Biofuels might not be as clean as you thought, and they certainly aren’t carbon-neutral. The common thinking goes that crops used to make ethanol and biodiesel suck CO2 out of the air and turn it into a gas substitute. Then, when you fill up your car and take it for a spin, all you’re doing is releasing that carbon back into the atmosphere, not generating new emissions.
But for many years, environmentalists and academics have said that biofuels, depending on how they are cultivated and processed, could still lead to plenty of emissions and other environmental impacts. Now new research out of the University of Michigan shows how bad it is: In fact, biofuels might actually be worse, carbon-wise, than fossil fuels, it says.
"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," says lead author John DeCicco in a press release.
How much is "not enough"? According to DeCicco’s paper, crops only use 37% of the CO2 expended by the biofuel, although this was "during the period when U.S. biofuel production rapidly ramped up," which means production may not have been as efficient as it would be in a mature industry.
And biofuel is getting more popular. Usage in the U.S. has gone from from 4.2 billion gallons in 2005 to 14.6 billion gallons, partly based on government mandates. In 2013, biofuels accounted for nearly 6% of U.S. motor fuel energy consumption, says the paper.
A big part of the problem is that biofuel isn’t just about dropping a corn cob into your gas tank. The fuel needs to be processed, turning it either into biodiesel or ethanol, and both of these use energy, including energy from fossil fuels. Gallon for gallon, biofuel and gasoline both release the same amount of CO2 into the atmosphere, so the advantages of biofuels come down to the efficiency of its production.
"The United States uses 40% of its corn harvest to make ethanol," DeCicco told the Christian Science Monitor, "but that does not mean mean we eat 40 percent less corn-based products." To keep up with demand, forests are turned into cropland, but forests are better at removing CO2 from the air.
DeCicco’s study analyzes the carbon footprint of the entire biofuel production process, including crop production, and the production of fossil fuels used in making biofuels. And even while his 37% figure should improve, it still shows that biofuels are far from clean.
Not everybody agrees, though. Harvard geology professor Daniel Schrag, speaking to the Christian Science Monitor, points out that biofuels don’t have to be carbon-neutral. They just have to be better than fossil fuels. "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," said Schrag, "and those studies have gotten a range of answers, but it is about a 20% reduction of net emissions relative to gasoline."
The problem, then, seems to be less about the biofuel itself, and more about our obsession with cars. With a 20% reduction in emissions, biofuel seems like a pretty good way to power our cars, and it’s renewable too. But perhaps we should take the dwindling of gasoline as a sign to stop driving huge, heavy, fuel-hungry vehicles around on pointless journeys? We shouldn’t be trying to replace gasoline. We should be trying to replace cars.
Have something to say about this article? You can email us and let us know. If it's interesting and thoughtful, we may publish your response.