Abstract
Different operating conditions are required to optimize the yield from each of the various fractions in the substrate. Xylose recovery is maximized at short cooking times whereas maximum lignin recovery requires much longer cooking times. Peak glucose yield and rumen digestibility occur at intermediate times. If process conditions are set for maximum glucose yield we have achieved a yield of 68% of the theoretical, based on an average of a dozen substrates tested. Individual results ranged from 46 to 87%. If the process is optimized for maximum total sugars (i.e. glucose plus xylose) we have obtained an average yield of 60%, with a range of 31 to 75%. With rumen microflora, the average value of the in-vitro cellulose digestibility was 82%, with a range of 41 to 90%. The optimum operating conditions for total sugars are a pressure of 500 to 550 psig with a cooking time of 40 to 50 seconds and 35% starting moisture content. Particle size is not a significant factor, nor is pre-steaming or use of a constricting die in the gun nozzle. High quality lignin can be extracted with 80% yield. The Iotech lignin is very soluble, has a low molecular weight and is reactive.more » The unique properties of the lignin derive from the explosion at the end of the pretreatment. A lignin formaldehyde resin has been successfully formulated and tested. It represents a high value utilization of the lignin byproduct with immediate market potential. A detailed engineering design of the process gives an estimated operating cost of $7.50/OD ton of biomass. At this low cost, the Iotech process achieves many important pretreatment goals in a single step. The substrate has been sterilized; it has been pulverized into a powder; the cellulose has been accessible; and a highly reactive lignin fraction can be recovered and utilized. « less