Oxidation of sugarcane bagasse using a combination of hypochlorite and peroxide

Abstract

Sugarcane bagasse is a source of lignocellulosic biomass. It is a potential renewable energy source for ethanol production. It is naturally cheap, plentiful and has high cellulose content. The sugarcane bagasse contains 34.5% cellulose, 24% hemicellulose, and 22-25% lignin. Reactive Oxygen Species (ROS), singlet oxygen (1O2), superoxide (O2-), hydroxyl radicals (OH?, and hypochlorite ion (OCl-), were found to remove both hemicellulose and lignin from sugarcane bagasse. Ox-B (Day. 2004, US Patent 6,866,870), a solution of sodium hypochlorite and hydrogen peroxide, was studied for its effectiveness as a pretreatment for lignocellulosic biomass. The cellulose structure of the bagasse was easily separated from the hemicellulose and lignin by filtration after Ox-B treatment. The remaining solids on a wet basis, were 76.2% digestible by cellulases, after a 20:1 treatment (v/w) with an Ox-B solution (10,000 ppm sodium hypochlorite : 500 ppm hydrogen peroxide). At a constant pH 8, 38.6% weight loss and 97.4% cellulose digestibility were observed. Temperature did not affect weight loss or cellulose digestibility. Above a 2% Ox-B treatment, cellulose digestibility was 100%. Cellulose digestibility increased with time for up to 3 h on treatment with Ox-B. Sequential treatments improved cellulose digestibility at lower concentrations of Ox-B. Treatment with Ox-B followed by a caustic wash produced solids that were between 80 and 100% digestible by cellulases. Our studies indicate that Ox-B is a powerful room temperature chemical oxidant that increases cellulose digestibility of sugarcane bagasse. Oxidation of bagasse, by sequential Ox-B treatments for 30 min, at a pH of 8 and room temperature, followed by a caustic wash may have industrial potential.