Each converted hectare dumps about 351 metric tons of greenhouse gases on average into the atmosphere. Natural lands have been accumulating carbon for hundreds of years. It would take 167 years of ethanol production on that hectare to balance the equation, even assuming ethanol does reduce emissions 20 percent, according to Timothy Searchinger and colleagues in the other paper.
And Searchinger found this is the case for all biofuels, although the time frames differ. When a hectare of peatland rainforest in Indonesia or Malaysia is converted to grow oil palm trees for oil palm, it will take 423 years of producing palm biodiesel to work off the carbon debt from the conversion of these tropical forests.
Sadly, vast tracts of peatlands have already been cleared.
Last December, Susan Page, a leading expert on peatlands at the University of Leicester in England, reported that some 3.2 million hectares have been converted already and will put an astonishing 3.22 billion metric tons of greenhouse gases into the atmosphere over 25 years. Every metric ton of palm oil produced on this peatland will result in up to 70 metric tons of carbon dioxide over the life cycle of 25 years due to conversion, peat decomposition and emission from fires associated with land clearance, she found.
In 2005, 25 percent of all deforestation in Southeast Asia occurred on peatlands for palm oil plantations. The remaining forest peatlands are safely storing 50 billion to 70 billion metric tons of carbon.
"Current land use and land practice developments in Southeast Asia give grave cause for concern," Page said in a statement.
Surprisingly, these are the first studies to look at the impacts of global biofuel production on land clearing.
"These natural areas store a lot of carbon, so converting them to croplands results in metric tons of carbon emitted into the atmosphere," said Joe Fargione, a scientist for the Nature Conservancy and co-author of the Science paper.
Even Brazil's much touted sugarcane ethanol success story reveals that converting Cerrado grassland requires at least 17 years of sugarcane production to cover the carbon debt. Far worse is when Amazon forest is converted to grow soy for biodiesel -- in those cases the carbon debt will last 319 years.
And Brazilians are converting the Amazon forest at a record-breaking pace. In the last five months of 2007 alone, nearly 7,000 square kilometers have fallen, mainly in Mato Grosso, according to satellite observations. Biofuel is a major driver of this destruction. U.S. farmers are growing far more corn to feed the ethanol mills and much less soy than they used to. Meanwhile, the global demand for soy grows and Brazilian soy farmers clear the Amazon to grow even more.
"If you're trying to mitigate global warming, it simply does not make sense to convert land for biofuels production," Fargione said in a statement.
Conversion of conservation lands is happening in the U.S. as well. More than 12 million additional acres of corn were planted in 2007, and even more is expected this year. And all of those acres of corn-for-ethanol are making climate change worse. One quarter of the 2008 corn crop will become fuel.
That said, biofuels may have a future if they can be grown on degraded lands using perennial nonfood plants. Biofuels from waste biomass such as wood slash, straw and corn stalks using either cellulosic or gasification processes may also be biofuels that actually reduce emissions. However, using "wastes" deprive the soil of valuable organic matter, which is essential to soil productivity.
More study on the potential of these new technologies needs to be done, Tilman said.
And there is an essential need for an international set of standards for biofuel production so that governments and businesses will know which ones to invest in. Some biofuels offer a relatively cheap source of energy but have a very negative impact on the climate, he said. "We absolutely need a set of international standards."
The biofuel boom comes at a time when food production has to double to feed the 3 billion additional mouths expected by 2050. Now that many people in China and India and elsewhere can now afford to eat more meat, even more grain will be needed.
"In this context, it is a pretty silly idea to use food as fuel," Tilman said.
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Albion Monitor February
12, 2008 (http://www.albionmonitor.com)
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