Imagine—Fuel Alcohol From Pea Starch!

So you don’t like eating peas? Then how about fueling your car or truck with them? That’s a possibility Agricultural Research Service (ARS) scientists are exploring--using a type of fuel called ethanol, made from the legume’s starch.

Ethanol is among the cleaner-burning alternatives to petroleum, and is credited with reducing tailpipe emissions of carbon monoxide and other pollutants when added to gasoline.

In 2004, some farmers contacted ARS microbiologist Nancy Nichols about new ways to add value to their field pea crops. Most peas grown in the northern United States and elsewhere are fed whole to animals as a rich source of protein. The remainder is sold for human consumption as split peas. Besides protein, field peas also contain lots of starch. The farmers thought they might earn more if the crop’s starch could be used to make ethanol for fuel, while still using the leftover protein as high-value feed for animals.

To find out, Nichols teamed with Bruce Dien, a chemical engineer; Victor Wu, a chemist (formerly with ARS, now retired); and Mike Cotta, a microbiologist--all at ARS’ National Center for Agricultural Utilization Research, Peoria, Ill. There, they put whole peas through a three-step process.

First, they dry-milled the peas into flour. Next, they separated the protein and starch. Finally, they used enzymes and yeasts to ferment the starch’s sugars into ethanol.

During studies, the fermented pea starch produced somewhat less ethanol than corn (1.7 gallons per bushel versus 2.8), because the legume had less starch to begin with. But the pea starch fermented just as easily as corn starch. Potentially, the high yield of enriched protein, together with the fermentation leftovers, could be sold as livestock feed.

Economic modeling studies are now under way to determine whether using pea starch could be profitable to commercial ethanol plants, especially those located in areas where the legume is grown.

ARS is the U.S Department of Agriculture’s chief scientific research agency.