Almost any kind of plant material can be used as a feedstock to make ethanol. To date, most ethanol comes from sugar- and starch-based feedstocks because processing is relatively cheap and easy. Unfortunately, it also means producing fuel from crops that are ordinarily used for food, such as corn.
An alternative is cellulosic ethanol, which comes from the cellulose in wood, straw, crop residues and other non-edible plant matter. There are plant species – such as switchgrass in North America – that grow readily in poor soil and climate conditions, yet yield far more feedstock per acre than any food crop. They also require much less energy to cultivate successfully. With respect to overall energy balance, cellulosic feedstocks like switchgrass are far superior to corn for ethanol production.
The sticking point so far has been the cost of producing ethanol. At present, it is about 40% more expensive to get ethanol from cellulosic feedstock than from corn. But a recent industry survey predicts that this cost difference will be erased by 2016.
In the meantime, there is increasing development in Europe of a different cellulosic feedstock: Arundo donax, commonly known as Giant Cane or Giant Reed. These 25-foot tall bamboo-like plants are an ancient species that may have been the reeds that hid baby Moses along the Nile River. Amazingly, they can yield three times as much biomass per acre as switchgrass.
Giant Reed is still awaiting EPA approval as a renewable fuel feedstock. In managed settings it holds promise as a biomass solution – so long as we can prevent it from escaping and becoming another kudzu-like invasive species.
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Web Links
Cellulosic ethanol heads for cost-competitiveness by 2016
http://about.bnef.com/press-releases/cellulosic-ethanol-heads-for-cost-competitiveness-by-2016/
Ethanol Feedstocks
http://www.afdc.energy.gov/fuels/ethanol_feedstocks.html
Arundo Is Better than Switchgrass for Biomass Power Generation
Photo, taken on March 17, 2009, courtesy of Matt Lavin via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY, with partial support from the Field Day Foundation.