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. 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). 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 “Green” recycling Rural economic development Rural economic development

Preservatives Studied Copper chromium arsenic (CCA) Copper chromium arsenic (CCA) Creosote Creosote Oil-borne pentachlorophenol (penta) 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 (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. 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 1mm particle size pH 10 pH  10 o C/280 bar for 15 hrs. including heat up and cool down 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 CreosoteWeathered 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. 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. 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 h of treatment were <2% w/w. 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 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. 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) Detoxification of mixed treated wood types (no sorting of different preservatives) Kinetics Kinetics Gas phase analysis Gas phase analysis Efficacy testing of “recycled” creosote Efficacy testing of “recycled” creosote

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