In Brazil, BP owns two ethanol producers—Companhia Nacional de Açúcar e Álcool andTropical BioEnergia—with three ethanol mills.[229] These mills produce around 800,000 cubic metres per annum (5,000,000 bbl/a) of ethanol equivalent.[254] BP has invested in an agricultural biotechnology company Chromatin, a company developing crops that can grow on marginal land and that are optimized to be used as feedstock for biofuel.[255] Its joint venture with DuPont called Butamax, which has developed the patented bio-butanol-producing technology,[256] and owns an isobutanol plant in Scandia, Kansas, United States.[5] In addition BP owns biomethane production facilities in Canton, Michigan, and North Shelby, Tennessee, as well as share of facilities under construction in Oklahoma City and Atlanta.[6] BP's subsidiary Air BP supplies aviation biofuel at Oslo, Halmstad, and Bergen airports.[257]