ARE produces bioethanol by using small fiber cellulosic feedstocks from two potential sources: 10 m–1 mm fibers from the biogas digester or > 1 mm fibers from the drum separator. These are pretreated with NaOH and Urea-EDA solution to break the lignin and hemicelluloses by maceration, neutralized, and then fermented with yeast to produce ethanol. The ethanol is then distilled and dehydrated.
Owing to the recalcitrant nature of lignocellulosic biomass, caused by various factors like lignin carbohydrate matrix, cellulose crystallinity, cellulose accessible surface area, and sheathing by hemicellulose, pretreatment (either chemical or mechanical) is necessary to enhance the substrate conversion / digestion with enzymes. In general, alkaline (sodium hydroxide) and ammonia pretreatment cleaves the ester linkages between carbohydrates and lignin, and thus, more carbohydrates are exposed to the enzymatic reactions.
The pretreated substrates are then subjected to simultaneous saccharification and fermentation, which is thought to be the best process for enzymatic conversion of cellulose for ethanol production using ethanol tolerant / thermotolerant yeast strains like Saccharomyces sp. / Kluyveromyces sp., or strains genetically engineered for maximum ethanol production. The SoilNet LLC fiber treatment for cellulosic sugar process uses a unique one-state, one minute process to activate cellulosic biomass followed by conversion to glucose at very low enzyme loading, while maintaining the lignin intact.
Followed by fermentation, the undigested / unfermented residues containing cellmass and lignin is filtered with polymers added to enhance the filtration rate by forming pellets. Basically, the added polymers help to agglomerate the solids, which in turn will increase the filtration rate. The recovered solids (coated with polymers) are used in the formulation of valuable organic fertilizer to be spread on agricultural fields. Following fermentation, using conventional ethanol recovery processes, such as azeotropic distillation and molecular sieve dehydration, for the maximal recovery of fuel-grade ethanol for transportation. The ethanol produced is then distilled and dehydrated.
