Effect of vegetable compost on leaching of CCA components from treated wood - An Update

IRG/WP 95-50048

P A Cooper, Y T Ung

In an earlier study, the effect of compost on CCA-C leaching was compared with leaching losses under different exposure conditions. Small treated cubes (25 mm³) were destructively sampled over a 12 month period and the residual CCA determined for exposure to compost in a compost bin, exposed to natural rain and buried in soil. This study provides a comparison after 3 years of samples exposed to compost and to natural weathering and summarizes CCA leaching losses from a treated wood compost bin after 12 months use. On the basis of small treated cubes (25 mm³) significant losses of all CCA components has occurred after 3 years exposure to compost. Copper has the most significant losses. After three years, blocks exposed to compost were extensively degraded by soft rot and other fungi, probably as a result of the high copper losses. The losses from the actual compost bin are highly variable and not statistically significant. As observed with the blocks, copper was preferentially extracted. There was an increased level of all contaminants in the compost, mainly concentrated in the 0-25 mm zone adjacent to the treated wood panels. Considering the increased rate of depletion of CCA components and the more rapid biological degradation of wood exposed to compost, we do not recommend the use of CCA treated wood for this purpose.


Conference: 95-05-11/16 Helsingør; Denmark

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