How green are biofuels? Scientists are at loggerheads

Enlarge / Abundantly growing corn plants in a corn field against a sunny blue sky. Nancybelle Gonzaga Villarroya/Getty

Tyler Lark, a geographer at the University of Wisconsin-Madison, grew up on farms, working in a neighbor's dairy, vaguely aware of the tension between clearing land to grow food and preserve nature. As an engineering student working on water projects in Haiti, he saw an extreme version of this conflict: forests cleared for firewood or to grow crops, resulting in soil erosion, denudation environment and the worsening of poverty. "I think it was that experience that told me, 'Hey, land use is important,'" he says.

He decided to study how farmers transform landscapes through their collective decisions to plow grasslands, clear trees, or drain wetlands; decisions that are at the heart of some of the biggest environmental challenges on the planet, and which also generate controversy. Lark bears professional scars after recently stumbling into one of the fiercest of these fights: the debate over the cultivation of crops used to make fuel for cars and trucks.

About 15 years ago, government incentives helped start a biofuel boom in the United States. Ethanol plants today consume about 130 million metric tons of corn each year. This is about a third of the country's total maize harvest, and growing this maize requires more than 100,000 square kilometers of land. Additionally, more than 4 million metric tons of soybean oil is turned into diesel fuel every year, and that number is growing rapidly.

Scientists have long warned that producing biofuels on this scale comes at a cost: it reclaims land that could otherwise produce food or, alternatively, grass and trees that sequester carbon from the air and provide shelter for birds and other wildlife. But government agencies, based on the results of economic models, concluded that these costs would be modest and that replacing gasoline with ethanol or biodiesel would help meet greenhouse gas reduction targets. greenhouse.

Lark and a group of colleagues have recently revived this debate. In a February 2022 study, they concluded that the law that sparked the ethanol boom persuaded farmers to plant corn on millions of acres of land that would otherwise have remained grassland. Environmentalists have long feared that biofuel production could lead to deforestation overseas; this article showed that a similar phenomenon was occurring in the United States.

This land conversion, the scientists concluded, would have released large amounts of carbon dioxide and other greenhouse gases into the air and made ethanol just as harmful to the climate as gasoline which it is supposed to replace.

Farmers and biofuel trade groups lashed out at these findings and at Lark himself. A biofuels industry association demanded that he and one of his co-authors be excluded from a government panel on renewable fuels.

The dispute has come at a time when world events have laid bare the trade-offs of biofuels. Less than two weeks after Lark's article appeared, Russia invaded Ukraine, causing the prices of food and fuel, which were already scarce and expensive due to the pandemic, to soar. Biofuel proponents have called for incentives to blend more ethanol into gasoline to drive down gasoline prices. Hunger advocates are demanding less biofuel production, to free up land to grow more food. And natural ecosystems continue to disappear.