Arboriculture & Urban Forestry 37(1): January 2011 Arboriculture & Urban Forestry 2011. 37(1): 13–18 13 Wood Residue Processing and Utilization in Southeastern Michigan, U.S. Pascal Nzokou, Jessica Simons, and Anthony Weatherspoon Abstract. This paper is an analysis of southeastern Michigan, U.S.’s wood residue processing and disposal facilities. The analysis was conducted in order to characterize wood supply patterns, evaluate recovery efficiency, and identify potential alternatives for wood residues. Wood collection and processing facilities were identified and surveyed throughout a 14-county area. This study documented at least 180 wood residue yards operating in the region, which employed an average of six employees per yard (for a total of 1,082 employees in the industry). The total volume of wood entering the yards was quantified at 6,659.6 thousand cubic meters (5.3 million metric tons), mainly from land-clearing and tree removal. The wood residue supply was used to produce a total of 2,035.8 thousand cubic meter (1.6 million tons) tons of new products (e.g., wood chips, mulches, firewood), which were mainly sold locally. The overall conversion rate was estimated at 30% for the entire industry, clearly indicating room for improvement. The industry is estimated to contribute approximately USD $40 million to Michigan’s economy. Improvement of conversion rates and value-added product development would require fundamental changes in equipment, training, and processes used by tree service and land clearing companies. Keywords. Disposal Yards; Urban Tree; Wood Residue; Wood Residue Recovery. Wood residues include a large spectrum of wood products from primary and secondary processing such as bark, slabs, sawdust, chips, planer shavings, sander dust, end trims, used pallets, and construction residues. Wood residues also include logs, branches, and brush from urban tree removals, construction-related land clearing, farming, and industrial projects. Several studies and reports have indicated that large amounts of wood residues are generated annually in the United States. For example, in 2001, an estimated 234 million metric tons of residue was generated from traditional timber extraction, forest conversion to nonforest uses, primary processing, and demolition of buildings and struc- tures in the United States (McKeever 1998). A regional outlook indicates that the Midwest has 21.2 million tons of recoverable wood residues, including 2.2 million tons of municipal solid waste, 1.5 million tons from construction sources, 2.6 million tons from demolition, 5.6 million tons of logging residues, and 2.8 million tons of other types of woody residuals (McKeever 2003). Studies in other regions also report significant wood resi- due generation, showing that this is a nationally relevant issue (Hubing 1993; De Hoop et al. 1994; Short and Hooper 1996; Murphy et al. 2007). A more recent study reports that 7.5 mil- lion cubic yards of urban wood residues are generated annu- ally in the southeastern Michigan region alone, with 58% of the material being discarded (Sherrill and MacFarlane 2007). Wood residues are traditionally mulched and used for bed- ding, compost, or as fuel for energy. However, it is estimat- ed that wood residues accounted for about 17% of the total residues received at municipal landfills in the United States (Forest Products Laboratory 2002). Sherrill and MacFar- lane (2007) estimated that two million cubic yards of wood residue enters southeastern Michigan landfills each year. Wood residue recovery programs in Michigan and nationally are generally targeted towards low-end markets such as chips and mulches, which pay the equivalent of USD $0.25 for a recovered wood pallet, while products in the high-end markets, such as fin- ished solid wood products could pay 20 to 32 times more for an equivalent amount of wood (Forest Products Laboratory 2002). Studies have shown that there are several value-added op- tions for conversion of residue wood. For example, wood residues can be converted into wood fuel pellets for use in residential stoves or included as filler in the manufactur- ing of wood composites (Alderman et al. 1999). In addition, numerous researchers, local governments, and private busi- nesses have been successful in developing creative and profit- able uses for residue wood (Bratkovich 2001; Haviarova et al. 2001; Forest Products Laboratory 2002; Grushecky et al. 2006). The amount of wood residue generated in Michigan has re- cently changed due to the emerald ash borer (EAB) infestation, which killed more than 25 million ash trees across southern Mich- igan (Nzokou et al. 2006; McCullough and Siegert 2007). Previ- ous studies have discussed the potential for using residue wood generated from the EAB infestation in the fabrication of value- added products such as lumber for furniture, paneling, floor- ing, interior joinery, cabinetry, and pallets (Nzokou et al. 2006). An important and necessary step in developing profitable and viable markets for residue wood is to quantify the amounts that are available by source and type of material, analyze cur- rent production patterns, and identify the potential for alterna- ©2011 International Society of Arboriculture
January 2011
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