A comprehensive analysis of the full life cycles of two biofuels, the biodiesel and the ethanol, has showed that corn grain ethanol is much less beneficial than soybean biodiesel, U.S. scientists reported on Monday.

However, neither fuel has the potential to replace petroleum as a primary fuel of a society, a research team at the University of Minnesota noted in the July 10 edition of the Proceedings of the National Academy of Sciences.

The researchers studied the costs and benefits associated with using American croplands for biofuel production, finding both corn grain ethanol and soybean biodiesel produce more energy than is needed to grow the crops and convert them into biofuels.

The finding refutes other studies claiming the biofuels require more energy to produce than they provide.

But the amount of energy each returns differs greatly. The researchers found ethanol from corn produces 25 percent more energy than was invested in it, while biodiesel from soybeans produces 93 percent more.

Biodiesel also has significantly less environmental impact in terms of nitrogen, phosphorus and pesticide pollution, the researchers said. Compared with fossil fuels, ethanol produces 12 percent fewer greenhouse gas emissions, while biodiesel produces 41 percent less.

Soybean biodiesel is superior to ethanol in another way: it requires less agricultural inputs and is more efficiently converted into fuel, according to the researchers.

Also, biofuels produced on low-productive agricultural land or from waste may provide even larger fuel supplies with greater environmental benefits.

Still, the researchers cautioned that neither biofuel can come close to meeting the growing demand for alternatives to petroleum.

All current U.S. corn and soybean production can convert into only 12 percent of gasoline demand and 6 percent of diesel demand, while global population growth and increasingly affluent societies will increase demand for corn and soybeans for food, the researchers noted.

"Corn ethanol and soybean biodiesel are successful first generation biofuels," said David Tilman, a professor that co-authored the study.

"The next step is a biofuel crop that requires low chemical and energy inputs and can give us much greater energy and environmental returns. Prairie grasses have great potential."

Biofuels such as switchgrass, mixed prairie grasses and woody plants harvested on marginally productive agricultural land, or biofuels produced from agricultural or forestry waste, will have the potential to provide much larger energy supplies with greater environmental benefits than first generation fuels, the researchers suggested.

Source: Xinhua