An environmental comparison between powdered activated carbon and biochar
for tertiary wastewater treatment Kyle ThompsonPh.D. CandidateUniversity of Colorado BoulderEnvironmental Engineering
Co-Authors: Dr. Sherri Cook, Josh Kearns, Dr. Detlef Knappe, Kyle Shimabuku, Dr. Scott Summers
USBI 2016Oregon State UniversityAug. 24th, 2016
Acknowledgements
2
• National Science Foundation
• Jonah Levine of Biochar Solutions, Inc. and Confluence Energy, LLC
• Cole Sigmon of City of Boulder
• Dr. Sherri Cook & Dr. Scott Summers Lab Groups
Organic micropollutants from wastewater are a pervasive threat to the aquatic environment.
3Meador et al. Environmental
Pollution, 2016, 213 (C).
Triclosan
Estrone
Nonylphenol
Powdered activated carbon (PAC) is a relatively sustainable treatment method for organic micropollutants.
4
Tansel and Nagarajan. Advances in Environmental Research, 2004, 8 (3-4).
Powdered activated carbon (PAC) is a relatively sustainable treatment method for organic micropollutants.
5Plakas et al. Water Science & Technology, 2016, 73 (7).
0
50
100
Ozone + UV PhotocatalyticMembrane
Reactor
Microfiltration +ReverseOsmosis
PAC +Ultrafiltration
Com
posit
e In
dex
Economic Environmental Social
MoreSustainable
Less Sustainable
Biochar can have a net environmental benefit due to renewable energy production and carbon sequestration.
6
Purevsuren and Avid. Journal of Materials Science, 2003, 38 (11).
Biochar can have a net environmental benefit due to renewable energy production and carbon sequestration.
7
PAC + Ultrafiltration
Ibarrola et al. Waste Management, 2012, 32 (5).
Net
car
bon
abat
emen
t (to
nnes
of C
O2
eq. t
-1)
Sulfamethoxazole (SMX) is one of the most challenging organic micropollutants to remove by adsorption.
8Westerhoff et al. Environmental Science & Technology, 2005, 39 (17).
Percentage Removal with 5 mg/L PAC
0% 25% 50% 75%
This comparative life cycle assessment used TRACI to express environmental impacts in 10 midpoint categories.
9
classify & characterize
categories
respiratory effects (kg PM2.5 eq)global warming (kg CO2 eq)smog (kg O3 eq)ozone depletion (kg CFC-11 eq)acidification (kg SO2 eq)carcinogenics (CTUh)non-carcinogenics (CTUh)ecotoxicity (CTUe)eutrophication (kg N eq)fossil fuel depletion (MJ surplus)
Life Cycle Impact Assessment
Life Cycle Impacts
airemissions
wateremissions
soil emissions
Life CycleInventory
raw materials
energy
unit process #1
unit process #2
unit process #3
unit process #4
unit process #5
Life Cycle Stages
goal definition & scoping
inventory
impact
interpretation
75% Removal of SMX from 12.5 MGD of wastewater
The first step of an LCA is goal definition and scoping.
System Boundary
adsorbent dosing and removal
hauling landfill
land application site
receiving water
coal (unmined) PAC generation storagehauling
landfill
land application site
receiving water
trees(forest)
wood chip generation storagehauling
2˚ effluent
landfill
land application site
receiving water
storagebiosolids drying & pyrolysis
artificial fertilizer production
coal or trees PAC or wood biochar generation hauling
biosolids
2˚ effluent
biosolids
2˚ effluent
biosolids
PAC
Use
Woo
d B
ioch
ar U
seB
ioso
lids
Bio
char
Use
Key
Out of Scope(raw material
creation)
Out of Scope(impacts at destination)WW effluent
wood chip drying & pyrolysis
energy positive
adsorbent dosing and removal
hauling
adsorbent dosing and removal
hauling
material flow
Three adsorbents: PAC, wood biochar, biosolids biochar
70 mg/L
150 mg/L
150 mg/L
Shimabuku et al. Water Research, 2016, 96 (C).
