The prolonged California drought, made worse by climate change, should get farmers and regulators thinking more about the benefits of cellulosic ethanol. Plants whose sugars are fermented from cellulose, as opposed to starchy plants used for food like corn and sugar cane, often don’t need nearly as much water, tending or high-quality soil.
Currently, the vast majority of the 14 million gallons of ethanol produced in the United States is made from corn — not “corn on the cob,” the sweet corn consumed by humans, but field corn normally given to livestock. Because of the vast scale of corn production, growers are able to tinker and experiment, and their advances in technology and growing techniques have brought higher crop yields than ever: In 2014 farmers grew an average of 171 barrels per acre, about 6 barrels per acre more than the record yield of 2009.
That translated to yields of ethanol: According to the Renewable Fuels Association, corn used for fuel yielded 2.82 gallons per bushel, or 478.8 gallons per acre.
Other starchy, food-based fuel crops are not far behind: Sugar beets actually produce more than twice the ethanol yields as corn (about 1,200 gallons per acre), and many U.S. farmers are increasing production. Grain sorghum is another good sugar/starchy ethanol “feedstock,” yielding potentially 2.27 gallons per bushel.
Other examples of cellulosic ethanol feedstocks would be switchgrass; corn stover; miscanthus giganteus; and wood waste left over from forestry operations. These sources not only are inedible for humans, they don’t require that much work to grow: In the case of corn stover, it’s the leftovers from corn harvesting.
For more information, check out our cool new shareable infographic on feedstocks for ethanol:
According to a study released in March by the Energy Biosciences Institute at the University of Illinois, miscanthus — a reedy plant that can grow 12 feet tall or more — was the “clear winner” in a side-by-side comparison between switchgrass and corn stover, when it comes to yields and costs of production.
“One of the reasons for interest in these second-generation cellulosic feedstocks is that if they can be grown on low-quality soil, they wouldn’t compete for land with food crops, such as corn. This study shows that although miscanthus yield was slightly lower on marginal, low-quality land, a farmer would have an economic incentive to grow miscanthus on the lower quality land first rather than diverting their most productive cropland from growing corn,” said University of Illinois agricultural economist Madhu Khanna, a co-author of the study.
If the California drought persists for years, and the situation is repeated around the world, it makes sense to displace dirty oil with cleaner-burning alcohol fuels, especially ones that thrive in arid conditions.
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