Biofuels have for years divided energy experts and environmentalists. Critics say that they displace farmland and cause deforestation. Proponents argue they are a green, low-carbon alternative to petroleum-based fuels.

A new analysis adds fuel to the incendiary topic. Researchers report in the journal Climatic Change that biofuels might harm the climate more than petroleum. Substituting petroleum fuels with biofuels in American vehicles has led to an increase in net carbon dioxide emissions over the eight years covered by their study, they calculate.

The U.S. Environmental Protection Agency’s Renewable Fuel Standard has set an annual production target of 36 billion gallons of biofuel in 2022. The push for biofuels is based on life-cycle analyses, which assume that fuel crops absorb carbon dioxide as they grow, and this carbon negation effect adds up over time.

For the new study, researchers at the University of Michigan Energy Institute analyzed real-world data from 2005–2013 on crop production, biofuel production, gasoline production, and vehicle emissions. They analyzed how much carbon dioxide corn and soy plants pull from the air while growing, and how much of it they release when burned.

The result? Growing fuel crops only absorb 37 percent of the carbon dioxide that burning biofuel releases. “This shows that biofuel use fell well short of being carbon neutral even before considering process emissions,” said lead researcher John DeCicco.

The research, funded by the American Petroleum Institute, has garnered both criticism and praise. Praise came from researchers who say traditional life-cycle calculations of biofuels’ climate impact have been flawed, and that biofuels don’t need national growth targets and subsidies. Critics, meanwhile, pointed out that the study does not take into account the long timescale it takes for crops to soak up carbon emissions.

Plus, as a news story in Wired pointed out, the researchers only looked at corn ethanol and soy biodiesel. Fuels made from cellulosic sources such as grasses, stems, and leaves are widely accepted to be less carbon intensive in addition to not competing with farmland. —Prachi Patel | 8 September 2016

Source: John M. DeCicco et al. Carbon balance effects of U.S. biofuel production and use. Climatic Change. 2016.

Photo: Wikimedia Commons