GM: Non-Grain Ethanol at $1 Per Gallon

Ethanol is viewed as a promising way to reduce our dependence on imported oil. In fact, the new Energy Independence and Security Act calls for a large increase in biofuels from 7.5 billion gallons in 2012 to 36 billion gallons in 2022. Corn- and other grain-based ethanols could account for up to 15 billion gallons of these biofuels. Unfortunately, biofuels have to compete with use of the same grains for food. As we are already seeing, this means higher food prices and even food shortages.

The answer is cellulosic ethanol made from the cellulose that's present in every plant. Unlike grain-based ethanol, the whole plant can be used and not just the grain, which means greater ethanol yield per acre. Also, waste materials discarded every year - like urban wood waste, mill residues, corn stover, and wheat straw - could create enough ethanol to meet as much as 30 percent of U.S. fuel needs.

General Motors is getting into the cellulosic ethanol production business. Recently, it joined with Coskata Inc. and Mascoma Corp. to further develop these companies' cellulosic ethanol production technologies. This works well with GM's alternative fuel strategy since GM has built over three million flexible-fuel vehicles (FFVs) to date that can run on either gasoline or E85 ethanol, more than any other automaker. About seven million FFVs are now operating on U.S. roads.

Coskata uses a three step syngas-to-ethanol process to produce ethanol from many feedstocks including garbage, old tires, and plant waste. This process would allow waste and non-recyclable vehicle parts from GM manufacturing facilities to be used for creating ethanol. Here, carbon-based feedstock are converted into syngas by gasification, and then Coskata's proprietary microorganisms convert the syngas into ethanol by consuming the carbon monoxide (CO) and hydrogen (H2) in the syngas. Finally, what Coskata calls its "pervaporation technology" separates and recovers the ethanol.

The process requires no additional chemicals or pre-treatments. The microorganisms also ferment the material at lower temperatures and pressures to further reduce costs, which is projected to be a rather amazing $1 per gallon. Importantly, Coskata's process answers the environmental and energy concerns often posed by those opposed to ethanol as a motor fuel. The process uses less than a gallon of water to make a gallon of ethanol compared to three gallons or more of water consumed with other processes. Plus, for every unit of energy used, it generates up to 7.7 times that amount of energy. This compares to an energy ratio of only about 1.3 for grain-based ethanol. It also reduces CO2 emissions by up to 84 percent on a full well-to-wheels basis compared to gasoline.

Coskata will have a pilot plant in operation by the end of 2008. GM will use the fuel produced here for testing vehicles at GM's Milford Proving Grounds. Coskata expects to have its first commercial-scale plant with an annual capacity of 50 to 100 million gallons of ethanol running in 2011.

The second part of GM's cellulosic ethanol effort involves Mascoma Corp. and its Consolidated Bioprocessing (CBP) technology. This single-step biochemical conversion of non-grain biomass into low-carbon alternative fuels uses a single microorganism or group of organisms to break down plant matter in the conversion process. This lowers costs by limiting the additives and enzymes compared to those used in other biochemical processes. Mascoma's CBP process consists of a mild pretreatment followed by the introduction of cellulose-utilizing and ethanol-fermenting microbes that both hydrolyze and ferment the sugars into ethanol.

Mascoma is testing its CBP technology and expects to begin producing ethanol later this year at its demonstration plant under construction in Rome, N.Y. Mascoma also has partnered with The University of Tennessee to develop a switchgrass-to-ethanol pilot facility near Knoxville.