Enzymatic Hydrolysis & Fer-mentation of Broken Rice Kernels and Rice Straw - 2008

 

 

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Project Leader and Principal  Investigators

Kevin Holtman, research chemist, USDA/ARS, Albany, CA

 

This is the second year for a project investigating the potential for rice straw to be used as a feedstock in an integrated biorefinery under development by the U.S. Department of Agriculture. Experimental results and economic analyses thus far support the use of rice straw in prototypical systems. Use of broken rice kernels does not appear as promising.

Municipal solid waste (MSW) is the base feedstock material for the biorefinery in this project. MSW shifts the burden of justification for capital expenditure away from seasonal crops to a reliable, low-cost substrate. It also creates an option for alternative disposal methods of agricultural byproducts such as rice straw.

Experiments were conducted with rice straw from M-202 rice grown near Williams in 2006. Broken rice kernels, also from M-202, were supplied by the Rice Experiment Station.

The rice straw was subjected to a hot water pretreatment to help accelerate the fermentation process used to produce ethanol. Observations indicate degradation of the cellulose in the rice straw occurred effectively. A preliminary breakdown of experimental data shows that under a best-case scenario, 1,000 tons of rice straw a day could generate 37,000 gallons of ethanol with gasification and anaerobic digestion. Thatís enough energy to offset 22,000 gallons of gasoline. The energy produced would be enough to break even or prove slightly profitable.

The experiment showed that rice straw as a stand-alone will not produce enough energy to heat the biorefinery process. It would be best utilized incorporated as additional capacity to the baseline MSW for ethanol production.

Research on broken rice kernels showed that they can be converted to ethanol. However, because of concerns about the development of liquid transportation fuels from food starch sources, this work has been minimized.

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