Steam explosion of sugarcane bagasse as a pretreatment for conversion to ethanol

The State of Hawaii is interested in converting the large volume of agricultural residues, principally sugarcane bagasse, that is generated in the state into transportation fuels. One of the technologies that is currently being evaluated is steam explosion as a pretreatment for conversion of the bagasse into ethanol. In order to identify the optimum conditions of the steam explosion cycle, a range of operating temperatures (188–243°C) and residence times (0.5–44 min) were used to pretreat bagasse in a 10 l batch reactor. The analytical results were also used to evaluate the “reaction ordinate” concept. The exploded bagasse samples were examined as to total mass recovery, weight loss by water extraction, composition of water extracts, total sugar recovery, and conversion of the polysaccharide of the exploded biomass to monosaccharide by a cellulosic enzyme mixture. Steam explosion followed by enzymatic saccharification was found to be an effective pretreatment for converting biomass into monosaccharides. However, the total sugar recovery, and thus the ethanol “potential”, of the process was relatively insensitive to changes in reaction conditions due to the trade-off between xylose recovery and glucose recovery. Furthermore, it was found that the reaction ordinate concept was not universally valid for the variety of sample characteristics examined in this study.