A leading justification for mandating the sale of ever-greater amounts of ethanol and biodiesel in the nation's motor fuel supply is the claim that this will reduce greenhouse emissions and mitigate global warming. Horsefeathers! Three recent studies show that bio-fuel mandates actually contribute to global warming.
A study by Nobel laureate Paul Crutzon and colleagues estimates that nitrous oxide (N2O) emissions released by corn production cause up to 50 percent more global warming than the substitution of ethanol for gasoline avoids.
N2O is a potent greenhouse gas with 296 times the global warming potential of CO2. The researchers estimate that 3 to 5 percent of the nitrogen fertilizer used to grow corn (for ethanol in America) and rapeseed (for biodiesel in Europe) is converted to N2O. This contrasts with the IPCC's previously estimated conversion rate of about 2 percent.
The Crutzon study is not a “life-cycle” analysis, that is, it does not consider the CO2 released by the fossil fuels used to run the farm machinery, manufacture the fertilizer, operate the distilleries, or deliver the biofuel to market. Nor, on the other side of the equation, does it consider the CO2 avoided from commercial utilization of biofuel byproducts such as corn meal for animal feed. The researchers adopt an Olympian neutrality on this aspect of the subject, but I bet a life-cycle analysis would make corn ethanol look even sillier as global warming policy. Be that as it may, the study solely considers the balance between the N2O emissions released by the fertilizer used to grow bio-energy crops and the CO2 emissions avoided by substituting ethanol or biodiesel fuel for gasoline or petroleum diesel.
The bottom line: The N2O warming effect is 0.9-1.5 times the cooling effect of the avoided CO2 emissions in the case of corn ethanol and 1.0-1.7 times the cooling effect of the avoided CO2 emissions in the case of bio-diesel made from rapeseed.
"Leaping Before They Looked," a study by the Clean Air Task Force, reports that Europe's Biofuel Directive is increasing global CO2 emissions by encouraging firms and indigenous governments to clear and burn forests in peatlands in Indonesia, Malaysia, and other tropical countries to make room for palm oil plantations. Peatlands are rich stores of carbon, and when drained and dried -- and especially when burned -- they release enormous quantities of CO2 into the air. In fact, says the report, “recent peatland emissions more than swamp the CO2 reductions that Europe hoped to achieve under the Directive.” Some eye-popping specifics:
In 2006, Wetlands International and the Dutch consulting firm Delft Hydraulics reported that almost 12 million hectares of Indonesian peatland have been drained, cleared, and often burned—much of it to make room for oil palms. In the process, approximately 2000 million metric tons of CO2 are released annually, making peatlands destruction a leading source of global warming emissions. After accounting for these emissions — which equal 8% of global CO2 emissions from fossil fuel use — researchers determined that Indonesia's CO2 emissions were the third highest in the world, behind only the United States and China. (pp. 16-17)
Let's hear it for central planning and Soviet-style production quotas!
A study published in Science magazine looks at the biofuel/warming equation from a different angle. Whereas Crutzon et al. estimate the net warming impact of N2O emissions from fertilizer use, and the Clean Air Task Force examines the net CO2 increases from deforestation in tropical Asia, the study in Science examine which land use option -- growing bioenergy crops or saving and restoring forests -- has the bigger potential, per unit of land, to avoid CO2 emissions over the next 30 years.
The authors, Renton Righelato of World Land Trust and Dominick Spracklen of the University of Leeds, examine the potential of biofuels made from wheat, beets, cane, corn, and rapeseed to avoid CO2 emissions. They conclude:
In all cases, forestation of an equivalent area of land would sequester two to nine times more carbon over a 30-year period than the emissions avoided by the use of the biofuel. Taking this opportunity cost into account, the emissions cost of liquid biofuels exceeds that of fossil fuels.
Similar to the Clean Air Task Force, Righelato and Spracklen caution that producing significant quantities of biofuels will lead to deforestation, which also will increase net emissions:
A 10% substitution of petrol and diesel fuel is estimated to require 43% and 38% of current cropland area in the United States and Europe, respectively [ref. omitted]. As even this low substitution level cannot be met from existing arable land, forests and grasslands would need to be cleared to enable production of the energy crops. Clearance results in the rapid oxidation of carbon stores in the vegetation and soil, creating a large up-front emissions cost [ref. omitted] that would, in all cases examined here, outweigh the avoided emissions.