Can you explain the climate impact of biofuels?

Tim Searchinger is a research scholar at the Center for Policy Research on Energy and the Environment at the Woodrow Wilson School at Princeton University. He has been a longtime critic of biofuels and biofuels policy, publishing research more than a decade ago that challenged the idea of biofuels as a carbon neutral energy source.

Searchinger said most analyses that show a carbon benefit from biofuels don’t calculate the opportunity cost. 

“The basic way to think about it is: Biofuels are a way of using land to produce a plant to benefit the climate by replacing fossil fuels, but the cost is not using that land for some other purpose,” Searchinger explained. “Almost all the calculations that show benefits treat the land as free. They look at the benefits but not the cost.”

“We produce corn to eat, and if you’re not producing it in one place you have to produce it somewhere else,” Searchinger added.

Searchinger said that as biomass is diverted to biofuels, it triggers the clearing of forests or other lands to grow more corn, which are better at storing carbon than agricultural lands. This “indirect land-use change” effectively cancels out the greenhouse benefits of biofuels. 

Searchinger and his research colleagues said that studies showing a climate benefit fail to adequately account for the total carbon emitted through the biofuels life cycle. Much of that stems from an accounting mistake, in which the carbon emissions are counted only when biomass is harvested or cut, and not when it’s burned. 

“The usual explanation is that this carbon dioxide is automatically offset, that is, canceled out, by the carbon dioxide absorbed by plants when they grow,” Searchinger wrote in a sweeping 2019 report. “Because of this plant growth offset, the theory is that bioenergy does not add more carbon to the atmosphere, whereas burning fossil fuels adds new carbon to the air that would otherwise stay underground. Based on this theory, nearly all analyses estimating the climate benefits of bioenergy do not count the carbon dioxide released when biomass is burned.”

He also said that there’s no additional carbon absorption from growing corn on land where it’s already being grown. “That carbon absorption was going to happen anyway,” he explained. “Diverting it to ethanol doesn’t absorb more carbon.”

He added, “You can come up with extreme cases, with extreme assumptions, where you can claim a net gain, but then it’s a small percentage. Even then, the amount of carbon savings, per acre of land, of using biofuels is very small.” 

Georgina Gustin

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