Most players in the transportation debate, including politicians, industry representatives, environmentalists, and researchers, agree that fuels from plant waste offer promise. However, it takes chemistry to turn solid biomass into liquid fuels.
Researchers seeking to make ethanol must first unlock sugars from the plant polymer called cellulose and other plant carbohydrates. “Cellulose looks like a long string of pearls,” explains Charles Wyman of Dartmouth College in Hanover, N.H. “The individual pearls are the sugar-monomer units.” Yeast and bacterial cells can ferment those individual sugar monomers into alcohol.
Unlike starch from corn grains, cellulose is difficult to break up into its constituent sugars. The recalcitrance of cellulose poses the biggest challenge facing biomass-to-fuel technology. “Cellulose is in plants to give the plants rigidity,” says Joel Cherry of Novozymes in Davis, Calif. “Starch is in plants to feed seeds when they grow. It’s made by nature to be broken down.”
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