A longtime critic of U.S. biofuels says an expansion of biofuels policy under President Donald Trump would lead to more greenhouse gas emissions and fewer food crops.By Georgina GustinThe American Midwest is home to some of the richest, most productive farmland in the world, enabling its transformation into a vast corn- and soy-producing machine—a conversion spurred largely by decades-long policies that support the production of biofuels.