Andre Bernard made a killing selling a mirage.

As oil refineries struggled to comply with federal mandates for blending renewable fuels into the nation’s gasoline and diesel supply, Bernard offered a solution: millions of dollars’ worth of biofuel credits they could buy to help meet their obligation. The credits were ostensibly generated by biofuel companies Bernard and his partners owned.

The only problem is they weren’t making the fuel. They were faking it, generating at least $42 million worth of phony credits. Bernard was sent to prison last month.