(608d) High Efficiency Feedstock Fractionation With the Avap® Biorefinery Technology

A significant techno-economic barrier for commercial implementation of renewable transportation fuels and biobased chemicals derived from lignocellulosic biomass has been the natural resistance, or recalcitrance, of biomass to decomposition. American Process Inc. has overcome this hurdle with our patented AVAP® biorefinery technology. AVAP efficiently fractionates biomass into nearly pure individual component streams of hemicellulosic sugars, glucose (from cellulose), and lignin using sulfur dioxide (SO₂) and ethanol in a proprietary process configuration.

The effectiveness of the AVAP fractionation process is based on the unique kinetics offered by the combination of SO₂, ethanol, and water. The kinetics of AVAP delignification, polysaccharides removal and cellulose hydrolysis were studied extensively. During the initial phase of fractionation, the hemicelluloses removal and cellulose hydrolysis rates were found to be related to the first-order delignification rate, while in the following bulk phase they proceed independently. We propose that during the initial phase, the hemicelluloses are removed together with lignin in the form of lignocarbohydrate complexes, while cellulose is protected by lignin from hydrolytic attack. Selectivity of the process can be adjusted across a wide range depending on the intended products.

The unique combination of SO₂ (delignifying agent) with ethanol (penetrating solvent) makes AVAP suitable for all feedstocks evaluated to date including hardwood, softwood, corn cobs, corn stover, switchgrass, energy cane, sugar cane straw, eucalyptus and miscanthus. The cellulose (95% pure) is enzymatically converted to glucose with very low enzyme dosage. Hemicelluloses are autohydrolyzed without addition of acid to monomers. Lignin is removed from the process and burned, making AVAP a net energy (power) exporter. Fractionation chemicals are recovered in an energy efficient manner for reuse. Overall and carbohydrate mass balances show no carbohydrate losses as further supported by very low amounts of formed oxidation and dehydration products. The AVAP process is currently being demonstrated for production of cellulosic sugars and cellulosic ethanol at our fully integrated 3.5 bone dry tons per day AVAP® Biorefinery in Thomaston, Georgia.