Cellulosic Ethanol Using Gasification-Fermentation

RedOrbit.com
Posted on: Sunday, 21 September 2008, 03:00 CDT
By Huhnke, Raymond L

The push for the United States to produce more biofuels was reinforced by the recent amendment to the 2005 Renewable Fuels Standard, setting a new target of 136 billion L (36 billion gal) by 2022. Cellulosic biofuels will play a major role in reaching this goal. For nearly a decade, the multidisciplinary biofuels research team led by Oklahoma State University (OSU) has been investigating a gasification-fermentation process in which low-cost, under-utilized biomass, such as perennial grasses and crop residues, is converted to ethanol and other value-added products. A holistic approach is being employed, addressing the more critical issues along the continuum from biomass production to liquid fuel generation. In this bioconversion process, the total biomass including lignin is utilized, which can result in high energy conversion efficiency.
The process begins with biomass gasification where, under a controlled oxygen supply, cellulose, hemicellulose, and lignin are converted to a producer gas, primarily CO, CO2, and H^sub 2^. The producer gas then flows through a cleaning and cooling system and is subsequently directed to a bioreactor. The gas is bubbled through the bioreactor where microorganisms (acetogens) convert the gas into ethanol and other value-added products. The mixture is further processed to separate and recover these products.

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