COMPOSTING OF WOOD WASTES: Plywood and Sawmill FWRC

Residue Forest & Wildlife Research Center RESEARCH ADVANCES

INTRODUCTION Wood waste disposal is becoming Research in the Forest and a huge problem for Mississippi’s Wildlife Research Center has forest products industry. The found ways to compost many of 1997 U.S. Census reports 892 these wastes and reclaim them for wood product manufacturers oper- value-added products. Studies by ating in Mississippi. These manu- Forest Products Laboratory scien- facturers cover all aspects of the tists Hamid Borazjani, Susan industry including furniture, paper, Diehl, and Harold Stewart have sawmills, and other wood prod- demonstrated that furniture scraps ucts. A survey of 376 wood prod- and waste, plywood waste, and ucts manufacturing companies hardwood / sawmill residue can conducted by MSU’s Food and be successfuly composted. Fiber Center in 1994 revealed that there were 12.2 million tons of Composting is an aerobic biologi- wood and bark residues produced cal treatment process which con- annually in Mississippi. verts solid organic material into a stable humus at elevated temper- Small manufacturers that do not atures (40 - 60oC). Composting have the capability to burn the wood waste reduces the waste wood waste for energy must volume, detoxifies the waste and transport it elsewhere for incinera- transforms the waste into a prod- tion or to a landfill. Because of uct that can be used as a soil high transportation costs, landfill amendment. Composting increas- costs, environmental concerns, es the organic matter content and and governmental regulations, improves the water-holding capac- alternative methods of disposal ity and the texture of the soil. A are being sought. One alternative composting operation can be is the composting of wood waste. implemented at a plant site and requires limited knowledge, equip- ment, and space. M E T H O D S Chicken manure amended treatments showed the best results in reduction of toxicity, weight Two recent studies investigated composting of loss, and color change. hardwood sawdust / bark waste, and phenolic bonded softwood plywood waste. Amendments The treatments were then evaluated in a green- included chicken manure, cow manure, horse house study to determine if the composted manure, gin trash and inorganic fertilizer. material could be used as a soil additive. Soybeans, cotton, and corn were grown in the An additional objective of these projects was to various treatments for 55 days. At the end of the specifically evaluate the effectiveness of chicken cycle, the plants weights were measured and manure in composting. In 1999, Mississippi’s recorded. Once again, chicken manure proved poultry industry produced 600,000 tons of litter. to be the only treatment comparable to commer- Composting was viewed as a way to dispose of cial potting media (Figure 2). both wood wastes and chicken litter in an envi- ronmentally friendly and economical way. According to the 1997 U.S. Census, there are 138 sawmills operating in Mississippi. These In the plywood waste study, a pilot-scale com- sawmills produce huge amounts of sawdust and posting operation was set-up to test different bark waste. In order to alleviate the industry of amendments to sawdust obtained from a furniture this waste residue, a hardwood sawdust and company in Mississippi. Eighteen containers bark waste study was initiated. were filled with sawdust and amendments. The amendments were 5% chicken manure, 5% cow In this study, chicken manure was added to hard manure, 5% horse manure, 3% cotton gin trash, wood sawdust collected from a sawmill in and one liter of inorganic fertilizer solution. Mississippi. The chicken litter was added in per- centages (10, 20, and 30 percent), aerated and The compost cans were placed outdoors for six watered weekly. All percentages of added chick months. The treatments were aerated once or en manure were well composted and showed twice per week depending on rainfall and the significant weight loss in 90-days. The compost moisture content was is currently kept at 50%. At the being evaluated end of 180 days, all as a commer- treatments showed a cial potting decrease in toxicity media to be and weight (Figure 1). used by nurs- eries in South Mississippi. P R O C E D U R E S 35

Composting is a relatively simple operation and 30 has been an agricultural practice for many years. Several area wood manufacturers could combine 25 their resources and build a large-scale, compost- ing site and supply local farmers and nurseries 20 with the product. Plant owners who want to have a composting site on their property need a 15 grinder, mixer, and a tractor or means to mix the compost rows or piles. Lumber mills, construc- 10 tion companies, furniture companies, and dry wall businesses may find composting could be an Sawdust + Gin Trash

5 Sawdust + Cow Manure Sawdust + Horse Manure

effective alternative for disposal. Composting Sawdust Only Sawdust + Chicken Manure removes the toxins in wood that can be detrimen- tal to plant growth and produces a stable product 0 that can be used as a soil conditioner or mulch. Treatment The addition of chicken manure allows wood to Figure 1. Average percent of total weight lo decay faster and increases the nitrogen content the composted plywood sawdust at day 180 of the end product. 3 Nurseries and farmers can mix the compost with other soil as an additive. The composted wood 2.5 waste has been demonstrated to be an effective media in both row crops and ornamental plants. 2

1.5

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0.5 Commercial Media Chicken Manure Sawdust Only Horse Manure 0 Cow Manure Inorganic Fertilizer Treatment

Figure 2. Mean dry weights (grams) of row plants from greenhouse study. http://www.cfr.msstate.edu Research conductedby Mississippi State,MS39762 religion, national origin, sex, [email protected] on thebasisofrace, color, Karen Brasher, Editor Mississippi StateUniversity Fax: 662-325-8726 information contact: Harold A.Stewart does notdiscriminate Hamid Borazjani Research Center Forest &Wildlife Interim Director age, disabilityor 662-325-2952 FWRC-FP-188 Susan Diehl veteran status. Bob L.Karr,

Box 9680 RESEARCH For more ADVANCES

August 2000 Vol. 5, No. 1 FUTURE RESEARCH FUTURE annually inMississippibythe scrapped palletsweregenerated in 1994revealedthat149,000 by MSU’s Foodand FiberCenter Mississippi. Asurveyconducted pallet manufacturersin There are57woodcontainerand focus oncompostingusedpallets. wood wastes.Next,researchwill hardwood sawmillwastesandply- composting furniturewoodwastes, Scientists havebeensuccessfulat disposal. be aneconomicalalternativefor Composting ofusedpalletsmay to thewoodproductsindustry. pallets arebecomingburdensome ernmental regulations,scrapped environmental concernsandgov- fill costs,transportation or reused.Duetoincreasedland- lets, only7%werebeingutilized industry. Ofthesescrappedpal- wood productsmanufacturing