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A Complete Closed-Loop CCA-Treated Wood Recycling System

A Complete Closed-Loop CCA-Treated Wood Recycling System. Chung-Yun Hse Southern Research Station USDA Forest Service Todd F. Shupe School of Renewable Natural Resources Louisiana State University R. C. Tang School of Forestry and wildlife Science Auburn University.

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A Complete Closed-Loop CCA-Treated Wood Recycling System

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  1. A Complete Closed-Loop CCA-Treated Wood Recycling System Chung-Yun Hse Southern Research Station USDA Forest Service Todd F. Shupe School of Renewable Natural Resources Louisiana State University R. C. Tang School of Forestry and wildlife Science Auburn University

  2. Residential use of CCA-Treated wood has resulted in substantial increasing consumption in recent years

  3. Year Volume of CCA-treated lumber (Million ft3) CCA consumed (Million punds) 1997 468 155 1990 359 147 1985 268 120 1980 90 36 1978 49 25 Table 1. Production trends in CCA-treated lumber in the United States. * *: Chemical Economics Handbook by SRI, Wood Preservatives, March 2000.

  4. Talking Points • Disposal problem • Recycling • Value-added products • Closed-loop recycling

  5. 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), and most of this was treated with CCA (Cooper 1993; Micklewright 1994).

  6. The Future • Cooper (1993) estimated that the future volumes of CCA-treated wood removed from service in the United States would rise from 1 million m3 in 1990 to 16 million m3 in 2020. • 300 metric tons of CCA-treated wood waste disposed in FL in 1996 … and will reach 2700 metric tons by 2016 (Solo-Gabriele and Townsend 1999)

  7. Present situation of treated wood recycling and CCA removal • Direct recycling for composite manufacturing • Incineration • Land-filling • Solvent extraction • Biological remediation • Closed-Loop Recycling System

  8. Closed loop recycling system Spent preservative-treated wood Reformation By products Liquefied wood Composite products (Poles & Panel Products) CCA-Free biomass materials Recovered CCA

  9. Experimental procedure Stirring (150-200oC, 60-120 min) CCA-wood PEG/glycerin acid Liquefied wood Mixing with acetone/water coagulant/precipitant (FeSO4/ Ca(OH)2) Filtration or centrifugation IPC analysis

  10. As As As Cｒ Cｒ Cｒ Cu Cu Cu Effect of FeSO4 content on the removal rates of CCA (Complexing insitu, Ca(OH)2, 5.94%)

  11. As As As Removalrate of CCA (%) Cr Cr Cr Cu Cu Cu FeSO4 (2.5%) FeCl2 (2.1%) H3PO4 (3.4%) Comparison of removal rates obtained from various complexing agents(Complexing in situ, Ca(OH)2, 5.94%)

  12. (3.96%) (7.92%) (3.56%) (5.94%) (1.98%) (2.77%) (0%) Effect of pH on the removal rates of CCA. (Complexing in situ, FeSO4, 2.5%)

  13. Conclusions and Remarks • Spent CCA-treated wood had a liquefaction reaction rate similar to the untreated wood • The amount of sulfuric acid has little effect on the removal rate • The presence of ferrous ions or phosphoric acid in the liquefaction enhances the removal of the heavy metal ions • The optimum FeSO4 dosage for maximum CCA removal is between 2.0 to 2.5% • The CCA removal rate increases substantially as the amount of Ca(OH)2 increased from 1.98% to 5.94% or as pH increased from 2.3 to 9.0. thereafter further increases in either Ca(OH)2 or pH yielded slightly lower CCA removal ratio. • On average, the Cu, Cr, and As were removed by 99.8%, 99.3%, and 98.9% respectively by this approach.

  14. Polyurethane Phenolic resin Recovered CCA CCA-recovering enhancing additives CCA-wood, liquefaction reagents A proposed recycling process for CCA treated wood Liquefaction reactor Aqueous solvent Coagulant precipitant Mixing tank Precipitation /separation apparatus CCA-free liquefied wood solution Sludge Sulfuric acid Recovery apparatus for CCA Recovery apparatus for liquefied wood Solvents (Acetone, MeOH)

  15. Spent Preservative-Treated Wood Reuse as solid wood products Thermochemical conversion Bio-remediation Energy conversion (creosote) Crossarm Liquefaction (CCA) Solvent extraction (steam, sub-and supercritical) Direct combustion Composite pole CCA free liquefied wood Wood based panel products Pyrolysis gasificantion Bio-degradable foam Bio-fuel, chemical Process residues (slabs and sawdusts) Adhesive (novolac, resol) Dechlorination Recovered CCA Landfill Preservative Closed-loop Preservative-Treated Wood Recycling System

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