The company announced its departure from the solar energy market in December 2011 by closing its solar power business, BP Solar.[114] In 2012, BP shut down the BP Biofuels Highlands project which was developed since 2008 to make cellulosic ethanol from emerging energy crops like switchgrass and from biomass.[115][116] In 2015, BP decided to exit from other lignocellulosic ethanol businesses.[117] It sold its stake in Vivergo to Associated British Foods.[118] BP and DuPont also mothballed their joint biobutanol pilot plant in Saltend.[119]