August 14, 2007 4:00 AM PDT
Cellulosic ethanol: A fuel for the future?
As the biomass program manager for the Georgia Forestry Commission, Dartnell is impatiently waiting for construction to begin next month of a plant that will convert forestry wastes into ethanol, a car fuel.
The facility is an important test to see whether lumber and agricultural by-products, rather than corn or sugar cane, are an economically viable "feedstock" for ethanol production. Behind the plant is Range Fuels, a start-up headed by a former Apple executive and financed by famed Silicon Valley venture capitalist Vinod Khosla.
Dartnell hopes this project, eligible for up to $76 million in U.S. Department of Energy grants, will lead to many more plants--and a new industry--in the state.
"This gives us energy security and it keeps all the money in-state," said Dartnell. "Today, if we buy a tank of gasoline, a lot of money ends up with the oil reserve owners and refiners, and it's spread all around the world."
Georgia's enthusiasm for the Range Fuels plant--one of a handful now being planned in the U.S.--underscores the high hopes attached to cellulosic ethanol, an advanced biofuel that backers anticipate will play a large role in meeting federal targets for domestic fuel production that can one day offset reliance on foreign oil.
But like many energy-related technologies now being actively pursued, there are potential pitfalls for advanced biofuels, including long-standing technology hurdles and environmental questions. And getting clear-cut answers on the benefits and trade-offs of biofuels is tricky.
"Just because the technology can be done right doesn't mean we will use it right or develop it in a smart way; that's the real challenge," said Nathanael Greene, senior policy analyst at the National Resources Defense Council (NRDC). "Biofuels, in particular, can be anywhere from very good for the environment to very bad."
Grain versus cellulose
Cellulosic ethanol promises several advantages over corn-based ethanol which, fueled by government policies and investor capital, is now undergoing a massive build-out.
Making ethanol from forestry or agricultural waste does not involve the same intensive farming as corn, which requires more water and labor, cellulosic ethanol proponents say. Also, in the ongoing food-versus-fuel debate, cellulosic ethanol advocates say that forests don't compete for land with food crops.
The Soperton, Ga., plant will be using wood cast away by loggers. Trees are hauled to a central point where their tops and branches are cut off, providing the material for Range Fuels' multi-step thermochemical process.
Tree branches will go into a large tank where enough heat and pressure are applied to the mix to turn it into a gas. That synthetic gas is treated and then passed through a chemical catalyst which converts the gas to alcohol. Finally, the alcohol gas is converted to fuels and then turned into liquid.
Companies are pursuing different routes to cellulosic ethanol. Iogen, one of several companies using enzymatic processes, has built a demonstration plant in Ottawa that uses specially designed enzymes to convert agricultural wastes, such as corn stalks and straw, to ethanol.
Other wood wastes, even wood from natural disasters and fires, could be used, Dartnell said. Researchers are also busy devising processes to convert grasses, such as switchgrass and Micanthus, into fuels.
"Everybody is looking for feedstocks which they have to then plant and grow," Dartnell said. But because current logging practices usually leave branches behind, the waste is already there. It's just not being put to good use.
Indeed, companies have promised working cellulosic ethanol processes for years, but at this point, most work remains in the research or trial stage.
Part of what has held back making advanced biofuels from wood or straw is the significantly higher capital costs it takes to build a plant. But even with the bigger up-front investment required, rising corn prices have made the cost of biofuel from cellulosic sources only slightly higher than corn-based ethanol, according to a recently published report in the journal Biofuels, Bioproducts and Biorefining.
Range claims its first plant will be completed next year and will be capable of making 20 million gallons of ethanol a year. It intends to later expand to 100 million gallons per year.
Dartnell estimates that the state has enough wood residue from tree farming and milling to create 2 billion gallons per year.
75 commentsJoin the conversation! Add your comment