GM has announced that it has entered into a second partnership to develop second generation biofuels.

The latest relationship is with Mascoma Corp, which has developed a single-step biochemical process to convert non-grain biomass into biofuel. GM has made an undisclosed equity investment in the company.

In January this year GM took a stake in another second generation biofuel company, Coskata Inc. That uses a thermo-chemical process to produce ethanol from non-grain sources.

"Taken together, these technologies represent what we see as the best in the cellulosic ethanol future and cover the spectrum in science and commercialization," GM President Fritz Henderson said. "Demonstrating the viability of sustainable non-grain based ethanol is critical to developing the infrastructure to support the flex-fuel vehicle market."

GM has invested heavily in flex-fuel vehicles that can run on gasoline or E85 ethanol, or a combination of the two. Of seven million flex-fuel vehicles on the road in the US, three million were produced by GM.

GM said that Mascoma's single-step cellulose-to-ethanol method, called Consolidated Bioprocessing, or CBP, lowers costs by limiting additives and enzymes used in other biochemical processes. Based in Boston, privately held Mascoma is using proprietary microorganisms and is collaborating with research partners globally to identify and patent additional biomass-to-ethanol technologies.

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

GM's involvement with Mascoma will include projects to evaluate materials and other fuels for specific engine applications as well as collaborating on Mascoma's efforts to expand its commercialisation projects globally, including promotion of increased biofuels distribution.