The process involves the use of nanotechnology and gasification to convert carbon-based materials into a product called synthesis gas, or syngas, which in turn can be made into ethanol.
Developing new ways of producing biofuels such as ethanol is urgent business as the country and world scout for alternatives to fossil fuels.
For now, ethanol is made chiefly by fermenting corn, diverting the valuable commodity from serving as food for people and livestock.
"The great thing about using syngas to produce ethanol is that it expands the kinds of materials that can be converted into fuels," said Victor Lin, director of the Chemical and Biological Science Program at the U.S. Department of Energy's Ames Laboratory."
"You can use the waste product from the distilling process or any number of other sources of biomass, such as switchgrass or wood pulp," Lin said in a statement.
"Basically any carbon-based material can be converted into syngas," he said. "And once we have syngas, we can turn that into ethanol."
Ames scientists, working with colleagues at Iowa State University, are employing gasification to make syngas.
To make the gas, they subject carbon-based feedstocks to high temperature and pressure in an oxygen-controlled atmosphere.
North Dakota Gasification Great Plains Synfuels Plant (Photo courtesy U.S. DOE)
Gasification is not a new technology but has been around since the 1800s, when it was used to extract gas from coal to produce fuel for lighting and cooking.
The attempt to turn syngas into ethanol also is not new. Scientists have been researching the process for 90 years, according to a study published in January in "Energy & Fuels," a journal of the American Chemical Society.
"There was some interest in converting syngas into ethanol during the first oil crisis back in the ‘70s," Lin said, but there was a problem. "They could produce ethanol, but you'd also get methane, aldehydes and a number of other undesirable products."
The fault lay with the catalysts, materials that promote and speed chemical reactions without themselves being changed.
Lin and his colleagues hit upon using as catalysts invisibly small nanoparticles of a metal alloy.
The nanoscale is almost inconceivably small. A nanometer - one billionth of a meter - is about the size of 10 hydrogen or five silicon atoms, and the width of a human hair is about 80,000 nanometers.
Ames Laboratory describes the catalyst nanoscale particles as having thousands of channels running through them, which increases the amount of catalytic surface area 100-fold over ordinary-sized catalysts.
"If we can increase the amount of surface area for the catalyst, we can increase the amount of ethanol produced," Lin explained.
While nanotechnology offers a solution to the catalyst problem, gasification is another technology that is required to produce ethanol from garbage.
Private industry is chasing the syngas-to-ethanol goal, as well, and employing gasification to do it.
The company Coskata Inc., in partnership with General Motors, is building a $25 million demonstration plant near Pittsburgh, Pennsylvania, where it plans to make ethanol from woody biomass, and farm and industrial wastes.
The company's goal is to produce ethanol from non-food-based sources for less than $1 a gallon.
On its website, Coskata says the company uses a combination of gasification and fermentation to convert carbon-based wastes into syngas, and then into ethanol.
The pilot plant is designed to produce 40,000 gallons of fuel a year. The company said it plans to complete a full-size plant capable of producing 50 million to 100 million gallons of fuel a year by 2011.
To control the chemical makeup of the syngas for reliable operation and high-quality, researchers at the Center for Sustainable Environmental Technologies, or CSET, at Iowa State have developed fluidized bed gasifiers. The gas produced can be used in a range of applications from replacing natural gas in grain ethanol plants to providing hydrogen for fuel cells.
CSET director Robert Brown says, "Gasification to ethanol has received increasing attention as an attractive approach to reaching the federal Renewable Fuel Standard of 36 billion gallons of biofuel."
Authorized by the Energy Policy Act of 2005, the federal Renewable Fuels Standard calls for the production of 36 billion gallons of biofuels annually by 2022.
Of this, roughly 16 billion gallons is expected to be from cellulosic biofuels, derived from woody biomass - plant sources such as trees and grasses.
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