Ethanol production from various agricultural and forest residues has been widely researched, but there is limited information available on the use of mixed hardwood for ethanol production. The main objective of this study is to assess the impact of time on the steam explosion pretreatment of waste wood (mixed hardwood) and to determine the convenience of a delignification step with respect to the susceptibility to enzymatic hydrolysis of the cellulose residue and the recoveries of both cellulose and hemicellulosic sugars. Delignification did enhance enzymatic hydrolysis yields of steam exploded waste wood. For steam explosion pretreatment times of 3 and 5 min, the recovery yield of hemicellulosic-derived sugars decreased. The effective hemicellulose solubilization does not always result in high recoveries of hemicellulose-derived sugars in the liquid fractions due to sugar degradation. In the steam explosion pretreatment times of 3 and 5 min, where hemicellulose solubilization exceeded 95%, but sugar recoveries in the liquid fraction remained below 30%. Cellulose to glucose yield losses were less significant than hemicellulosic-sugar losses, with a maximum loss of 24% at 5 min. Up to 80% of the lignin in the original wood was solubilized, leaving a cellulose-rich residue that led to a concentrated cellulose to glucose yield solution (about 50 g/L after 72 h enzymatic hydrolysis in the best case). The maximum overall process yield, taking into account both sugars present in the liquid from steam explosion pretreatment and cellulose to glucose yield from the steam exploded, delignified and hydrolyzed solid was obtained at the lowest steam explosion pretreatment time assayed.

Introduction
Materials and Methods
    1. Raw material
    2. Steam explosion pretreatment
    3. Alkaline peroxide delignification
    4. Enzymatic hydrolysis
    5. Analytical methods
Results and Discussion
    1. Raw material composition
    2. Steam explosion pretreatment
    3. Alkaline peroxide delignification
    4. Enzymatic hydrolysis
    5. Overall process yields
Acknowledgement
References

• Si Young Ha(Research professor, Department of Environmental Forest Science/Institute of Agriculture and Life Science, Gyeongsang National University, Jinju, 52828, Korea)
• Hyeon Cheol Kim(Master course, Department of Environmental Forest Science/Institute of Agriculture and Life Science, Gyeongsang National University, Jinju, 52828, Korea)
• Woo Seok Lim(Undergraduate, Department of Environmental Forest Science/Institute of Agriculture and Life Science, Gyeongsang National University, Jinju, 52828, Korea)
• Jae-Kyung Yang(Professor, Department of Environmental Forest Science/Institute of Agriculture and Life Science, Gyeongsang National University, Jinju, 52828, Korea) Corresponding author