|Enzymatic Hydrolysis and
Fermentation of Broken Rice
Kernels and Rice Straw - 2007
Project Leader and Principal Investigators
Kevin Holtman,research chemist, USDA/ARS, Albany, CA
This new project is investigating the potential for rice straw and broken
rice kernels to be used as feedstock to produce “green” biofuels. This work
is part of a larger project determining the economic feasibility of mixed
feedstocks in biorefinery production.
In the first year of the project, material under study included municipal solid waste (MSW) and rice straw collected and baled during the 2005 harvest. In one set of experiments, ground up MSW and rice straw were pretreated with liquid hot water under pressure. An enzyme solution was used in the pretreatment. Enzyme hydrolysis followed the pretreatment.
The results showed that the liquid hot water pretreatment significantly increases the conversion of MSW or ground rice straw into ethanol with only modest increases in energy requirements. Researchers also assessed different times and temperatures to find the optimal pretreatment conditions.
Enhancing the yield of ethanol from rice straw with pretreatment improves its economic feasibility as a biofuel. Use of MSW as the “platform” feedstock provides a consistent substrate, helping to justify capital expenditure and thereby making the use of rice straw more economically feasible. Based on the first year’s findings, rice straw does hold promise as a substrate in a mixed feedstock biorefinery.
Future work will focus on optimizing liquid hot water pretreatment of rice straw, as well as an examination of broken rice kernels and commingled kernels with MSW for pretreatment.
An existing one- to two-ton batch autoclave near Salinas will be expanded in the near future to an operating, integrated pilot-scale biorefinery. A demonstration plant at a landfill near Salinas is also being planned.