Partially Hydrolyzing Southern Hardwoods: Possibilities for Biofuels and Wood Composite Manufacturing T. Eric McConnell Sheldon Q. Shi Abstract Conversion of lignocellulosic materials, including wood, to fuel is currently cost prohibitive due to the expenses involved and the lack of value addition, even though small-diameter hardwoods are readily available. Alternative processes therefore need to be investigated. Partially hydrolyzing wood may offer an opportunity to add value to the conversion process by producing a modified woody by-product that can be used as a wood composite raw material. Experiments were conducted on the effects of a partial hydrolysis on the mass loss, specific modulus, and surface free energy of modified southern hardwoods, and this article reports the changes in holocellulose content of water-saturated yellow-poplar (Liriodendron tulipifera L.), sweetgum (Liquidambar styraciflua L.), and red oak (Quercus spp.) heated at 1508C for 30 minutes in three solutions: 1 percent sulfuric acid, deionized water, and 1 percent sodium hydroxide. The treated woods were compared with untreated controls. The previously tested wood samples were ground to a size 20 mesh, and holocellulose content was analyzed gravimetrically. Properties of the modified wood were then regressed on holocellulose content following partial hydrolysis. All three treatments significantly reduced the holocellulose content in each species, with the greatest reduction obtained in the acid treatment, followed by the alkaline solution treatment and the deionized water treatment, respectively. The changes in holocellulose explained a majority of the variation in mass loss due to treatment and specific modulus, whereas surface free energy was poorly explained by changes in the wood structure. Implications for wood composites manufacturing are discussed. Conversion of lignocellulosic materials, including wood, to ethanol has become a primary agricultural policy concern. Low-valued small trees from southern hardwood species can provide an excellent feedstock source for biorefineries. These stems are primarily early to mid successional species, such as red oak (Quercus spp.), sweetgum (Liquidambar styraciflua L.), and yellow-poplar (Liriodendron tulipifera L.), among others, that compete with southern pine (Pinus spp.) on many sites. Rather than adding cost to their timber investment by applying expensive silvicultural treatments, landowners can have these stems harvested for biofuel conversion. The refining process, however, completely hydrolyzes the lignocellulosic material to maximize sugar yield by using a combination of extreme temperatures and harsh chemicals. A by-product consisting of mainly lignin, which currently has little commercial value, is primarily burned for energy onsite (Garrote and Parajo 2002). High input costs coupled with low output revenues due to a lack of added value being realized from the conversion process currently leave lignocellulosic ethanol cost prohibitive. Therefore, an alternative lignocellulosic conversion process needs to be investigated to provide added wealth to the landowner, productivity to the logger, and revenue streams to the production facility. One option would employ relatively low temperatures and chemical concentrations, which would only partially hydrolyze the wood. This would result in forming some hydrolyzed sugars to ferment for conversion to ethanol while leaving behind a modified wood by-product that remains structurally whole rather than being pulped to individual fibers. This by-product could add value to the conversion process as a raw material, with possibly improved properties, for wood composites. However, few studies have been conducted on wood properties following treatment in a heated solution (Hill 2006, Ragauskas et al. 2006). Wood heated in solution under pressurized conditions undergoes many mechanical, physical, and chemical modifications due to changes in the chemistry of the wood cell wall brought about by hydrolysis. The extractives are the first constituents removed, because they are nonstruc- The authors are, respectively, Assistant Professor and Extension Specialist, School of Environment & Natural Resources, The Ohio State Univ., Columbus (mcconnell.213@osu.edu); and Associate Professor, Dept. of Forest Products, Mississippi State Univ., Mississippi State (sshi@cfr.msstate.edu). This paper was received for publication in January 2011. Article no. 11-00014. ÓForest Products Society 2011. Forest Prod. J. 61(3):235–239. FOREST PRODUCTS JOURNAL Vol. 61, No. 3 235