A new study from the University of Michigan has found that biofuels increase, rather than decrease, carbon dioxide emissions. The findings challenge the widely held assumption that ethanol, biodiesel and other biofuels are inherently carbon neutral.
The carbon dioxide gas emitted when biofuels are burned is not fully offset by the CO2 uptake that occurs as the plants grow, according to a study from the University of Michigan.
The study, which was based on crop-production data from the U.S. Department of Agriculture, found that increased carbon dioxide uptake by the crops only offset 37 per cent of the CO2 emissions caused by biofuel combustion. According to the researchers, rising biofuel use has in fact been associated with a net increase in carbon dioxide emissions.
“This is the first study to carefully examine the carbon on farmland when biofuels are grown, instead of just making assumptions about it, said professor John DeCicco said. “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.”
The U.S. Renewable Fuel Standard and other policies have strongly promoted the use of biofuels for transportation to displace petroleum use. The use of liquid biofuels – mainly corn ethanol and biodiesel – has more than tripled since 2005.
Lifecycle analyses and emissions modelling suggest that crop-based biofuel offer at least modest net greenhouse gas reductions relative to petroleum fuels. These are based on the assumption that the carbon dioxide released when biofuels are burned are derived in part from CO2 that the growing corn or soybean plants pulled from the atmosphere through photosynthesis, explains the University of Michigan.
But by analysing real-world data on crop production, biofuel production, fossil fuel production and vehicle emissions, the researchers found otherwise.
“When it comes to the emissions that cause global warming, it turns out that biofuels are worse than gasoline,” DeCicco said. “So the underpinnings of policies used to promote biofuels for reasons of climate have now been proven to be scientifically incorrect.”
Their findings were recently published in the journal Climatic Change.