Reducing acid use in pre-treatment of cellulosic biomass through mineral removal

Background: Biomass contains cellulose wrapped in a recalcitrant lignin and hemicellulose sheath that must be chemically and/or physically disrupted in a pretreatment step. One of the most common pretreatments involves exposure of the biomass to dilute acid at elevated temperatures. Usually sulfuric acid is employed (rather than nitric or hydrochloric acid) because of its low cost. However pretreatment expenditures are large even when sulfuric acid is used because substantial quantities of acid are required neutralization and disposal costs are significant and containment costs are high. It has been discovered that biomass contains a significant mineral content and that these minerals neutralize some of the pretreatment acid which increases acid demand. Specific to sulfuric acid is an equilibrium shift where formation of bisulfates (HSO4) in addition to sulfates (SO42) reduces hydrogen ion concentration and compounds the effect of neutralization. This equilibrium shift has a more pronounced effect at lower acid concentrations where the amount of hydrogen ion consumed represents a large percentage of the total hydrogen ion concentration. Further bisulfate salt formation is favored when the acidic solutions are subjected to the high temperatures used for pretreatment reactions. Due to bisulfate salt formation which is exacerbated at high temperatures the concentration of acid required to achieve a particular reaction rate is increased. Technology Description: Dartmouth inventors have developed an approach to remove minerals from the biomass prior to pretreatment. This step reduces the amount of acid needed for the pretreatment step thereby reducing the cost of pretreatment. Applications: Biomass