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ABSTRACT
In a 6-month composting study, sawdust from machined softwood plywood bonded with phenol-formaldehyde resin was amended with chicken manure, cow manure, horse manure, cotton gin trash, and inorganic fertilizer. The sawdust and amendments were placed in eighteen 75-liter plastic cans. Moisture was provided through atmospheric precipitation, and the substrate was aerated once or twice per week, depending on the amount of rainfall. Samples were collected at 30-day intervals and analyzed for toxicity and pH. On day 180, the compost cans were weighed and sampled to determine the decrease in dry weight. All treatments showed a signif icant decrease in toxicity by day 180, and maintained a neutral pH throughout the study with the exception of the horse manure treatment. All treatments showed a reduction in weight. Amended treatments had almost double the percentage of weight loss compared to the unamended control. The composted sawdust was also evaluated in a greenhouse study to determine its effect on the growth of row crop plants. Twenty-five percent of the composted sawdust by weight was mixed with potting soil, in which com, soybean, and cotton seeds were planted. The pots were watered daily and allowed to grow for 55 days. The chicken manure treatment showed no significant difference in mean dry weight of the plants compared to potting soil. Other treatments were comparable to chicken manure, except gin trash, which showed a significantly lower dry weight for plants compared to the chicken manure and control.
Total North American production of plywood and oriented strandboard (OSB) is expected to grow from 37.5 billion ft.2 in 1998 to 38.8 billion ft.2 in 2002 (1). This increase in demand will result in the generation of more woodwaste for disposal. Most of these woodwastes are currently energy sources for large OSB or plywood manufacturers. Some of these woodwastes are reground for nearby particleboard mills. However, other plywood companies that do not have the capacity to burn the waste must transport it to a location equipped to incinerate the waste or to a landfill. Because of high transportation costs, landfill costs, environmental concerns, and governmental regulations, alternative methods of disposal are being sought.
Phenolic-bonded softwood plywood is manufactured from southern yellow pine and Douglas-fir, and bonded with phenol-formaldehyde (PF) resin with...