A combine harvester during a soybean harvest in Illinois, October 2025. | Bloomberg via Getty ImagesThe modern soybean is one of the world’s miracle technologies, capable of cheaply, efficiently, and healthfully supplying protein and other nutrients to billions of people. But, unfortunately, we’ve mostly chosen to squander it on the most destructive purposes possible. Soy is America’s second most widely cultivated crop, occupying a land area equivalent to more than 4 percent of the continental US. That’s not (sadly) because we’ve become a nation of tofu obsessives. Rather, American soy production has expanded substantially in recent decades in part because the US government effectively mandates funneling it into fuel tanks. (The other major market for American soy, meanwhile, is feed for factory farmed animals.)For the past 20 years, the US Renewable Fuel Standard (RFS) has required that biofuels — fuels made from crops and other biological materials like animal waste — be mixed into the national fuel supply. In practice, it’s dominated by corn ethanol that goes into passenger car tanks, and biomass-based diesel, comprised in large part of soybean oil, used to power trucks, tractors, and buses. And last month, the Environmental Protection Agency’s 2026-2027 rules for the Renewable Fuel Standard took effect, turbocharging that system with an unprecedented, nearly 70 percent increase in the biomass-based diesel mandate, relative to the 2025 baseline.Ostensibly, part of the point of the Renewable Fuel Standard is to reduce greenhouse gas emissions by replacing some of our fossil fuels with renewable, less carbon-intensive ones. So it might come as a surprise that the Trump administration, which has been gleefully canceling anything having to do with green energy and climate policy, is expanding the program. But the RFS as currently designed does not benefit the climate — it actually probably harms it. Few experts outside the powerful agrarian lobby defend the Renewable Fuel Standard in its current, crop-heavy form as sound policy anymore. It survives now mostly to guarantee a market to corn and soy growers. These are industries that President Donald Trump is particularly keen to please after angering farmers with his trade war last year and the disruptions to global trade — including fertilizer supplies — from the war in Iran. The soy industry has hailed the program’s latest, massive increase in the biomass-based diesel quota. But it will likely come at the cost of more ecological damage than the fuels it’s meant to replace. Many biofuels are likely worse than fossil fuelsThe first wave of interest in modern biofuels came during the 1970s energy crisis, as the US sought to reduce its dependence on foreign oil. But it wasn’t until the mid-2000s, when the RFS was devised, that they became a routine part of nearly every American’s trip to the gas pump. At the time, the thinking was that biofuels were less damaging to the climate than petroleum fuel, because at least growing corn and soybeans draws some carbon out of the air via photosynthesis, while extracting and burning oil only releases it. But that reasoning has been mostly discredited by a large body of research finding that biofuels made with food crops are just as bad, and perhaps even worse, for the climate than conventional fossil fuels. The main reason for this is land-use change, a concept that is more exciting than it sounds because it refers in this case to the destruction of our planet’s remaining wildlands. When the government suddenly mandates that billions of gallons of biofuel be added to gas pumps nationwide, the crops for that fuel must, to state the obvious, be grown somewhere. One widely cited study of the environmental impacts of the Renewable Fuel Standard found that between 2008 and 2016, the program caused the conversion of about 4.45 million acres of natural and seminatural areas into cropland in the US. And any time wild areas are cleared for agriculture, a substantial amount of greenhouse gases are emitted from the razing of existing vegetation and disturbance of carbon-rich soils. Whatever carbon sequestration results from growing crops does not make up for these impacts, nor for the lost carbon storing capacity of the preexisting ecosystem. As a result, the study found, for example, “the carbon intensity of corn ethanol produced under the RFS is no less than gasoline and likely at least 24 percent higher.”Meanwhile, although the soy and corn used in US biofuels are overwhelmingly American-grown, the Renewable Fuel Standard’s impacts don’t stop at our borders. Crop-based diesel mandates in particular, driven by the RFS and similar policies in other countries, have created a huge new source of demand for vegetable oils on top of what’s already needed for food. As of 2023, about 17 percent of global vegetable oil is diverted to diesel production. That has had devastating impacts on wildlands abroad, especially the world’s remaining tropical forests.It works like this: When US policy requires that massive amounts of crop-based diesel be added to our fuel supply, the market price of soybean oil rises around the world. The prices of other widely used vegetable oils — sunflower, canola, and palm — rise in tandem, because food manufacturers use them interchangeably with soybean oil in a massive range of packaged products, like salad dressings, Oreos, crackers, and others.Higher prices signal to farmers around the globe to grow more vegetable oil crops. That can mean more soybean acreage in the South American Amazon, more canola or sunflower fields elsewhere, and more oil-palm plantations in Southeast Asia, where agricultural expansion into tropical forests and peatlands is especially destructive. The upshot is that using crops for fuel expands the world’s total cropland, pushing agriculture into forests, grasslands, and other wild areas — a mechanism known as indirect land-use change. The more American soybean oil goes into fuel tanks, the more food companies can and will simply replace it with palm oil. A recent working paper by a group of University of California agricultural economists detailed how global demand for biomass-based diesel has accelerated deforestation in Southeast Asia. Between 2002 and 2018, they found, about 4.2 million acres of forestland in Indonesia and Malaysia were converted to palm oil plantations as a result of global vegetable-oil-based diesel demand — about 20 percent of all forest-to-oil-palm conversion in the region during that period. Accounting for these deforestation impacts, the authors found, makes vegetable-oil-based diesel about 22 to 52 percent higher in greenhouse gas emissions than petroleum diesel — and that does not include the impacts of land-use changes caused by biodiesel anywhere else in the world. Agricultural economist Richard Sexton, one of the authors of that study, told me in an interview last year: “We are deforesting Indonesia and Malaysia due to our biofuel policies.” And, of course, these forests are much more than carbon reservoirs. They are also the home of critically endangered orangutans and countless other species that live nowhere else on Earth. All of this will be made worse by the new RFS mandates, which are projected to drive by far the largest increase in soy-based diesel use in the program’s history.There is another important consequence of biofuels mandates. By diverting valuable crops into the fuel supply, they have put upward pressure on global food prices, especially squeezing the world’s poor, who spend a very large share of their household incomes on food. There’s a bigger lesson here. Support for biofuels mandates in the US, like support for policies that favor farmers more generally, is a bipartisan affair, shielded by “a force field of agro-political influence,” as journalist Michael Grunwald phrased it in his book We Are Eating the Earth. Surely part of the reason that it’s been possible for the Renewable Fuel Standard to skate by for so long is that, unlike fossil fuels, farming seems natural and virtuous. But all farms, as Grunwald puts it, are “a kind of environmental crime scene,” responsible for the devastation of the ecosystems that came before them. Biofuels mandates may now be too politically entrenched to disappear anytime soon. But it is possible, at a minimum, to limit further acceleration. The corn ethanol mandate has remained roughly flat for over a decade, and the EPA could certainly change its rules to prevent the continued proliferation of soy-based diesel. In the long term, the transition toward electric vehicles may finally render crop-based biofuels obsolete (for road transportation, at least — aviation is a different story). But in the meantime, the least we can do is to stop expanding them.