The rush to grow biofuel crops – widely embraced as part of the solution to global warming – is actually increasing greenhouse gas emissions rather than reducing them, according to two studies published Thursday in the journal Science.
One analysis found that clearing forests and grasslands to grow the crops releases vast amounts of carbon into the air – far more than the carbon spared from the atmosphere by burning biofuels instead of gasoline.
“We’re rushing into biofuels, and we need to be very careful,” said Jason Hill, an economist and ecologist at the University of Minnesota who co-authored the study. “It’s a little frightening to think that something this well intentioned might be very damaging.”
Even converting existing farmland from food to biofuel crops increases greenhouse gas emissions as food production is shifted to other parts of the world, resulting in the destruction of more forests and grasslands to make way for farmland, the second study found.
The analysis calculated that a U.S. cornfield devoted to producing ethanol would have to be farmed for 167 years before it would begin to achieve a net reduction in emissions.
“Any biofuel that uses productive land is going to create more greenhouse gas emissions than it saves,” said Timothy Searchinger, a researcher at the Woodrow Wilson School of Public and International Affairs at Princeton University and the study’s lead author.
Since 2000, annual U.S. production of corn-based ethanol has jumped from 1.6 billion gallons to 6.5 billion gallons – supplying about 5 percent of the nation’s fuel for transportation, according to the Renewable Fuels Association.
Federal legislation passed last year calls for production of ethanol to more than double over the next decade.
Food crops such as corn, palm oil, sugar cane and soy beans have so far been the main source of biofuels because they are already grown in abundance and relatively easy to convert.
The fuels are environmentally attractive because, unlike fossil fuels, they are theoretically carbon-neutral. Carbon is released when the fuel is burned, but a similar amount is absorbed from the atmosphere as the crops grow.
Calculating the actual increase or decrease in carbon emissions has been difficult because of myriad factors involved, such as the energy used to produce the fuels and the varying amounts of carbon released through cultivation.
The biggest source of emission, by far, comes from land-use changes associated with biofuels, the new studies showed.
Several scientists said it is becoming clear that the biofuel industry needs to focus on potential biofuel sources that do not increase pressure on land, such as municipal trash, crop waste and prairie grasses.
The government is also promoting those sources, but there are still technological hurdles, and the powerful agricultural lobby has put its weight behind food-based biofuels to boost crop prices for farmers.
“We need better biofuels before more biofuels,” said Alex Farrell, a professor of energy and resources at the University of California at Berkeley who was not involved in the study.