To utilize recalcitrant agricultural residues a pretreatment of material is necessary to release small molecules needed as substrates from the various matrices of the plant. Pretreatment involves a mixture of mechanical, chemical, and enzymatic procedures that physically and chemically separate plant components.
Basic mechanical treatments include chipping and grinding material and is already part of the GVCS 50.
High and low pH is used to drive lignocellulose separation and degradation through the addition of bases and acids respectively. Acid Steam Explosion is an established protocol for pretreatment, though Ammonia Fiber Expansion has been refined more recently.
Arguably enzymatic pretreatments could be utilized on a small distributed scale with utilization of the proper catalytical organisms and judicious process design. A bioreactor with membrane purification system may be well suited to production of hydrolytic enzymes from a variety of saprophytes which could be used to extend the feedstock for production of materials or chemicals. An example of such a system could be with the well studied fungal saprophyte Trichoderma reesei that secretes 37 hydrolytic enzymes which degrade the cellulose, hemicellulose, and lignin making up plant cell walls. Trichomderma could be inoculated with an agricultural waste product and allowed to grow with a constant bleed of media through a microfiltration membrane, which will separate secreted ezymes from the cells and will remove hydrolytic reaction products alleviating product formation inhibition. Clarified enzyme mix could then be incubated with feedstock (which may require mechanical and chemical pretreatment first) that will be used by another microorganism for fermentation. After sufficient time of the enzyme treatment the degraded plant material, is possibly mixed with a more sugar rich feedstock, and inoculated with a productive microorganism for fermentation.