Biofuels based on ethanol, vegetable oil and other renewable sources may be popular as a way to reduce fossil fuel dependence and limit greenhouse gas emissions but now a new study shows that some of the most popular current biofuel stocks might have exactly the opposite impacts than intended.
The study, led by a biologist at the University of Washington, offer a dozen policy recommendations to promote sustainability and biodiversity in biofuel production.
For the study, researchers examined factors such as the energy needed to produce a renewable fuel source compared with how much energy is produced, the impact on soil fertility and effects on food supply when fuels based on crops such as corn and soybeans are mixed with fossil fuels.
Based on those factors, the researchers determined that corn-based ethanol is the worst alternative overall.
"It's foolish to say we should be developing a particular biofuel when that could mean that we're just replacing one problem with another," said lead author Martha Groom of the UW Bothell.
The researchers called for precise calculations to determine the ecological footprints of large-scale cultivation of various crops used for biofuels.
For example, they noted that because such large amounts of energy are required to grow corn and convert it to ethanol, the net energy gain of the resulting fuel is modest.
Using a crop such as switchgrass, common forage for cattle, would require much less energy to produce the fuel, and using algae would require even less.
Changing direction to biofuels based on switchgrass or algae would require significant policy changes, since the technologies to produce such fuels are not fully developed.
Groom said however said that the study's policy suggestions are 'not definitive at all but rather each category calls out a question and is a starting point in trying to find the proper answers.'
She said that these concerns are becoming more acute with the rapid rise of both food and fuel prices.
Groom said a difficulty 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.
Besides this, 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 researchers 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.
Groom said that the primary audiences for the work are policy makers, students and other biologists.
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.
The study is published in the June issue of the journal Conservation Biology.