Reclamation of Degraded Land
with Biosolids
Impacts of final land use,
Impacts of reclamation method
GHG Consequences of Reclamation
• Final land use post-reclamation
• Reclamation improvements with biosolids
• Land- and biosolids use interact
Reclamation to forest
• High gains to Soil and Biomass C
• Conventional and residuals reclamation
Partial Reclamation + Development
• Some soil/biomass C
• But large GHG costs for construction and use
over life cycle
Field study – Soil C in Reclamation
• Soil C benefits of biosolids reclamation
• Compare similar conventional and biosolids
sites up to 30 year post-reclamation
Location
Centralia, WA
Sechelt, BC
Highland Valley, BC
RMI, Mass. & NH
Pennsylvania
Mine type
Coal
Sand & Gravel
Copper/Moly
Sand & Gravel
Coal
Sample N
35
25
20
9
28
Max Age
17
9
8
7
27
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
Mg C per Mg biosolids, 0–15 cm
Results: Soil C sequestration
C storage efficiency
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0.2
0.1
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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
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?
Land use
• House or forest?





Soil C
Biomass C
Construction/use/maintenance
Operations: transport, soil N2O, fertilizer credit, etc.
Competing biosolids uses
Life cycle assessment of reclamation
• What is LCA?
 Track all
inputs/outputs/activi
ties required
 Assign environmental
impact
 Assess (relative)
environmental
consequences
Life cycle assessment of reclamation
• Alternate post-reclamation land uses
 Houses vs. forest
 Reflects land-use pressures in Puget Sound
Life cycle assessment of reclamation
•
•
•
•
1 ha of degraded land
Urban margin of Puget Sound region, WA
30 year timeline
Houses or forest
Life cycle assessment of reclamation
• “Choose your own adventure”
• Natural cover (forest)
 Biosolids reclamation
 Conventional reclamation
• Development
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
Reclamation – Biomass Carbon
• PNW forests respond to
biosolids (soil low in N)
• Conventional: 183 Mg CO2e
• Biosolids: 275 Mg CO2e
Conventional Reclamation
• Reclamation to Doug Fir
forest
• 110 Mg CO2e soil C
• 183 Mg CO2e biomass C
• 393 Mg CO2e per ha total
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
Biosolids reclamation 
GHG emissions?
• Need to consider emissions from
biosolids management
• Also alternate biosolids end-uses
Biosolids to Agriculture
vs.
•
•
•
•
-220 Mg CO2e soil C
-275 Mg CO2e biomass C
+18 Mg CO2e N2O
+2 Mg CO2e transport
(50 km)
• Net: -475 Mg CO2e
• -140 Mg CO2e soil C
• -28 Mg CO2e fertilizer
credit
• +11 Mg CO2e transport
(300 km)
• Net: -157 Mg CO2e
Biosolids to Landfill
vs.
•
•
•
•
-220 Mg CO2e soil C
-275 Mg CO2e biomass C
+18 Mg CO2e N2O
+2 Mg CO2e transport
(50 km)
• Net: -475 Mg CO2e
• -29 Mg CO2e soil C
• 346 Mg CO2e fugitive
GHG
• +14 Mg CO2e transport
(350 km)
• Net: +331 Mg CO2e
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?
Suburb development
• Single-family houses
• Asphalt roads
• Built cover % according
to USGS
• Reclaim remaining land
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/occupatio
n: 989 Mg CO2e
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
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
Development or Reclamation?
vs.
• Net: -293 to -475
Mg CO2e
• Net: +1,269 Mg
CO2e
• Modify and recombine scenarios to look for
best and worst cases.
Worst Case
+
•
•
•
•
Low density suburb, and...
Send biosolids to landfill, and...
Conventional reclamation of partial land
+1,600 Mg CO2e – largest emissions, lowest offsets
Optimized Case
+
• Housing construction in urban core, and...
• Biosolids for full reclamation
• -5 to +141 Mg CO2e – minimized emissions,
maximized offsets
Other ecosystem services
• Improved with reclamation over development:
 Water filtration; Biodiversity; Tourism value
+
+
+
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 enduse in reclamation
 but first need to not develop (degraded) land