Process Economics Program Report 270
Thermochemical Cellulosic Ethanol
Published: December 2009
World ethanol production has experienced spectacular growth. This growth has been based on starch and sugar feedstocks. Cellulosic biomass has the potential to become an alternative feedstock for ethanol production. Cellulosic biomass consists of forestry wastes, agricultural residues and municipal sold waste (MSW).There are numerous challenges, both technical and infrastructure related, associated with commercializing lignocellulosic biomass as feedstock for ethanol production. While large quantities of various crop wastes go unused throughout the world, these lignocellulosic materials are difficult to efficiently convert into chemical products due to their complex polymeric structures. Innovative new technologies that couple biotechnology and chemistry with process engineering are necessary in order to achieve efficient commercial processes. To support commercialization, the Department of Energy announced in 2007 that the government would invest up to $385 million in six commercial scale U.S. projects for lignocellulosic ethanol. Four of the six projects will utilize biochemical conversion technologies and the others will utilize thermochemical conversion technologies.
In this report, PEP presents process designs and associated cost estimates for producing ethanol in the United States from syngas derived from cellulosic biomass. We examine the conversion of wood chips to syngas followed by its conversion to ethanol via chemical catalysis and also via fermentation. We also compare this economics to the production of ethanol via dry corn milling. This report supplements PEP Report 263 Biochemical Cellulosic Ethanol (2008).The general conclusions are summarized below:
- It is unlikely that thermochemical cellulosic ethanol will be competitive with corn dry milling in the near future. This is largely due to the high capital investment required for a new plant. However, recent legislation in the United States provides various incentives for commercialization of cellulosic ethanol.
- Large scale initiatives underway in the United States could change the competitive situation of cellulosic ethanol in the longer term. Some of these initiatives include development of feedstock infrastructure to lower the potential cost of cellulosic feedstock. Other initiatives are underway related to processing technologies for lowering fixed capital requirements.