Pretreatments and energy potentials of Appalachian hardwood residues for biofuel production
Continuous increase in crude oil price and environmental issues related to toxic emissions from the use of petroleum products has necessitated the need to find an alternative renewable source of energy in woody biomass. Accordingly, properties, chemical pretreatments, and enzymatic hydrolysis of logging residues to fermentable sugars were evaluated in this study. Logging residue specimens of yellow-poplar (Liriodendron tulipifera) and red oak (Quercus rubra) were collected from fifteen previously harvested sites across West Virginia and then analyzed for their physical, chemical, and thermal properties. Results indicated that logging residues of yellow-poplar and red oak were dried in nature to a moisture content that ranged from 7.4% to 39%. Chemical analysis showed higher extractives and lignin contents for decayed wood samples collected in 2005 harvested sites. Heating value showed no significant difference between sapwood and heartwood residues of undecayed and decayed logging residues.
The effects of low alkali mixtures and hydrogen peroxide solutions at 80°C over variable cook time were evaluated on sound and decayed wood residues of yellow-poplar and red oak using two chemical treatments: (1) ammonium hydroxide and sodium hydroxide (ASO) and (2) hydrogen peroxide/ammonium hydroxide and sodium hydroxide (PASO) mixture. Effects of ultrasonication, microwave and hydrogen peroxide prior to enzymatic hydrolysis was also evaluated on yellow poplar residue. Results indicated wood hydrolysis rate increases with an increase in sodium hydroxide concentration and cook time for ASO and PASO chemical treatments on all wood residues. All observed alkali treatments showed little or no effect on the decomposition of lignin content of wood residues. Measured sugar content after alkali treatments and enzymatic hydrolysis ranged from 50 to 81 mg/ml from ASO/PASO treated yellow poplar and red oak residues. Enzymatic hydrolysis of ASO and PASO treated residues hydrolyzed approximately 61% of the original wood content, while over 80% of hardwood pulp fibers and paper wastes were digested to sugar.
Ultrasonication reduced wood particles into nano scale sizes. During the chemical pretreatment wood, constituents were progressively hydrolyzed (ranged from 20–100%) with increases in temperature within 10 minutes of cook time in the microwave into high molecular weight sugars. Hydrolysis of wood particles in the pretreatment chemical was directly proportional to temperature and time, regardless of particle size. Sugar production via enzymatic hydrolysis from pretreated yellow-poplar residue gave comparable glucose yield range of 80 to 110 mg/ml when compared to lignin free cellulose.
Natural Resource Management;
0528: Natural Resource Management
0746: Wood sciences