Will Cellulosic Ethanol Take Off?

Fuel from grass and wood chips could be big in the next 10 years--if the government helps.

By Kevin Bullis

ALCOHOL FUEL: Celunol, based in Cambridge, MA, tests its cellulosic-ethanol process in this pilot-scale plant, which converts biomass such as switchgrass into ethanol. Biomass is stored and handled in the building to the right. From there it’s fed into the four black tanks in the center, which contain enzymes for breaking down cellulose and other complex carbohydrates to form simple sugars that can be fermented in the “beer” tank below. There, the liquid produced has the same alcohol concentration as beer. Next, the beer is distilled in the tall column left of center before being stored in ethanol tanks at left. Celunol started construction on a much larger cellulosic-ethanol plant this month.

Credit: Courtesy of Celunol Corp.

Cellulosic ethanol, a fuel produced from the stalks and stems of plants (rather than only from sugars and starches, as with corn ethanol), is starting to take root in the United States. This month, Celunol, based in Cambridge, MA, broke ground on an ethanol plant in Louisiana that will be able to produce 1.4 million gallons of the fuel each year starting in 2008. Other companies are moving forward as well with plans to build plants.

But experts from industry and environmental groups say that without loan guarantees and other incentives, the nascent industry will fail to emerge from the current demonstration phase to produce commercial-scale quantities of ethanol. And without that, it may be impossible to meet President Bush's ambitious goal of producing 35 billion gallons of renewable fuels a year by 2017.

Cellulosic ethanol is attractive because the feedstock, which includes wheat straw, corn stover, grass, and wood chips, is cheap and abundant. Converting it into ethanol requires less fossil fuel, so it can have a bigger effect than corn ethanol on reducing greenhouse-gas emissions. Also, an acre of grasses or other crops grown specifically to make ethanol could produce more than two times the number of gallons of ethanol as an acre of corn, in part because the whole plant can be used instead of just the grain. That's good news because many experts estimate that corn-ethanol producers will run out of land, in part because of competing demand for corn-based food, limiting the total production to about 15 billion gallons of fuel. (Already, corn-ethanol plants--existing and planned, combined--have a capacity of about 11 billion gallons.) The greater productivity of cellulosic sources should eventually allow them to produce as much as 150 billion gallons of ethanol by 2050, according to a report by the National Resources Defense Council (NRDC). That's the equivalent of more than two-thirds of the current gasoline consumption in the United States.

But it will take some time to reach these levels of production. Even producing enough cellulosic ethanol to meet the president's 35-billion-gallon goal will be difficult. That will require that roughly 15 billion gallons would come from non-corn-grain sources such as cellulosic ethanol (about 5 billion gallons might come from biodiesel culled from oils in crops such as soybeans). And reaching 15 billion gallons by 2017 will be a challenge. Currently, according to the ethanol industry's list of producers in the United States, none of the ethanol comes from cellulosic biomass.

Cellulosic-ethanol companies are hopeful that they can meet this goal. Colin South, the president of Mascoma Corporation, also based in Cambridge, says that if all goes well, cellulosic ethanol could supply half of the 35-billion-gallon goal by 2017. But so far Mascoma has only announced plans to build a demonstration facility with a capacity of about half a million gallons of fuel per year. That facility should be ready in 18 months, South says. But as is the case with the new Celunol plant, the facility's primary purpose would be to demonstrate that the company's technology can work at a large scale; it will not always operate at full capacity, as the system is used to test new cost-saving technologies.