Supercritical Water Treatment of Creosote-Treated Wood Waste Todd F. Shupe W. James Catallo IUFRO All Division 5 Conference 29 October – 2 November, 2007 Taipei, Taiwan

Main Research Objective



To develop a complete closed-loop recycling system to achieve zero discharge of wood preservatives into the waste stream. The system must be economically viable and environmentally

friendly.

Recycling Potential •There is a need for extensive research into ways of reducing, reusing, recycling, and disposing of treated wood in environmentally acceptable ways (Cooper 1994).

The Present  It has been estimated that about 5 million tons of spent preservative treated wood is disposed of annually into landfills in the United States (Falk 1997).

Industrial Applications  “Green” recycling  Rural economic development

Preservatives Studied  Copper chromium arsenic (CCA) 

Creosote

 Oil-borne pentachlorophenol (penta)

Supercritical Water  Supercritical (SC) water (>374 o C/221 bar) under anoxic and reducing conditions has been used for a variety of synthetic chemical transformation/recycling purposes.

Supercritical Water  The SC phase is one of the most energetic and chemically dynamic conditions known for aqueous systems, including a) liquid water under conditions normally observed, b) very high pressures and, c) superheated steam.

Creosote Methods  1mm particle size   pH 10 400  10 o C/280 bar for 15 hrs. including heat up and cool down

Fresh Creosote

Weathered Creosote

After 12 h SC Treatment

Fresh Creosote Weathered Creosote “Regenerated” Creosote After 12 h SC Treatment

Creosote Results  During treatment, the creosote-derived hydrocarbon residues in the wood were nearly completely (>99%) recovered and the wood itself was transformed into a mixture of hydrocarbons including substituted benzenes, phenolics and light PAHs.

Creosote Results  These wood-derived transformation products served to reconstitute the "light end" of the creosote, which largely had been lost while in service.

Creosote Results  Thus, the hazardous waste (creosote hydrocarbon mixture) was recovered, and the solid waste (wood) was transformed into a complimentary product mixture in a single pass. Solid residues after 12-20 h of treatment were <2% w/w.

Conclusions  Creosote - The hazardous waste (creosote hydrocarbon mixture) was recovered, and the solid waste (wood) was transformed into a complimentary product mixture in a single pass forming a “recycled” creosote.

Current Research  Detoxification of mixed treated wood types (no sorting of different preservatives)  Kinetics  Gas phase analysis  Efficacy testing of “recycled” creosote

Contact Us

School of Renewable Natural Resources Louisiana State University Rm. 111 Renewable Natural Resources Bldg.

Baton Rouge, LA 70803-6202 phone: (225) 578-6432 fax: (225) 578-4251 http: http://www.rnr.lsu.edu/ e-mail: [email protected]

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