environmental sustainability assessment of a microalgae ... · heat soil conditioner 2 mab-flocs...
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Environmental Sustainability Assessment of a Microalgae
Raceway Pond Treating Wastewater from a Recirculating
Aquaculture System
From Upscaling to System Integration
Sophie Sfez(a), Sofie Van Den Hende(b), Sue Ellen Taelman(a), Steven De
4th International Congress on Sustainability Science & Engineering
26-29 May 2015
Sustainable Pathways for Algal Bioenergy Sustainable Pathways for Algal Bioenergy
Sophie Sfez(a), Sofie Van Den Hende(b), Sue Ellen Taelman(a), Steven De
Meester(a), Jo Dewulf(a)
(a) Department of Sustainable Organic Chemistry and Technology, Ghent University, Coupure Links 653, B-
9000 Ghent, Belgium
(b) Laboratory for Industrial Water and Eco-Technology (LIWET), Faculty of Bioscience Engineering, Ghent
University, Graaf Karel de Goedelaan 5, B-8500 Kortrijk, Belgium
Introduction
EnAlgae: INTERREG IVB North West Strategic Initiative (03/2011 – 06/2015)
9 pilot scale algae cultivation sites (micro- and macroalgae)
Sustainable Pathways for Algal Bioenergy
• In Roeselare, Belgium: Algae-based wastewater treatment plant, treating wastewater from a pikeperch recirculating aquaculture systems (RAS)
Aquaculture: fast growing sector competing for freshwater resources
RASs: promising option to mitigate the environmental footprint of aquaculture systems
Introduction
Settling tank
Backwash
Backwash supernatant
Biofilters
UVO2
Recirculating aquaculture systemAlgae-based wastewater treatment
system
Sustainable Pathways for Algal Bioenergy
tank
Fish sludge
wastewater
Fish ponds Drum filters
Biofilters
Water
Anaerobic digestion
The MaB-floc technology tested in 2013 in Belgium at pilot scale to treat pikeperch aquaculture wastewater from the Aquaculture Research Center of Inagro (Belgium)
As they grow, MaB-flocs need to be harvested, delivering a new source of biomass: valorisation as shrimp feed and anaerobic digestion were tested at pilot scale
MaB-flocs: bioflocculating consortium of bacteria and microalgae
Introduction
� Industry needs insights to know which direction to take
Sustainable Pathways for Algal Bioenergy
Goal of the studyGoal 1: Assess the environmental footprint of a pilot MaB-floc SBR treating
pikeperch culture WW and identify its improvement potential
Goal 2: Forecast the most sustainable valorisation pathway for MaB-flocs in the framework of an integrated aquaculture waste treatment system at industrial scale
Pilot MaB-floc SBR treating pikeperch wastewater (real case)
Studied MaB-floc based WWT plants
MaB-floc
liquor
Backwash
supernatant
Electricity
Supernatant
Flue
gasLandSunlightNatural
gas
Heat
MaB-floc
raceway pond
To
stir
rin
g p
um
ps
Settling
tank
Electricity
1 pondArea: 12 m2
Volume: 28 m3
Flow: 2.59 m3 day-1
Sustainable Pathways for Algal Bioenergy
Effluent
water
MaB-floc
liquor
Van Den Hende 2014
Pilot MaB-floc SBR treating pikeperch wastewater (real case)
Hypothetical up-scaled cases (1000 m3 of WW treated per day):
L: linearly up-scaled MaB-floc plant
Studied MaB-floc based WWT plants
41 pondsArea: 245 m2 pond-1
Volume: 98 m3 pond-1
Flow: 24.5 m3 day-1 pond-1
50 m
5 m
Electricity
Flue gas
Sunlight
Natural gasHeat
Supernatant
MaB-floc
raceway
pond
To stirring
pumps
Blower
Sustainable Pathways for Algal Bioenergy
Flow: 24.5 m3 day-1 pond-1
41 reactors =
1ha of cultivation
Effluent
WaterLand
Sunlight
Settling
tank
Electricity
MaB-floc
liquor
Pilot MaB-floc SBR treating pikeperch wastewater (real case)
Hypothetical up-scaled cases (1000 m3 of WW treated per day):
L: linearly up-scaled MaB-floc plant
S: linearly up-scaled MaB-floc plant with improved stirring system
Studied MaB-floc based WWT plants