-4
-3
-2
-1
0
1
2
Eutrophication(kgN eq)
Carcinogenics(CTUh)
Ecotoxicity(CTUe)
Acidification(kgSO2 eq)
Ozonedepletion
(kgCFC-11 eq)
Fossil fueldepletion (MJ
surplus)
Smog (kgO3eq)
Globalwarming
(kgCO2 eq)
Respiratoryeffects
(kgPM2.5 eq)
Noncarcinogenics
(CTUh)
Emis
sion
Fac
tors
(rel
ativ
e to
PAC
)
Wood Biochar
Results are normalized to PAC.
Eutroph. Carcinogenics Fossil FuelDepletion
SmogEcotoxicity Global Warming
Respiratory Effects
Non Carcinogenics
Acidification Ozone Depletion
11
PAC
25th-75th Percentile
Wood biochar has lower environmental impacts than PAC in 8/10 categories.
-4
-3
-2
-1
0
1
2
3
Eutrophication(kgN eq)
Carcinogenics(CTUh)
Ecotoxicity(CTUe)
Acidification(kgSO2 eq)
Ozonedepletion
(kgCFC-11 eq)
Fossil fueldepletion (MJ
surplus)
Smog (kgO3eq)
Globalwarming
(kgCO2 eq)
Respiratoryeffects
(kgPM2.5 eq)
Noncarcinogenics
(CTUh)
Emis
sion
Fac
tors
(rel
ativ
e to
PAC
)
Wood Biochar Biosolids Biochar with Wood Biochar
Biosolids biochar is worse than wood biochar in all environmental impact categories.
12
PAC
Carcinogenics Fossil FuelDepletion
SmogEcotoxicity Global Warming
Respiratory Effects
Non Carcinogenics
Acidification Ozone Depletion
Eutroph.
25th-75th Percentile
-1.5
-1
-0.5
0
0.5
1
1.5
PAC Wood Biochar Biosolids Biochar + WoodBiochar
Smog
(rel
ativ
e to
PAC
) Adsorbent DisposalAdsorbent StorageHauling (Adsorbent Delivery)Artificial Fertilizer ProductionBiochar Net Energy GenerationBiosolids Biochar GenerationPrimary Adsorbent Generation
Net Environmental Impact
Wood biochar had higher impacts from adsorbent storage and adsorbent disposal.
Net Environmental Impact
-1.5
-1
-0.5
0
0.5
1
1.5
PAC Wood Biochar Biosolids Biochar + WoodBiochar
Smog
(rel
ativ
e to
PAC
) Adsorbent DisposalAdsorbent StorageHauling (Adsorbent Delivery)Artificial Fertilizer ProductionBiochar Net Energy GenerationBiosolids Biochar GenerationPrimary Adsorbent Generation
Wood biochar had less impact from delivery and an environmental benefit from pyrolysis energy.
-1.5
-1
-0.5
0
0.5
1
1.5
PAC Wood Biochar Biosolids Biochar + WoodBiochar
Smog
(rel
ativ
e to
PAC
) Adsorbent DisposalAdsorbent StorageHauling (Adsorbent Delivery)Artificial Fertilizer ProductionBiochar Net Energy GenerationBiosolids Biochar GenerationPrimary Adsorbent Generation
Net Environmental Impact
Biosolids biochar had more impact than wood biocharbecause its generation is energy consuming.
Eutroph. Carcinogenics
Emis
sion
Fac
tors
(rel
ativ
e to
Cal
iforn
ia P
AC)
-10Acidification Ozone
DepletionFossil FuelDepletion
Smog Global Warming
Respiratory Non Carcinogenics
Ecotoxicity
0
-5
5
10
Kentucky PAC (70 mg/L)
California PAC (70 mg/L)
Wood biochar (600 mg/L)
Wood biochar (150 mg/L)
The relative sustainability of wood biochar depends on its adsorption capacity.
17
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
wastewater treatment plants withorganic matter and nutrient removal
(n=6)*
Wood Biochar 75% SMX Removal -Carbon Mitigation
Glo
bal W
arm
ing
(kg
CO2
eq./
m^3
was
tew
ater
)
Wood biochar usage is sufficient to offset the global warming impact of an entire wastewater treatment plant.
*Rodriguez-Garcia et al. Water Research, 2011, 45 (16).
Standard Deviation
Wood biochar has lower environmental impacts than PAC or biosolids biochar.
Relative sustainability of wood biochar depends on adsorption capacity.
The environmental benefit of wood biochar is largely due energy production during pyrolysis.
Conclusions