Alternatives

 

 

Chemical Alternatives

There are several alternative chemicals being promoted as alternatives to CCA, as listed in the table below. None of the available alternatives is a complete substitute on its own for all the uses of CCA and, although they do not involve arsenic or chrome, they still pose environmental and health risks.

Description of Chemical Alternatives to CCA

ACQ
CBA
CDDC
CC
LOSP
Full name
Alkaline copper quaternary
Copper boron azole
Copper dimethyl-dithiocarbamate
Copper citrate
Liquid Organic Solvent Preservative, including tri-butyl-tin (TBT) and permethrin
Delivery of treatment
Water-based solution
Water-based solution
Water-based solution
Water-based solution
Hydrocarbon solven
Applications
For all except marine immersion
For all except marine immersion and freshwater
For above ground applications only
Impact of copper
More leaching than CCA- thus higher aquatic toxicity
More leaching than CCA- thus higher aquatic toxicity
Less leaching than CCA (likely due to being more strongly ‘fixed’)
More leaching than CCA- thus higher aquatic toxicity
Corrosivity
More corrosive to brass and bronze than CCA
Same as CCA
Same as CCA
More corrosive to brass and bronze than CCA
Other risks
Leached most boron
Leached most boron
Hydrocarbon solvents risky as air and storm-water pollution at treatment plants; volatile organic compounds make it difficult to work with
Benefits
No leaching of As or Cr; Lower mammalian toxicity than CCA
No leaching of As or Cr; Lower mammalian toxicity than CCA
No leaching of As or Cr; Lower mammalian toxicity than CCA
No leaching of As or Cr; Lower mammalian toxicity than CCA
Cost
10-30% higher than CCA3
10-30% higher than CCA3
Higher than CCA

Sources: Townsend et al, 2003; Solo-Gabriele et al, 2000; Lebow, 2004; NSW EPA, 2003c.

In addition, many of the alternatives listed in the table cost between 8 and 15 percent more than CCA-treated timber, although it is anticipated that costs will fall if demand rises because of limitations to the use of CCA (NSW EPA, 2003b).

These alternative chemicals employ copper as the main biocide, but also include co-biocides mainly to prevent copper-tolerant fungal decay (Lebow, 2004b). In their evaluation of alternative chemicals, Solo-Gabriele et al (2000) noted that ‘viable non-arsenical waterborne alternatives are available for above ground and ground contact applications’, which accounts for 60% of the treated wood volume. However, little is known of the impact of the co-biocides, and they recommend that their environmental impacts be further evaluated before they are promoted. Townsend et al (2003a) also warn against complete changeover to these chemicals, recommending chemical alternatives to CCA for all situations except those that might ‘impact sensitive aquatic ecosystems’, especially those with limited flushing (Townsend et al, 2003a).

Finally, if CCA-treated timber is to remain in place, the leaching and dislodgement impacts can be reduced temporarily by coating with a stain. Research by Strömberg (2003) found that acrylic coatings and stains provided the longest protection. She also determined that the manual application and drying of this stain was the most important phase in terms of minimizing the resultant environmental impacts. Lebow et al (2003) also determined that paint or pigmented stains provided an effective short term barrier to prevent CCA leaching from the treated timber, noting that clear stains or not sealing the timber quintupled the rate of leaching due to ultra-violet exposure.

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References:

Lebow, S., Williams, R. and Lebow, P. (2003), ‘Effect Of Simulated Rainfall And Weathering On Release Of Preservative Elements From CCA Treated Wood’. Environmental Science & Technology 38 (Sept. 15): 4077-4082.

Lebow, S. (2004b), ‘Alternatives to Chromated Copper Arsenate (CCA) for Residential Construction’, Environmental Impacts Of Preservative-Treated Wood Conference, February 8-11, 2004, Orlando, Florida.

NSW EPA (2003b), Environmental Compliance Report- Wood Preservation Industry: Part B: Review of Best Practice and Regulation, NSW Environment Protection Authority, June)

NSW EPA (2003c), ‘Questions and answers on the wood preservation industry’, NSW Environmental Protection Authority website, http://www.environment.nsw.gov.au/licensing/qaswood.htm (accessed 1/11/04).

Solo-Gabriele, H., Kormienko, M., Gary, K., Townsend, T., Tolaymat, T. (2000), Alternative Chemicals and Improved Disposal-End Management Practices for CCA-treated Wood, Florida Center For Solid And Hazardous Waste Management, Florida.

Strömberg, L. (2003), ‘Minimisation Of The Environmental Impacts Of Coatings On Exterior Wood By Optimisation Of Their Life Spans’, International Research Group On Wood Preservation 34, Brisbane, May.

Townsend, T., Stook, K., Ward, M., Solo-Gabrielle, H. (2003) ‘Leaching And Toxicity Of CCA-Treated And Alternative-Treated Wood Products’, Florida Center For Solid And Hazardous Waste Management, Report #02-4

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Introduction | Chemical Alternatives | Physical Alternatives | Industry Response