| Due to climate change and the gradual depletion of fossil fuel, there is a renewed interest in bioenergy for sustainable energy production and economic development. Biofuel meets sustainable economic development by reducing carbon dioxide emissions."Second-generation bioethanol", based on lignocellulose biomass, does not compete with feed and food for feedstock. However, lignocellulosic materials is a structural materials that has natural resistance to enzyme and microbial destruction, alled"recalcitrance". Pretreatment can of lignocelluloses biomass can change cell wall structure to reduce its recalcitrance. However pretreatment is energy intensive especially applied to woody biomass. It is important to find a pretreatment process with low energy consumption and easily scalabke for commercialization. SPORL is such process for its low energy consumption and excellent scalability practiced by the pulp and paper industry.In this dissertation, we first studied the energy consumption for woody size-reduction. The approach of post-chemical pretreatment wood size-reduction using disk milling was adopted. The conditions of pretreatment and disk milling were investigated, to reduce milling-energy consumption and increase enzymatic hydrolysis glucose yield (EHGY) from pretreated solid substrate. In low pH value SPORL process, most of hemicelluloses were removed by H2SO4, and lignin was sulfonated and swelled by sodium bisulfite. As a result, milling-energy consumption was reduced by more than 80 percent, and EHGY of 90% was achieved. Milling-energy consumption can be significantly reduced by increasing disk gap or decreasing milling solids loading. For a low pH value SPORL process under conditions of 2.2% H2SO4 and 8.0% NaHSO3 (both based on o.d. wood chips), 0.76 mm disk gap, and 10% milling solids loading, disk milling energy consumption was only about 45.8 Wh/kg(based on o.d. wood chips) while achieving a substrate enzymatic digestibility of over 90%. We found that there is a function relationship between milling-energy consumption and glucose yield from unit energy consumption. The equation is: where y, x, are glucose yield from unit energy consumption, milling-energy consumption, respectively. While A is a EHGY, glucose yield from 1 kg untreated wood chips after pretreated (g/kg)The dissertation also conducted a preliminary analysis of ethanol production mass and energy balance. Lodgepole pine was pretreated by SPORL process. Solid substrate was fermented by SSF process. The SPORL spent liquor that contains mainly hemicelluloses sugras was separately fermented after detoxification using an XAD-4 resin column. S. cereyisiae D5A (ATCC culture collection, ATCC? 200062) was used for fermentation. The highest ethanol yield of 276 L/ton (based on o.d. untreated wood chips) was achieved, or about 72% theoretical. The pretreatment conditions of the highest total ethanol yield were 2.2% H2SO4 and 8.0% NaHSO3 (both based on o.d. wood chips). Based on preliminary energy audit, a net ethanol energy output was 4.55 GJ/ton (based on the highest total ethanol yield, and energy from lignin not included).This dissertation also conducted SPORL pretreatment optimization for aspen. The optimum conditions for SPORL pretreatment of aspen were: H2SO4 of 2.2% and NaHSO3 of 8.0% (both based on o.d. wood chips), reaction temperature of 170℃, duration time of 20 min, then milled at 0.76 mm disk gap, and 10 milling loading. Subsequent disk milling-energy consumption was 20.7 Wh/kg (on o.d. wood chips) and substrate cellulose enzymatic digestibility (SED) was nearly 100%. Xylose and mannose, disssolved in spent liquor, were 112.2 and 11.4 g/kg (both on o.d. untreated wood chips).
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