Ethanol likely worse than gasoline for carbon emissions, say researchers
The Renewable Fuel Standard, which guarantees corn ethanol and other biofuels a share of the U.S. gasoline market, results in the release of at least as much carbon “and likely at least 24% higher” greenhouse gas emissions than the petroleum it displaced, say scientists who studied the program’s first eight years.
“Our findings suggest that profound advances in technology and policy are still needed to achieve the intended environmental benefits of biofuel production and use,” they wrote in the journal Proceedings of the National Academy of Sciences on Monday.
Although conventional biofuels such as corn ethanol were projected to generate life-cycle reductions in emissions of at least 20%, “we find that the production of corn-based ethanol in the United States has failed to meet the policy’s own greenhouse gas emissions targets and negatively affected water quality, the area of land used for conservation, and other ecosystem processes,” without considering possible effects on cropping patterns overseas, they said.
Farmers put more land into corn production—with resultant increases in fertilizer use, nutrient runoff and soil erosion—and converted more grasslands to crop production, said the researchers.
An average 1.3 billion bushels a year of corn was used by ethanol makers because of the RFS, according to the researchers. “This heightened demand led to persistent increases in corn prices of around 31%,” they said. Higher corn prices pulled up the market price of soybeans, wheat and other alternative crops.
“Substituting our empirically derived domestic emissions for those modeled in the RFS [regulatory impact analysis] would raise ethanol’s projected life cycle GHG emissions for 2022…a value 24% above baseline gasoline,” they concluded.
Biofuels are often proposed as a way to reduce greenhouse gas emissions and limit the scope of climate change.
“As policy-makers worldwide deliberate the future of biofuels, it is essential that they consider the full scope of the associated tradeoffs, weighing the GHG and other environmental externalities alongside each fuel’s benefits,” said the group of nine scientists.
The PNAS study, “Environmental outcomes of the US Renewable Fuel Standard,” is available here.