In 2007, at the urging of President George W. Bush, Democrats and Republicans together created a massive new mandate for the production and sale of biofuels. It was environmental folly.

The public is familiar with that part of the renewable fuel mandate about ethanol, the politically favored, wasteful, and environmentally destructive product that is blended into gasoline thanks to federal law. But the biodiesel side of this business is less well-known.