Producing biofuels using food crops will release more global warming carbon dioxide into the atmosphere than producing and burning good old-fashioned gasoline, say new studies published today in Science.
New Scientist sums the research up this way:
The new studies examine a different part of biofuel equation, and both suggest that the emissions associated with the crops may be even worse than that.
One analysis looks at land that is switched to biofuel crop production. Carbon will be released when forests are felled or bush cleared, and longer-term emissions created by dead roots decaying.
This creates what Joseph Fargione of The Nature Conservancy and colleagues call a "carbon debt". Emissions savings generated by the biofuels will help pay back this debt, but in some cases this can take centuries, suggests their analysis.
If 10,000 square metres of Brazilian rainforest is cleared to make way for soya beans – which are used to make biodiesel – over 700,000 kilograms of carbon dioxide is released.
The saving generated by the resulting biodiesel will not cancel that out for around 300 years, says Fargione. In the case of peat land rainforest in Indonesia, which is being cleared to grow palm oil, the debt will take over 400 years to repay, he says.
The carbon debts associated with US corn are measured in tens rather than hundreds of years. But the second study suggests that producing corn for fuel rather than food could have dramatic knock-on effects elsewhere.
Corn is used to feed cattle and demand for meat is high, so switching land to biofuel production is likely to prompt farmers in Brazil and elsewhere to clear forests and other lands to create new cropland to grow the missing corn.
When the carbon released by those clearances is taken into account, corn ethanol produces nearly twice as much carbon as petrol.
"The implications of these changes in land use have not been appreciated up until now," says Alex Farrell, at the University of California, Berkeley, US.
Farrell adds that biofuels could still prove useful in the fight against climate change, but using different approaches – such as focusing on crops for both food and fuel, or new technology for generating biofuels from food waste.
Of course, the studies may not pan out, but still the fact that Congress just mandated the production of 36 billion gallons of bio-ethanol for transport fuel by 2022 might give one pause to consider the virtues of letting government officials select our future energy technologies. Yes, I know, I know, the legislation mandates that about half of it must come from cellulosic sources, not food, but nobody knows how to do that yet economically.
Did someone say something about carbon taxes?