Process Economics Program Report 263
Biochemical Cellulosic Ethanol
Published: December 2008
World ethanol production is undergoing spectacular growth, which has led to price increases for certain agricultural commodities such as corn. Cellulosic biomass may become an alternative feedstock for ethanol production. 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 cellulosic biomass such as corn stover, corn cobs and municipal solid waste. Four economic models are provided for the following processes: dilute acid pretreatment, concentrated acid hydrolysis, ammonia pretreatment, and conventional corn dry milling. The general conclusions are summarized below:
- It is unlikely that biochemical 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.