A new idea to derive ethanol from waste material like grass, wood pulp, animal waste, and garbage into ethanol has been devised by researchers at the U.S. Department of Energy's Ames Laboratory and Iowa State University.
Their hunch is that combining the process of gasification-which turns carbon-based feedstocks under high temperature and pressure in an oxygen-controlled atmosphere into synthesis gas (syngas)-with high-tech nanoscale porous catalysts may make it possible to create ethanol from a wide range of biomass.
Syngas is made up primarily of carbon monoxide and hydrogen, and smaller quantities of carbon dioxide and methane.
The researchers describe gasification as the same technique that was used to extract the gas from coal that fueled gas light fixtures prior to the advent of the electric light bulb.
According to them, the advantage of gasification compared to fermentation technologies is that it can be used in a variety of applications, including process heat, electric power generation, and synthesis of commodity chemicals and fuels.
"There was some interest in converting syngas into ethanol during the first oil crisis back in the 70s. The problem was that catalysis technology at that time didn't allow selectivity in the by-products. They could produce ethanol, but you'd also get methane, aldehydes and a number of other undesirable products," said Ames Lab chemist and Chemical and Biological Science Program Director Victor Lin.
Studying the chemical reactions in syngas conversion, Lin found that the carbon monoxide molecules that yielded ethanol could be "activated" in the presence of a catalyst with a unique structural feature.
"If we can increase this 'activated' CO adsorption on the surface of the catalyst, it improves the opportunity for the formation of ethanol molecules. And if we can increase the amount of surface area for the catalyst, we can increase the amount of ethanol produced," Lin said.
Lin and his colleagues looked at using a metal alloy as the catalyst.
For increasing the surface area, the researchers used nano-scale catalyst particles dispersed widely within the structure of mesoporous nanospheres, tiny sponge-like balls with thousands of channels running through them.
The total surface area of the dispersed catalyst nanoparticles was roughly 100 times greater than the surface area one could get with the same quantity of catalyst material in larger, macro-scale particles.
Robert Brown, the director of ISU's Center for Sustainable Environmental Technologies (CSET), said: "Gasification to ethanol has received increasing attention as an attractive approach to reaching the Federal Renewable Fuel Standard of 36 billion gallons of biofuel."
Lin added: "The great thing about using syngas to produce ethanol is that it expands the kinds of materials that can be converted into fuels. You can use the waste product from the distilling process or any number of other sources of biomass, such as switchgrass or wood pulp. Basically any carbon-based material can be converted into syngas. And once we have syngas, we can turn that into ethanol."