examined.


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