U.S. Department of Agriculture (USDA) researchers are working turning barley straw and corn stover into biobutanol. This article from USDA’s Agricultural Research Service (ARS) says the agricultural by-products could be a cost-effective feedstock for the green fuel.
Gallon for gallon, butanol has 30 percent more energy than ethanol and only around 4 percent less energy than a gallon of petroleum-based gasoline. [ARS chemical engineer Nasib] Qureshi has confirmed that both barley straw and corn stover can be converted to butanol via separate hydrolysis, fermentation, and recovery (SHFR) or by simultaneous saccharification, fermentation, and recovery (SSFR). In SSFR, releasing the plant sugars, fermenting them to butanol, and recovering the butanol are combined into a single operation that is performed in a single reactor.
In a recent study, Qureshi’s team used a process called gas stripping to “harvest” butanol fermented during SSFR. They obtained a final butanol yield that was 182 percent of the yield obtained from a control study that used glucose.
Using the same protocols, the scientists were able to ferment over 99 percent of the sugars in pretreated corn stover. This resulted in butanol yields that were 212 percent greater than yields observed from the controls, and 117 percent greater than the butanol yields from the barley straw.
In the corn stover-to-butanol process, the researchers are using vacuum technology instead of gas stripping to simultaneously recover butanol during fermentation. This new process released more than 97 percent of the stover sugars, making them available for fermentation.