The U.S. Court of Appeals for the Federal Circuit has undone a win for renewable energy firm Gevo and its lawyers at Cooley in a patent showdown with Butamax, a biofuels joint venture formed by BP and DuPont.

U.S. District Judge Sue Robinson of Delaware had granted Gevo’s motions for summary judgment for noninfringement and invalidity for lack of a written description against Butamax in March 2013. Robinson also denied Butamax’s bid for a finding of infringement.