API-funded study takes aim at biofuels’ carbon neutrality

Source: Niina Heikkinen, E&E reporter • Posted: Friday, August 26, 2016

New research funded in part by the American Petroleum Institute finds that burning ethanol and biodiesel for fuel is not carbon-neutral.

The findings contradict the widely accepted assumption that carbon released by burning biofuels will be replaced through the growth of feedstock crops like corn, said John DeCicco, a research professor at the University of Michigan Energy Institute who led the study.

The concept that the burning of biofuels is carbon-neutral underlies much of the current modeling of the environmental impact of ethanol done by the Department of Energy and U.S. EPA, and has been used by the California Air Resources Board, he said. DeCicco’s research has aimed to steadily pick apart this model and reframe how scientists calculate biofuel emissions.

“The carbon neutrality assumption has been used for years, it seems logical, but it’s just an assumption,” he said.

DeCicco and his colleagues tested whether ethanol and biodiesel were carbon-neutral by comparing how much carbon was released through burning biofuels and ethanol fermentation to the crop yields on U.S. farmland between 2005 and 2013.

The researchers used Department of Agriculture data on crop area, harvested area, crop yield and production to calculate the amount of total crops produced. They also used EPA data from 2010 on the carbon content for combustion of biofuels.

Over the eight-year period, they found that cumulative emissions from burning biofuels and fermenting ethanol reached 132 million metric tons of carbon, while the cumulative increase in carbon uptake since 2005 equaled 49 million metric tons. The crops were only able to offset 37 percent of the cumulative emissions.

Their research was published today in the journal Climatic Change.

Critics find ‘fundamental flaws’ in research

The study’s findings build on DeCicco’s previous research, which has challenged the life-cycle analysis model that is used to determine the carbon neutrality of burning biofuels and replaces it with his own ABC model — annual basis carbon accounting. DeCicco frequently testifies before Congress about biofuel emissions and has critiqued the efficacy of the renewable fuel standard.

In addition to arguing that biofuels are not carbon-neutral, DeCicco says they are actually worse carbon emitters than gasoline because the carbon released through direct and indirect land-use change from growing feedstocks is greater than the amount of carbon released through petroleum extraction.

“When you replace actual lands that are rich in carbon stocks, directly or indirectly, you in a short period of time release a huge amount of carbon into the atmosphere that creates a carbon debt,” he said.

Michael Wang, senior scientist at DOE’s Argonne National Laboratory, called the study’s 37 percent finding “highly questionable.”

One problem, he said, was the data used to calculate the carbon content of crops focused only on the grain yields but did not consider the carbon stored in the rest of the plant.

Wang also pointed to a line in the paper’s discussion, which noted the results from the ABC analysis were “for a specific period of time and so makes no claim to offer a general characterization of corn ethanol.”

“While the ABC approach may sound reasonable in theory, in practice it suffers from some fundamental flaws,” Wang said.

Richard Plevin, a research scientist at the University of California, Berkeley’s Transportation Sustainability Research Center, said that generally speaking, defining the carbon neutrality of biofuels was complicated and that experts disagree about how to go about getting answers.

What scientists should be trying to figure out is if producing more biofuel will mitigate climate change, which isn’t answered by studying whether life-cycle greenhouse gas emissions for biofuels are more or less than fossil fuels, he said.

“In most cases, we really don’t know if producing biofuels mitigates or exacerbates climate change,” Plevin wrote in an email.