13-02: Providing an optimized pretreatment methodology for utilizing low cost forest slash in biorefineries

When trees are cut for commercial harvest or thinning, the residues that are left behind on the forest floor or on the log landing areas after logging operations have taken place is called slash.  Forest slash consists mostly of tree branches, tops of trunks, stumps, branches, leaves and undergrowth.  Slash is generated at commercial sites in the forest, and also in the urban/wildland interface, at fuel reduction (or “thinning”) sites. Slash can be fed into an industrial grinder, and the resulting chips can be used as fuel to heat boilers in co-generating facilities. Slash is abundant in the Pacific Northwest and more than 3 mill metric ton are collected and used annually. Slash is typically rather wet (up to 50% water), the heat value of the slash as a boiler fuel is fairly low. We suggest to use the slash as a raw material for production of sugars for advanced biofuels and bioproducts and to include anaerobic digestion as the last process step after removal of the valuable sugars from the biomass material. Slash will contain both dirt and small stones even after downsizing as well as high concentration of bark which makes this material hard to process. In the presentation we will discuss an optimized outline for pretreating slash using the wet explosion technology which has yielded high concentrations of sugars after pretreatment and enzymatic hydrolysis as well as high methane production ensuring higher energy production than normally obtained by simple combustion of the whole raw material.