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Ensilage is a truncated solid-state fermentation in which anaerobically produced organic acids accumulate to reduce pH and limit microbial activity. Ensilage can be used to both preserve and pretreat biomass feedstock for further downstream conversion into chemicals, fuels, and/or fiber products. This study examined the ensilage of enzyme-treated corn stover as a feedstock for particleboard manufacturing. Corn stover at three different particle size ranges (<100, <10, and <5 mm) was ensiled with and without a commercial enzyme mixture having a cellulase:hemicellulase ratio of 2.54:1, applied at a hemicellulase rate of 1670 IU/kg dry mass. Triplicate 20 L mini-silos were destructively sampled and analyzed on days 0, 1, 7, 21, 63, and 189. Analysis included produced organic acids and water-soluble carbohydrates, fiber fractions, pH, and microorganisms, including Lactobacillus spp. and clostridia were monitored. On days 0, 21, and 189, the triplicate samples were mixed evenly and assembled into particleboard using 10% ISU 2 resin, a soy-based adhesive. Particleboard panels were subjected to industry standard tests for modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IB), thickness swell (TS), and water absorption at 2 h boiling and 24 h soaking. Enzyme addition did improve the ensilage process, as indicated by sustained lower pH (P < 0.0001), higher water-soluble carbohydrates (P < 0.05), and increased lactic acid production (P < 0.0001). The middle particle size range (<10 mm) demonstrated the most promising results during the ensilage process. Compared with fresh stover, the ensilage process did increase IB of stover particleboard by 33% (P < 0.05) and decrease water adsorption at 2 h boiling and 24 h soaking significantly (P < 0.05). Particleboard panels produced from substrate ensiled with enzymes showed a significant reduction in water adsorption of 12% at 2 h boiling testing. On the basis of these results, ensilage can be used as a long-term feedstock preservation method for particleboard production from corn stover. Enzyme-amended ensilage not only improved stover preservation but also enhanced the properties of particleboard products.

Increased demand for wood adhesives, environmental concerns, and the uncertainty of continuing availability of petrochemicals have led to recent attention on protein-based adhesives. This study was conducted to investigate the glue bond qualities of soy-based phenolic adhesive resins for southern pine plywood. Two types of soy-based resins were formulated and tested. The first was made by cross-linking soy flour with phenol-formaldehyde (pf) resins at neutral pH. The second type was obtained by cross-linking soy flour hydrolyzates with pf resin under alkaline conditions. Plywood bonded with the neutral phenolic soy resins containing 70% soy flour and 30% 1.6 g/cm 2 pf without the use of extenders and fillers compared favorably with the traditional southern pine pf glue mixes. Plywood bonded with alkaline phenolic soy resins, containing 40 or 50% 0.5 g/cm 2 PF with the addition of extender (19% corn-cob powder), provided better adhesive glue bond properties than traditional southern pine pf glue mixes. These results suggest that soy-based phenolic adhesive resins have potential for the production of exterior southern pine plywood.Paper no. J11114 in JAOCS 83, 231-237 (March 2006). KEY WORDS:Exterior-grade adhesives, phenol-formaldehyde, plywood, soy-based phenolic adhesives, soy flour hydrolyzate.Before the advent of modern synthetic adhesive resins, such as urea-and phenol-formaldehyde resins, soy glues were important adhesives for plywood production. Uncertainty about the future supply of petrochemicals and stringent regulations on toxic emissions have compelled wood industries to develop adhesive resins from renewable resources. Agricultural industries are also eager to invest in researching nonfood uses of agricultural products to expand their markets. Carbohydrates and proteins are the most abundant renewable substances suitable for uses as wood adhesives. It is a significant challenge to develop adhesives from these natural substances at a reasonable cost that can compete with synthetic thermosetting adhesives and meet stringent performance requirements. A current concept to achieve this goal is to use these natural substances as copolymers with synthetic polymers to reduce the dependency on petroleum-derived chemicals. In this respect, proteins are more suitable than carbohydrates because amino, carboxyl, aliphatic and aromatic hydroxyl, and other functional groups in proteins provide various functionalities for chemical cross-linking.The use of proteinaceous materials, such as blood, casein and soybean, as adhesive glues was common in the middle of 20th century. Golick and Dike (1) formulated exterior phenolic plywood glues containing up to 70% dried blood. Ash and Lambuth (2) prepared plywood glues containing a high content of blood solids blended with phenol-formaldehyde (PF) resins. Weakley and Mehltretter (3) developed moisture-resistant plywood adhesives by cross-linking casein with dialdehyde starch. The use of soy-based glues derived from the discoveries of Davidson was quite popular until 1960 (4)....

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