Cleantech.com has a look at cellulosic ethanol company Coskata and their "semi-commercial" demonstration plant - Deep dive in Coskata’s bacteria-based ethanol.
Coskata’s process is a cross between enzymatic hydrolysis to decompose feedstock into sugars and ferment to create alcohol, and thermochemical, in which gasification is followed by reaction with a man-made catalyst to create ethanol.
“These are all based on good science, sound science, but there’s inherent flaws with both of those and we’ve tried to take the best of both,” Roe said.
Roe said the process is net energy positive, but he declined to specify how much excess energy is produced. The process is low temperature and low pressure, which reduces operating costs, he said.
Roe said Westinghouse’s process also harnesses excess heat energy liberated during the gasification process.
Alter NRG’s Chief Marketing and Sales Officer Richard Fish said the plasma gasification technology is very efficient, retaining 80 percent of the energy in the feedstock in the process.
The 8,000-degree Fahrenheit plasma torch uses 2 percent to 5 percent of the system’s energy input.
Coskata says Argonne National Laboratory vetted its process in late 2007 and early 2008, concluding it offered a 96 percent reduction in greenhouse gases compared to traditional petroleum fuel. By comparison, sugarcane ethanol offers a 78 percent reduction, Roe said.
More at Technology Review - Commercializing Garbage to Ethanol
The plant has the capacity to produce tens of thousands of gallons of ethanol a year, which is a significantly smaller scale than the 20 million or more needed for a commercial plant, says Wesley Bolson, Coskata's chief marketing officer and vice president of government affairs. But it will use the same equipment that would be used at a commercial plant, he says. For example, it will use bioreactors--in which microorganisms produce ethanol in low concentrations--that are the same size as would be used in a commercial plant, only fewer in number. The company, which has partnered with General Motors, hopes that demonstrating its equipment will help it finance a 55-million-gallon commercial plant that has already been designed, he says.
Coskata is one of several companies developing processes to make cellulosic ethanol, which is made from wood chips and other cellulosic materials and can be produced using less fossil fuel than ethanol made from corn. The U.S. Federal Renewable Fuels Standard requires the use of cellulosic ethanol, starting with 100 million gallons next year and increasing to 16 billion gallons by 2022. But so far no commercial plants have been built, in part because financing has been hard to come by, according to the Biotechnology Industry Organization (BIO). BIO estimates that next year about 7 million gallons of cellulosic ethanol will be produced at demonstration plants. The first commercial-scale plants, including Coskata's, are expected to open in 2012, when the fuels standard requires the production of 500 million gallons of cellulosic ethanol.