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Reclamation of Degraded Land with Biosolids

Reclamation of Degraded Land with Biosolids. Impacts of final land use, Impacts of reclamation method. GHG Consequences of Reclamation. F inal land use post-reclamation Reclamation improvements with biosolids Land- and biosolids use interact. Reclamation to forest.

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Reclamation of Degraded Land with Biosolids

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  1. Reclamation of Degraded Land with Biosolids Impacts of final land use, Impacts of reclamation method

  2. GHG Consequences of Reclamation • Final land use post-reclamation • Reclamation improvements with biosolids • Land- and biosolids use interact

  3. Reclamation to forest • High gains to Soil and Biomass C • Conventional and residuals reclamation

  4. Partial Reclamation + Development • Some soil/biomass C • But large GHG costs for construction and use over life cycle

  5. Field study – Soil C in Reclamation • Soil C benefits of biosolids reclamation • Compare similar conventional and biosolids sites up to 30 year post-reclamation

  6. Results: Soil C sequestration

  7. Results: Soil C sequestration • Soil C increases with biosolids • +15 Mg ha-1 (Centralia) • +38 Mg ha-1 (Highland Valley) • 0.11–1.14 Mg CO2e per Mg biosolids

  8. Results: Soil C sequestration • Increases and efficiency depend upon reclamation conditions and method Centralia, 0.11 Mg CO2e per tonne: Old sites, 1 m topsoil, very high biosolids rate Pennsylvania, 0.55 Mg CO2e per tonne: Old sites, relatively good topsoil, moderate biosolids addition Highland Valley, 1.03 Mg CO2e per tonne: No topsoil, very poor conventional recl., low biosolids rate Sechelt 1.14 Mg CO2e per tonne: Good response, poor topsoil moderate biosolids addition

  9. Study conclusions • 55–139 Mg CO2e ha-1 Soil C increase for using residuals • Increase was present even after 30 years • Specific changes related to site conditions and reclamation history • What about other GHG shifts with reclamation?

  10. Land use • House or forest? • Soil C • Biomass C • Construction/use/maintenance • Operations: transport, soil N2O, fertilizer credit, etc. • Competing biosolids uses

  11. Life cycle assessment of reclamation • What is LCA? • Track all inputs/outputs/activities required • Assign environmental impact • Assess (relative) environmental consequences

  12. Life cycle assessment of reclamation • Alternate post-reclamation land uses • Houses vs. forest • Reflects land-use pressures in Puget Sound

  13. Life cycle assessment of reclamation • 1 ha of degraded land • Urban margin of Puget Sound region, WA • 30 year timeline • Houses or forest

  14. Life cycle assessment of reclamation • “Choose your own adventure” • Natural cover (forest) • Biosolids reclamation • Conventional reclamation • Development

  15. Reclamation – Soil Carbon • Conventional Reclamation: 110 Mg CO2e • Biosolids reclamation: 220 Mg CO2e • Based on C accumulation rate and Mg CO2e per tonne of biosolids

  16. Reclamation – Biomass Carbon • PNW forests respond to biosolids (soil low in N) • Conventional: 183 Mg CO2e • Biosolids: 275 Mg CO2e

  17. Conventional Reclamation • Reclamation to Doug Fir forest • 110 Mg CO2e soil C • 183 Mg CO2e biomass C • 393 Mg CO2e per ha total

  18. Biosolids reclamation • Reclamation to D. Fir • 220 Mg CO2e soil C • 275 Mg CO2e biomass C • 18 Mg CO2e N applied as N2O • 477 Mg CO2e per ha total

  19. Biosolids reclamation  GHG emissions? • Need to consider emissions from biosolids management • Also alternate biosolids end-uses

  20. Biosolids to Agriculture • -220 Mg CO2e soil C • -275 Mg CO2e biomass C • +18 Mg CO2e N2O • +2 Mg CO2e transport (50 km) • Net: -475 Mg CO2e vs. • -140 Mg CO2e soil C • -28 Mg CO2e fertilizer credit • +11 Mg CO2e transport (300 km) • Net: -157 Mg CO2e

  21. Biosolids to Landfill • -220 Mg CO2e soil C • -275 Mg CO2e biomass C • +18 Mg CO2e N2O • +2 Mg CO2e transport (50 km) • Net: -475 Mg CO2e vs. • -29 Mg CO2e soil C • 346 Mg CO2e fugitive GHG • +14 Mg CO2e transport (350 km) • Net: +331 Mg CO2e

  22. Net GHG balance of restoring vegetation • Biosolids reclamation • -475 Mg CO2e (30 years, 1 ha, 100 dt biosolids) • Conventional reclamation • -293 Mg CO2e • What if development is chosen instead?

  23. Suburb development • Single-family houses • Asphalt roads • Built cover % according to USGS • Reclaim remaining land

  24. Suburb development: Housing • US Census population density • 3.9 houses/ha @ 243 m2 (~2,500 sq. ft) • LC GHG estimates: • Construction (incl. materials): 283 Mg CO2e • Maintenance/occupation: 989 Mg CO2e

  25. Suburb development: Roads • USGS % impervious cover • 0.44 ha ha-1 suburb • LC GHG estimates: • Construction (incl. materials): 93 Mg CO2e • Maintenance: 42 Mg CO2e

  26. Net GHG balance of Suburb Development • +1,272 Mg CO2e houses • +135 Mg CO2e roads • -52 Mg CO2e soil C • -86 Mg CO2e biomass C • Net: +1,269 Mg CO2e • Extra commuter traffic GHG? • Excluded from LCA but... • ca. +1,653 Mg CO2e over 30 yr

  27. Development or Reclamation? • Net: -293 to -475 Mg CO2e vs. • Net: +1,269 Mg CO2e • Modify and recombine scenarios to look for best and worst cases.

  28. Worst Case • Low density suburb, and... • Send biosolids to landfill, and... • Conventional reclamation of partial land • +1,600 Mg CO2e – largest emissions, lowest offsets +

  29. Optimized Case • Housing construction in urban core, and... • Biosolids for full reclamation • -5 to +141 Mg CO2e – minimized emissions, maximized offsets +

  30. Other ecosystem services • Improved with reclamation over development: • Water filtration; Biodiversity; Tourism value + + +

  31. Conclusions • Land-use after reclamation has the biggest impact • Biosolids end-use is also has an impact • and is determined in part by land-use choices • Biosolids in Puget Sound may have best end-use in reclamation • but first need to not develop (degraded) land

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