Supercritical Water Treatment of Supercritical Water Treatment of Creosote-Treated Wood WasteCreosote-Treated Wood Waste

Todd F. ShupeTodd F. Shupe

W. James CatalloW. James Catallo

IUFRO All Division 5 ConferenceIUFRO All Division 5 Conference29 October – 2 November, 200729 October – 2 November, 2007

Taipei, TaiwanTaipei, Taiwan

Main Research ObjectiveMain Research Objective

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

Recycling PotentialRecycling 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 PresentThe Present

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

Industrial ApplicationsIndustrial Applications

““Green” recyclingGreen” recycling Rural economic developmentRural economic development

Preservatives StudiedPreservatives Studied

Copper chromium arsenic (CCA)Copper chromium arsenic (CCA)

CreosoteCreosote Oil-borne pentachlorophenol (penta)Oil-borne pentachlorophenol (penta)

Supercritical WaterSupercritical Water

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

Supercritical WaterSupercritical Water

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

Creosote MethodsCreosote Methods

1mm particle size1mm particle size pH 10pH 10 400 400 10 10 ooC/280 bar for 15 hrs. including C/280 bar for 15 hrs. including

heat up and cool downheat up and cool down

Fresh CreosoteFresh Creosote

Weathered CreosoteWeathered Creosote

After 12 h SC TreatmentAfter 12 h SC Treatment

Fresh Creosote Weathered Creosote

“Regenerated” Creosote

After 12 h SC Treatment

Creosote ResultsCreosote Results

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

Creosote ResultsCreosote Results

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

Creosote ResultsCreosote Results

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

ConclusionsConclusions

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

Current ResearchCurrent Research

Detoxification of mixed treated wood types Detoxification of mixed treated wood types (no sorting of different preservatives)(no sorting of different preservatives)

KineticsKinetics Gas phase analysisGas phase analysis Efficacy testing of “recycled” creosoteEfficacy testing of “recycled” creosote

School of Renewable Natural ResourcesLouisiana State UniversityRm. 111 Renewable Natural Resources Bldg.Baton Rouge, LA 70803-6202

phone: (225) 578-6432fax: (225) 578-4251

http: http://www.rnr.lsu.edu/e-mail: tshupe@lsu.edu

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