Monday, October 25, 2010

A Tale of Two Fuels from One Feedstock

By Daniela Sciaky, Ph.D.

One problem associated with the production of biofuels from a first-generation feedstock is the un- or under-utilization of the waste products associated with production of that fuel. Scientists at the Universidade Federal de Viçosa in Brazil collaborating with scientists at Iowa State University report in the October 9th online version of Biomass and Bioenergy that cellulosic waste remaining after the extraction of oil from first generation feedstocks can be used for ethanol production. The ethanol in turn can be used to meet the transesterification demand of the oil for biodiesel production.

Feedstocks tested include soybean, sunflower, Jatropha curcas, palm kernel, castor bean, and cottonseed. After oil extraction, palm biomass yields 108 m3 per km2 (approximately 191.6 gallons per acre) of cellulosic ethanol, the highest potential ethanol yield of any of the crops studied based on Brazilian crop yields. Second is Jatropha curcas, with an ethanol yield of 40 m3 per km2 or approximately 71 gallons per acre. In comparison the US Department of Agriculture estimates that 180 gallons of ethanol can be produced from one acre of harvested corn stover or 5,500 pounds of dry corn stover. Potentially a total of 3.5 hm3, or 922 million gallons of ethanol, could be produced from soybean oil extraction co-products from Brazil.

The results of this research provide an example of where waste biomass becomes extremely useful. Waste palm biomass remaining after oil extraction can yield more ethanol per acre than harvesting corn stover. In actuality a lot of the corn stover must be retained in the field in order to maintain the integrity of the soil. Therefore production of ethanol from the waste products of other biofuel production holds great promise.

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