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Abstract

Method of treating biomass material wherein it is subjected to two stage hydrolysis in which in first stage, the more easily hydrolyzed polysaccharides, such as hemicelluloses, are depolymerized and in second stage the more difficultly depolymerizable material, e.g., cellulose, is depolymerized. The biomass material is preferably subjected to a sensitization step between the first and second hydrolyzing stages by contact with molecular oxygen. The resulting hydrolysate and remaining solids are variously treated, including recycling of hydrolysate to first stage hydrolysis; countercurrent or co-current flow of recycled hydrolysate is carried out according to the nature of solids; acid is added at appropriate points, preferably nitric acid to provide nutrients for fermentation or to inhibit corrrosion of equipment; bases such as calcium carbonate or hydroxide are added to neutralize hydolysate for fermentation; wet oxidation and methanation are carried out to solubilize refractory solids (wet oxidation) and to produce methane (methanation); and ferric and/or aluminum ions are added to flocculate solids in the hydrolysate and such ions are recovered and resolubilized by wet oxidation and are routed to the hydrolysis stages to function as catalysts.

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