Some biofuels might do more harm than good to the environment, s...(t definitive at all Groom said but rat...)

These concerns are becoming more acute with the rapid rise of both food and fuel prices, she said. The issue is especially touchy for farmers who might for the first time be realizing significant profits on their crops, but it also is a serious concern for motorists.

"I've heard about people getting their gas tanks siphoned, and I hadn't heard of that since the '70s," she said.

A difficulty, Groom said, is that while escalating prices add pressure to find less costly fuel sources, acting too hastily could create a host of other problems. For example, farmers who plant only corn because it is suddenly profitable, and don't rotate with crops such as soybeans, are likely to greatly deplete their soil, which could limit crop growth and promote soil erosion.

Also, some plants are better than others for absorbing carbon dioxide from the atmosphere, while others perhaps need more cultivation, which requires more fossil fuel for farm equipment. In addition, fertilization, watering and harvesting all require energy.

The study took about a year to conduct and is a synthesis of peer-reviewed research published in a various journals. The scientists examined the literature looking for indicators of biofuels that are more sustainable and carry a smaller ecological footprint, then used that information to derive the policy recommendations.

The primary audiences for the work are policy makers, students and other biologists, Groom said. The primary goals are to establish a logical basis to evaluate options for biofuel development and to spur new research to find the most ecologically promising alternatives.

"We don't want to make new mistakes. If we don't ask the right questions to start with, we're going to replace old problems with new ones," she said.

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