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Composting
Formaldehyde
Resin Wood Wastes
 By Craig Coker,
Composting Specialist
NC
Div. Of Pollution Prevention & Environmental
Assistance
Demand for engineered wood products like
plywood, Medium Density Fiberboard (MDF), and Oriented Strand Board
(OSB) has been increasing at a steady rate, creating a wood waste
stream that may be suitable for use in composting as a carbon
source.
The main concern about composting these wood
wastes is the presence of formaldehyde from the urea-formaldehyde or
phenol-formaldehyde glues used in the manufacturing process of these
products. Two recent studies have examined the effect of composting
on formaldehyde in these wood wastes.
Wiltcher, et.al. conducted a six-month
composting study, in which 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 amended sawdust was composted for 180 days.
Compost samples were tested for weight loss
and for toxicity using the Microtox™ procedure. Greenhouse tests
were conducted on corn, soybeans and cotton by amending Bactomix
potting soil with 25% of each compost sample.
All treatments showed a significant decrease
in toxicity by day 180, maintained a neutral pH throughout the study
(with the exception of the horse manure treatment), and showed a
significant reduction in weight. The greenhouse tests were conducted
for 55 days.
Dry weights of row crop plants from the
greenhouse study showed no significant difference between potting
soil only and potting soil mixed with composted sawdust amended with
chicken manure. All other treatments were comparable with the
chicken manure, with the exception of the cotton gin trash
treatment.
The authors conclude that composting PF-bonded
sawdust can produce an acceptable soil amendment in a 180-day
period.
Leungprasert and Otten evaluated the
compostability of MDF sawdust in a simulated MSW. Composting was
conducted over a 10-day period at 45oC. and 55oC.
Simulated MSW was amended with 2.5% and 5.0% MDF sawdust by
weight.
Samples of the substrate were collected every
two days to determine the degradation rate of formaldehyde. Dry
matter loss over 10 days was less than 14% for the mesophilic phase
and 13% for the thermophilic phase. After 10 days, formaldehyde was
reduced over 90% in both mesophilic and thermophilic phases in
fixed-temperature conditions (at 2.5% MDF), by about 80% in
biodegradation tests (independent of temperature and MDF
concentration), and by about 66% under adiabatic conditions
(simulating outdoors composting). No gaseous formaldehyde emissions
were detected in either phase.
These two studies show that engineered wood
wastes may be suitable for use as a composting carbon source without
concern about formaldehyde resins and glues.
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