Back to the future: Prairie grasses emerge as rich energy source. ‘With shrinking glaciers and other signs of global warming upon us, the search is on for alternative fuels to stem the release of greenhouse gases such as carbon dioxide into the atmosphere.
This week a new contender burst on the scene: diverse mixtures of native prairie grasses. A University (of Minnesota) team led by David Tilman, Regents Professor of Ecology, found that these grasses yield more net energy than either ethanol from corn or “biodiesel” fuel from soybeans. Grass-based fuel can even lead to a net decrease in atmospheric carbon dioxide, whereas ethanol and biodiesel increase it.
The study is based on 10 years of work at the University’s Cedar Creek Natural History Area. Written by Tilman, postdoctoral researcher Jason Hill and research associate Clarence Lehman, it is the cover story in the Dec. 8 issue of the journal Science.
For many years, renewable fuels from plants (“biofuels”) have been seen as beacons of hope because the carbon dioxide released in burning them can be absorbed by the next year’s crop. But in a report earlier this year, Tilman, Hill and others showed that corn grain ethanol and soy biodiesel do little to offset carbon dioxide emissions because it takes so much fossil fuel to produce them.’
Ethanol fuel presents a corn-undrum. ‘Five University ((of Minnesota) researchers have taken a stand in the long-running debate over whether ethanol from corn requires more fossil fuel energy to produce than it delivers.
Their answer? It delivers 25 percent more energy than is used (mostly fossil fuel) in producing it, though much of that 25 percent energy dividend comes from the production of an ethanol byproduct, animal feed.
But the net energy gain is much higher – 93 percent – from biodiesel fuel derived from soybeans. And alternative crops such as switchgrass or mixed prairie grasses, which can grow on marginal land with minimal input of fossil fuel derived fertilizers and pesticides, offer the best hope for the future.’