Biofuels have gotten a lot of press as the answer to both global warming and to our dependence on foreign oil. In a well-written and -researched piece in New Scientist magazine, Fred Pearce warns us that the silver clouds of corn-based and sugar-based biofuels both have dark linings. Right idea, but we aren’t there yet.
Bioethanol is made from processing either starchy plants (like corn) or sugar-rich plants (like sugar cane). With corn, you first have to pre-process it to turn the starches into sugar, then the corn sugar or cane sugar is fermented and distilled to produce ethanol. Using biofuels instead of fossil fuels greatly reduces the emissions of greenhouse gases from an automobile. Good so far.
Trouble is, it takes a fair amount of fossil fuel to produce the corn-based ethanol due to that pre-processing step, not to mention the fertilizers and tractor fuel used in growing the corn in the first place. Study results vary depending on their assumptions, but the upshot is that if you look at the entire process, it’s not clear that corn-based ethanol is much of a leap forward, environmentally speaking. Then there’s the fact that it takes a lot of land to grow the corn: it’s estimated that if the U.S. turned its ENTIRE corn crop into ethanol, we’d meet about 10% of our fuel demand. And a lot of people around the world would go hungrier. There are already signs of a shortage of corn and a spike in prices worldwide as a result of the so-far modest demand for corn-based ethanol.
Sugar-based ethanol has its own problems. Although the ratio of greenhouse gases saved vs. used in the production is much higher, it also requires a lot of land and the fear is that tropical developing countries will clear-cut more forests to get that land, which will make global warming worse. Sugar growing is also very water-intensive, and fresh water is another non-renewable resource that’s getting scarce in many areas of the world. Finally, as word that sugar-based ethanol is more environmentally friendly spread and the biofuel industry jumped on the bandwagon, world sugar prices doubled, which is not good for a lot of world’s population.
All this means is that biofuels aren’t a biopanacea (yet) for replacing fossil fuels in our automobiles. As Fred Pearce points out, though, the industry is still in its infancy, and even the U.S. Department of Energy is funding research looking at alternative organic fuel sources that don’t have the downsides that corn and sugar do. The most promising alternative is fuel made from cellulose, the raw material that all plants are made of. One attractive possibility that’s been in the news lately is switchgrass. It can yield twice as much ethanol per acre as corn, and we can develop hybrids that grow on otherwise unused land with relatively low maintenance. What we need is an efficient process for converting the cellulose to ethanol. Stay tuned.
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