The objective of this paper is to review the published literature on improving properties of wood composites through thermal pretreatment of wood. Thermal pretreatment has been conducted in moist environments using hot water or steam at temperatures up to 180 and 230°C, respectively, or in dry environments using inert gases at temperatures up to 240°C. In these conditions, hemicelluloses are removed, crystallinity index of cellulose is increased, and cellulose degree of polymerization is reduced, while lignin is not considerably affected. Thermally modified wood has been used to manufacture wood-plastic composites, particleboard, oriented strand board, binderless panels, fiberboard, waferboard, and flakeboard. Thermal pretreatment considerably reduced water absorption and thickness swelling of wood composites, which has been attributed mainly to the removal of M. R. Pelaez-Samaniego

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Undebarked ponderosa pine chips were treated by hot water extraction to modify the chemical composition. In the treated pine (TP), the mass was reduced by approximately 20%, and the extract was composed mainly of degradation products of hemicelluloses. Wood flour produced from TP and unextracted chips (untreated pine, UP) was blended with high-density polyethylene (HDPE) and polypropylene (PP) and was extruded into wood plastic composites (WPCs). Formulations for WPCs consisted of 58% pine, 32% plastic, and 10% other additives. WPC based on HDPE+TP and PP+TP absorbed 46–45% less water than did WPC based on HDPE+UP and PP+UP, respectively. Thickness swelling was reduced by 45–59%, respectively, after 2520 h of immersion. The diffusion constant decreased by approximately 36%. Evaluation of mechanical properties in flexure and tension mode indicated improvements in TP-WPC properties, although the data were not statistically significant in all cases. Results showed that debarking of ponderosa pine is not required for WPC production.

Lowell, Eini C.; Rapp, Valerie A.; Haynes, Richard W.; Cray, Caitlin. 2010. Effects of fire, insect, and pathogen damage on wood quality of dead and dying western conifers. Gen. Tech. Rep.

Many socioeconomic constraints exist for biomass removals from federal lands in the western U.S. We examine several issues of importance, including biomass supply chains and harvesting costs, innovative new uses for bioenergy products, and the policy framework in place to provide incentives for biomass use. Western states vary greatly in the extent and utilization of forest resources, the proportion of land under federal ownership, and community and stakeholder structure and dynamics. Our research-which focused on the socioeconomic factors associated with biomass removal, production, and use-identified several important trends. Long-term stewardship projects could play a role in influencing project economics while being conducive to private investment. State policies are likely to help guide the growth of biomass utilization for energy products. New markets and technologies, such as biofuels, for use in the aviation industry, torrefied wood, mobile pyrolysis, and wood coal cofiring could greatly change the landscape of biomass use. Social needs of residents in wildland urban interfaces will play an important role, especially in an era of megafires. All of these trends-including significant unknowns, like the volatile prices of fossil energy-are likely to affect the economics of biomass removal and use in western forests.