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CCA wood - Electrodialytic remediation of CCA-treated waste wood

LIFE00 ENV/DK/000369


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Contact details:

Project Manager: Arne VILLUMSEN
Tel: (45) 45 25 21 65
Fax: (45) 45 88 59 35
Email: av@byg.dtu.dk



Project description:

Background

The project addressed the problem of disposing of CCA (Chromate Copper arsenate) impregnated wood. CCA is to date the most widely used wood preservative worldwide, and the amount of treated wood is expected to increase in the years to come, both in Denmark and in the Community as a whole. The waste wood generated often still contains high concentrations of Chromium, Copper and Arsenic due to the strong fixation of CCA in the wood. Incineration of the waste wood is therefore not an option, and presently the only way of disposal is land filling. Electrodialytic remediation, using a low level current as a cleaning agent, is a possible method of removing Chromium, Copper and Arsenic from the wood. The method had been developed and patented by researchers at DTU, the Technical University of Denmark prior to the project, and had already proved to be efficient on the laboratory scale.


Objectives

The objective of the project was to design and build a pilot plant and to demonstrate that the method developed for the remediation of Chromate Copper arsenate (CCA) treated wood, which had been optimised to the maximum possible extent in the laboratory, was applicable at pilot plant scale. A further aim was to make estimates regarding the efficiency and competitiveness of the method at the industrial scale level.


Results

In this project a pilot plant for the electrodialytic remediation of CCA treated waste wood was developed and a series of remediation experiments were completed. The results obtained have shown that it is possible to remove CCA from treated wood chips on a larger scale than the laboratory one. On the basis of the experiences obtained with the pilot plant in this project, it is expected that the remediation process could be reproduced on an industrial scale. An important limiting factor for implementation of the remediation process in full scale is the time it takes for remediation. The present project has shown that at the given experimental conditions the remediation process is not finished even after several weeks. The remediation time must be shortened significantly if it is to be possible to treat all the incoming amounts of CCA impregnated waste wood. Test results demonstrate that Arsenic, which is the element of greatest environmental concern, has been removed almost completely from the wood (< 4 % ~ < 30 mg/kg left), and the concentration of copper and chromium has been reduced from 1300-1400 mg/kg to a few hundred mg/kg, corresponding to a removal efficiency of more than 80 % for chromium and almost 90 % for copper. The CCA containing process liquids have been evaluated for reuse as make-up water in the production of new wood preservatives. The results indicate that the liquids cannot be used directly, but probably are usable in a diluted form. Further investigation is necessary in this field. Even if the “target values” in the remediated wood (set at 1 mg/kg for copper and chromium and 0.25 mg/kg for arsenic) were never reached during the tests the beneficiary estimated that the remediated wood may be incinerated with no risk of arsenic release and the copper and chromium rich ashes may be reused as a secondary raw material in the metal refining industry. Presently only two commercially available options for handling of CCA treated waste wood are available throughout Europe: Incineration or disposal by land filling. The economic feasibility of the process seems promising, though it is dependent on the possibility to reuse all CCA containing process liquids and utilise the energy resources in the wood. Total treatment costs including investment costs amount to 210 Euro/tons, whereas total income generated (including saved costs for land-filling) amounts to 195 Euro/tons, the net cost for remediation thus corresponds to approx. 15 Euro/tons. It is estimated that approximately 1 kg of copper, chromium and arsenic respectively is removed per ton of wood remediated. In Denmark, the amount of CCA impregnated wood turning into waste is estimated to be 100.000 tons/year by 2010. If all this wood is treated by the electrodialytic method, more than 100 tons of copper, chromium and arsenic could potentially be recovered every year. CCA treated wood, and the problems of handling this kind of waste in an environmentally safe way, is not limited to Denmark. Treated wood has been and is still in use worldwide, and the quantities are expected to increase significantly in the years to come. The method demonstrated in this project will be equally useful in other geographic areas. The project has been presented at several conferences, workshops and seminars. Abstracts, full-papers and scientific articles have been produced and published at both national and international level. . A follow-up ex-post evaluation was carried out by the LIFE external monitoring team in July 2004. It showed that although the obtained results were ‘very promising’ regarding the possibilities of implementing the process in full-scale, unfortunately, due to lack of funding, there are no current projects continuing the work. However the results of this project continue to be disseminated through conference contributions and the publication of scientific articles. For example, an article entitled: “Electrodialytic Remediation of CCA-Treated Wood in a 2 Cubic Metre Pilot Plant” by I. V. Christensen et al., has been submitted to the Journal of Hazardous Materials.


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Environmental issues addressed:

Themes

Waste - Waste recycling
Industry-Production - Wood - Furniture
Waste - Hazardous waste


Keywords

cost-benefit analysis‚  heavy metal‚  waste treatment‚  wood‚  pollutant elimination‚  impregnating agent


Target EU Legislation

  • Waste
  • Directive 75/442/EEC -"Waste framework directive" (15.07.1975)
  • COM(1996)399 - Communication on an updated "Community strategy for waste management" (30.07.1996) ...
  • Directive 1999/31 - Landfill of waste (26.04.1999)

Natura 2000 sites

Not applicable


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Beneficiaries:

Coordinator Danmarks Tekniske Universitet, BYG.DTU, Environmental electrochemistry section
Type of organisation Research institution
Description The beneficiary is a technical research institution, which is part of the largest Danish technical University. DTU has a long record in applied research, and is nationally and internationally recognised.
Partners Faculdade de Ciencias e Tecnologia/UNL, Portugal Osmose Denmark as RGS90

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Project reference LIFE00 ENV/DK/000369
Duration 01-AUG-2001 to 01-JUL -2003
Total budget 281,610.00 €
EU contribution 136,988.00 €
Project location Københavns amt(Danmark) Lisboa e vale do Tejo(Portugal)

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Read more:

Project web site Internet site with link to laymans report in pdf file: Electrodialytic remediation of CCA-treated waste wood
Publication: Layman report Layman report

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Project description   Environmental issues   Beneficiaries   Administrative data   Read more   Print   PDF version