Sulfur dioxide combined with steam is particularly effective as a pretreatment for enzymatic cellulose saccharification. Recent advances in the chromatographic separation of strong acid hydrolyzate has improved the economics of the process. Advancements in cross-linked plastic coatings allow the use of lower cost materials in equipment selection and construction and with the lower temperature allowed by higher acid concentration, one can use near atmospheric pressure process operations. The integration of commercial chromatographic separation equipment allows the near complete recovery of the acid catalyst without large energy penalties. Both environmental and genetic engineering have produced bioorganisms which readily metabolize both C5 and C6 sugars produced from the lignocellulose.
Separation recycles the acid for reconcentration and sugar for neutralization and nutrient addition.
Clear sugar streams allow the recovery of bio-organisms for recycle as well as the recovery of reusable water from the distillation column bottoms. They have several international patents pending on the process and are pursuing international as well as domestic development opportunities. The first plants should be financed and starting construction by late 1996 or early 1997.