Which biofuels reduce greenhouse emissions

Researchers from the U.S. Department of Agriculture and Colorado State University think they've found a better way to power your car. They used computer models to figure out which biofuel sources are best at reducing greenhouse gas emissions. That would help, they say, reduce global warming.

First, they found that nitrous oxide is the major greenhouse emission from biofuels. The savings comes from displaced fossil fuels. They looked at six biofuel crops likely to succeed in the U.S. All were found to reduce greenhouse gases when compared with gasoline or diesel.

Corn and soybean rotations were 40 percent better than fossil. Reed canarygrass was 85 percent better. Switchgrass and hybrid poplar (trees, that's right!) were 115 percent better. They found no gain in using alfalfa.

Bring back the buffalo! Switchgrass covered the American plains for hundreds of miles when the buffalo roamed free. It's a native prairie grass. Hybrid poplars could be grown in tree farms in a variety of climates.

This research appears in a journal just published by the Ecological Society of America. One surprising find: switchgrass and poplar become even better energy sources if they're used to produce electricity via biomass gasification. Then they're twice as effective as fossil fuels.