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The production of six regionally important cellulosic biomass feedstocks, including pine, eucalyptus, unmanaged hardwoods, forest residues, switchgrass, and sweet sorghum, was analyzed using consistent life cycle methodologies and system boundaries to identify feedstocks with the lowest cost and environmental impacts. Supply chain analysis was performed for each feedstock, calculating costs and supply requirements for the production of 453,592 dry tonnes of biomass per year. Cradle-togate environmental impacts from these modeled supply systems were quantified for nine mid-point indicators using SimaPro 7.2 LCA software. Conversion of grassland to managed forest for bioenergy resulted in large reductions in GHG emissions due to carbon uptake associated with direct land use change. By contrast, converting forests to cropland resulted in large increases in GHG emissions. Production of forest-based feedstocks for biofuels resulted in lower delivered cost, lower greenhouse gas (GHG) emissions, and lower overall environmental impacts than the agricultural feedstocks studied. Forest residues had the lowest environmental impact and delivered cost per dry tonne. Using forest-based biomass feedstocks instead of agricultural feedstocks would result in lower cradle-to-gate environmental impacts and delivered biomass costs for biofuel production in the southern U.S. [ABSTRACT FROM AUTHOR]

Biomass pretreatment by autohydrolysis uses hot-water to extract soluble components from wood prior to converting the woody residuals into paper, wood products, or fuel, etc. Mixed hardwood chips were autohydrolyzed in hot-water at 150, 160, 170, and 180 ºC, for 1 and 2 h. The tradeoff between fermentable sugar yield and caloric value of the residual solids was studied for a process that will be referred to as "value prior to combustion". The extracted liquid was treated with dilute sulfuric acid to break down sugar oligomers into fermentable monomers. Material balances were performed around autohydrolysis to evaluate the role of temperature and residence time on sugar production and residual solid heating value. The composition (sugars and byproducts) of the extracted liquid was determined. As the autohydrolysis temperature increased, the material balance became less precise, presumably due to more volatile byproducts being formed that were not quantified. More hemicelluloses were extracted from the wood by the hot water extraction process under higher temperature and longer residence time, but a greater degree of sugar degradation was also observed. After hot-water extraction the heating value of the solid residues was higher than the original wood. The total energy content of the residual solid after extraction ranged from 74 to 95% of the original energy content of the feed. [ABSTRACT FROM AUTHOR]