Corn ethanol and other first-generation biofuels are a clean, climate-friendly alternative to fossil fuels.

The logic of biofuels seemed straightforward in 2007. Plants absorb carbon dioxide as they grow; burn the fuel refined from those plants, and you release that same carbon back, a closed cycle, unlike burning ancient fossil fuels that release carbon sequestered for millions of years. Corn ethanol, blended into gasoline at filling stations across the Midwest, was presented in environmental education as a practical step toward reducing transportation emissions. The Energy Independence and Security Act, signed into law in December 2007, mandated 36 billion gallons of renewable fuel by 2022, with corn ethanol forming the foundation of the target.

The life-cycle analysis told a different story. In February 2008, two papers published in Science, one by Timothy Searchinger and colleagues, another by Joseph Fargione and colleagues, examined what happened when the full chain was included. Growing corn for ethanol required land. That land had previously been in other uses: forests, grasslands, cropland growing food. Converting land to energy crops released enormous stores of carbon held in soil and vegetation. When these land-use-change emissions were included in the calculation, corn ethanol was not carbon-neutral, in Searchinger’s analysis, it would take more than 160 years of biofuel use to repay the carbon debt from land conversion.

The food consequences were equally unwelcome. The corn ethanol mandate diverted a substantial fraction of US corn production from food to fuel. Global food prices, already rising due to population growth and drought in key producing regions, spiked sharply in 2007 and 2008. The UN Food and Agriculture Organization identified biofuel expansion as a contributing factor in the food crisis that sparked civil unrest across more than thirty countries. The clean-energy alternative had helped price staple grains out of reach for the world’s poorest consumers.

Second-generation biofuels, made from agricultural waste, dedicated energy grasses grown on marginal land, or algae, could avoid the worst of these problems in principle. But they remained largely unscalable through the late 2000s. Cellulosic ethanol, which featured prominently in the 2007 energy act’s mandate, never reached projected volumes; the technical and economic barriers proved more stubborn than advocates had hoped. The biofuel episode was not evidence that renewable energy was impossible, but that a solution ignoring indirect effects, land use, food systems, global supply chains, can cause as much harm as the problem it addresses.