Biofuels are depicted as being bad for the environment -- and probably as bad as gasoline -- in a disconcerting new study from the University of Michigan Energy Institute (UMEI) that's being vigorously contested by other scientists.
The study published in journal of Climate Change claims more carbon dioxide is actually released when the crops from which corn ethanol and biodiesel biofuels are derived are being grown. It challenges the long-held hypothesis biofuels are more environmentally friendly because it's believed they emitted little to no carbon dioxide when being grown.
The study, however, also received funding from the American Petroleum Institute (API), the largest U.S trade association for the oil and natural gas industry. API describes its mission as to influence public policy in support of a strong, viable U.S. oil and natural gas industry.
Its chief functions on behalf of the industry include advocacy, negotiation and lobbying with governmental, legal and regulatory agencies.
The UMEI study suggests biofuels can mitigate only 37 percent of the CO2 released by burning biofuels. Biofuels, which are usually derived from corn or soybeans, accounted for six percent of all fuel sources in the U.S. in 2013. The use of biofuels and other products such as ethanol has tripled from 4.2 billion gallons in 2005 to 14.6 billion gallons in 2013.
A UMEI research team led by Dr. John DeCicco analyzed the amount of CO2 absorbed as crops grow and then released when they're burned as biofuel. They calculated the total U.S. crop yield can remove only 37 percent of the CO2 that burning biofuel releases into the air.
"What we found is that when you actually look at how quickly crops like corn and soybeans pull CO2 from the air and compare that with the emissions that occur when the biofuels like ethanol and biodiesel are burned, you find out that they are not carbon neutral like everyone has been assuming," said Dr. DeCicco.
Dr. DeCicco said that to verify the extent to which the assumption biofuels are carbon neutral is true, you really need to analyze what's going on in the farmland where the biofuels are being grown.
"People haven't done that in the past -- they felt like they didn't need to."
The UMEI study includes tailpipe emissions and crop growth that are instrumental in growing crops used for biofuels. It found carbon emissions during that period actually only absorbed 37 percent of biofuel production from 2005 to 2013.
This finding directly contradicts previous studies claiming biofuels use emitted less carbon than using gasoline.
"When you look at what's actually happening on the land, you find that not enough carbon is being removed from the atmosphere to balance what's coming out of the tailpipe," said Dr. DeCicco. "(Biofuels) is unambiguously worse than petroleum gasoline."
Prof. Daniel Schrag, a geology professor at Harvard who advises the EPA on bioenergy climate impacts, said Dr. DeCicco is working on a flawed premise. He said biofuels don't have to be carbon neutral to be an environmentally preferable alternative to petroleum gasoline.
"For about 10 years there have been very careful studies of corn ethanol and all of the fossil carbon that is used to make it ... and those studies have gotten a range of answers, but it is about a 20 percent reduction of net emissions relative to gasoline," said Schrag.
"Nobody ever thought corn ethanol was carbon neutral, because there are lots and lots of fossil inputs to it."
Dr. Michael Wang, a researcher at the Argonne National Laboratory, also questions the UMEI study's carbon accounting. He noted the study doesn't properly account for carbon uptake or that corn production for both ethanol and for food increased over the period of the study.
"The carbon uptake by the US farming systems is calculated based only on grain harvest," said Dr. Wang. "Carbon uptake embedded in above- and below-ground biomass is ignored in the paper with a simple assumption that carbon in these biomass sources are oxidized back to the air."