Cellulosic Biorefineries: An Ethanol Revolution

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The Energy Independence & Security Act of 2007 contained a number of mandates with respect to renewable fuels. One of these mandates called for the production of 16 billion gallons of cellulosic or biomass-based fuel by the year 2022. This simply means producing ethanol from nonstarch sources such as corn stover and cobs, wheat straw, switchgrass, wood, sugarcane bagasse, agricultural residues, municipal solid waste, garden and lawn clippings, and rice hulls. In 2009, a total of 10.75 billion gallons of corn (starch) ethanol were produced from 170 production facilities operating in 21 states. According to EISA, corn-based ethanol is to be capped at 15 billion gallons. In order to produce the additional 16 billion gallons of cellulosic ethanol, new facilities will have to be built that are scaled to produce sufficiently large quantities in order to sustain profitable enterprises. Going hand-in-hand with the production of ethanol will be the need for more flexible-fuel vehicles (FFVs) that can burn ethanol up to a level of 85 percent.

The Energy & Environmental Research Center has worked with all facets of the ethanol industry: from siting corn ethanol plants, to developing new fermentation schemes, to inventing new thermochemical processes that require absolutely no fermentation. So here's an answer to a question we get asked at least weekly-what is the status of this ethanol revolution? Indeed, it will take a revolution.

With respect to FFVs the automakers seem willing to produce more E85 FFVs, but in most states gas stations that carry E85 lag way behind and there is still a severe lack of public acceptance and incentive to get consumers interested in FFVs. Of the 7 million or so E85 vehicles on the road, GM has made half of them and has plans for 50 percent of its production to be FFVs by 2012.

With respect to the fuel production side, the U.S. DOE is trying to stimulate technology development for cellulosic ethanol plants. Within the past two years, DOE has provided awards to 20 organizations working to develop such technologies. Currently, 19 of the original 20 organizations are actively working toward their goals; one organization has dropped out; and three are producing cellulosic ethanol-albeit at small scales. The array of technologies being developed is diverse, in part due to the wide variety of cellulosic biomass feedstocks being utilized.

Most ethanol plants today are located in the Corn Belt of the U.S., but most of the 19 organizations with DOE awards for cellulosic ethanol are developing their technology outside of the Corn Belt. This represents the diversification of feedstocks being developed. States that currently do not possess starch-ethanol production facilities and are hosting a DOE-funded project include Maine, Vermont, Florida, Montana and Louisiana.

The technologies used to convert cellulose to fermentable sugars include biological methods that utilize concentrated acid hydrolysis and enzymatic hydrolysis, coupled with fermentation. Other technologies will utilize thermochemical means such as gasification to convert the biomass to gas and then reform that gas using chemical catalysis or biological fermentation to produce ethanol. When compared head-to-head, these various technologies offer an almost endless combination of possibilities for conversion of cellulose to ethanol.

In conclusion, the status of the cellulosic ethanol revolution is that automakers are poised to do their part, consumers are lagging a bit in motivation, and technology options have yet to be proven commercially. Whether this is sufficient to meet the EISA goals remains to be seen.


Paul Pansegrau is a research scientist at the EERC. Reach him at ppansegrau@undeerc.org or (701) 777-5169.