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