Biofuel Blues

The United States isn’t running short on corn–just visit any state fair or backyard barbecue. But while corn on the cob abounds, there might not be enough of this and other crops to feed rising demand for biofuel production, scientists say. A satellite analysis of total plant growth in the lower 48 states opens up new doubts about whether U.S. growers can reasonably meet steep Congressional quotas for ethanol production by 2022.

In 2007, the nation’s eyes turned to corn. Or, at least, its potential for making ethanol, an alternative to traditional gasoline. That year, Congress passed the Energy Independence and Security Act of 2007 (EISA). The legislation mandated that the domestic energy sector increase its yearly production of ethanol–often made from corn or other plants–from 40 billion to 136 billion gallons. It’s an ambitious goal, but, many scientists soon realized, maybe not an achievable one.

Kolby Smith of the University of Montana and colleagues set out to gauge just how ready the U.S. is to meet Congress’ requirements. And they did it from the skies. The team used satellite images to map vegetation, from agricultural fields to forests and minimally grazed rangeland, across the country, creating a full catalog of leafy and woody resources. Then, they estimated how much biofuel could reasonably be squeezed out of those plants.

The picture doesn’t look pretty for EISA, Smith’s team reports in Environmental Science & Technology. Theoretically, there’s enough plant power to go around. The team’s estimates suggest that dedicated growers in the U.S. could reap a whopping 22.2 exajoules of energy stored in vegetation, from corn to sagebrush, each year–more if they don’t mind harvesting plants from national parks. That’s more than enough vegetation to fill EISA’s steep quotas. But getting to all that potential would be a monumental undertaking. In other words, farmers would need to expand into unexploited rangeland, sowing then harvesting plants from an area three times bigger than the U.S.’s total existing croplands. As an alternative, ethanol producers could buy up around 80% of the annual supply of corn, wheat and other crops currently grown in the U.S. – but diverting that much of the harvest that could cause problematic ripples in the economy and food supply.

In all, the group argues, EISA doesn’t make a lot of economic sense, especially since increased agriculture would bring problems of its own, including increased fertilizer usage. Daniel Strain | March 7, 2012

Source: W.K. Smith et al. (2012). Bioenergy Potential of the United States Constrained by Satellite Observations of Existing Productivity. Environmental Science & Technology. DOI: 10.1021/es203935d.

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