Sustainable Pathways for Algal Bioenergy
Propeller pump22 W m-2
Paddle wheel 5.1 W m-2
Pilot MaB-floc SBR treating pikeperch wastewater (real case)
Hypothetical up-scaled cases (1000 m3 of WW treated per day):
L: linearly up-scaled MaB-floc plant
S: linearly up-scaled MaB-floc plant with improved stirring system
E: linearly up-scaled MaB-floc plant with Belgian electricity mix replaced by 100% wind energy
Studied MaB-floc based WWT plants
Sustainable Pathways for Algal Bioenergy
Pilot MaB-floc SBR treating pikeperch wastewater (real case)
Hypothetical up-scaled cases (1000 m3 of WW treated per day):
L: linearly up-scaled MaB-floc plant
S: linearly up-scaled MaB-floc plant with improved stirring system
E: linearly up-scaled MaB-floc plant with Belgian electricity mix replaced by 100% wind energy
M: linearly up-scaled MaB-floc plant with MaB-floc productivity
Studied MaB-floc based WWT plants
Sustainable Pathways for Algal Bioenergy
M: linearly up-scaled MaB-floc plant with MaB-floc productivity improved by 30%
Valorisation of MaB-flocs as shrimp feed
Studied integrated system
Backwash
wastewater
Heat
Treated backwash supernatant released in the sewage system
DigestateElectricity
Heat
Valorisation as shrimp feed
Fish sludgeDigester
Maize silage
Shrimp feed
Drying
Soil conditioner
Raceway ponds
MaB-floc liquor Dewatering
CHPBiogas Electricity to the grid
Pikeperch RAS Settling Milling
Three scenarios are compared:
Sustainable Pathways for Algal Bioenergy
Soil conditioner
Valorisation as biogas
Soil conditioner
MaB-floc liquor
Backwash
wastewater
Heat
Treated backwash supernatant released in the sewage system
Fish sludge
Maize silage
Digester Biogas
DigestateRaceway
ponds Dewatering
CHPElectricityto the grid
Pikeperch RAS Settling
Valorisation of MaB-flocs as biogas
Three scenarios are compared:Valorisation of MaB-flocs as shrimp feed
Valorisation of MaB-flocs as biogas
Baseline scenario
Studied integrated system
Backwash
wastewater
Backwash supernatant released in the sewage system
Electricity
HeatPikeperch
RAS
Fish sludge
Settling
Maize silageBiogas
Electricity to the grid
Digester CHP
Sustainable Pathways for Algal Bioenergy
DigestateElectricityMaize silage
Soil conditionerHeat
2 MaB-flocs plants are integrated:� Plant L (linearly up-scaled plant)
� Plant SEM (plant L with the 3 improvements implemented
50 m
5 m
41 reactors =
1ha of cultivation
Electricity
Effluent
Water
Flue gas
Land
Sunlight
Natural gasHeat
Settling
tank
Electricity
Supernatant
MaB-floc
raceway
pond
To stirring
pumps
MaB-floc
liquor
Blower
50 m
5 m
41 reactors =
1ha of cultivation
Electricity
Effluent
Water
Flue gas
Land
Sunlight
Natural gasHeat
Settling
tank
Electricity
Supernatant
MaB-floc
raceway
pond
To stirring
pumps
MaB-floc
liquor
Blower
+ + +
Env. Sustainability Analysis
Functional unit
Life Cycle Assessment (LCA), ISO standards 14040 & 14044
Goal and scope
definition
Inte
rpre
tati
on
Goal 1: comparison of the 4 MaB-floc
based WWTP
Goal 2: SA of the integration of MaB-floc based WWTP in
an aquaculture system
Production of 1 kg TSS MaB-floc liquor
Treatment of 1 m3
of wastewater
Syst. boundaries Cradle-to-gate
Sustainable Pathways for Algal Bioenergy
Inventory
analysis
Impact
assessment
Inte
rpre
tati
on
Foreground system
Pilot: site dataUp-scaled: pilot data + literature
Data from up-scaled plant + ecoinvent v 2.2 + literature
Background system
ecoinvent v 2.2 + literature
Resource consumption (CEENE 2013) � resource efficiency analysis
Global warming potential (IPCC 2007) � air emission efficiency analysis
Marine and freshwater eutrophication (ReCiPe 2013) � water emission efficiency analysis
LCA results: environmental sustainability of the MaB-floc based WWTP
Resource footprint (CEENE results)
50
100
150
200
250
300
350
400
450
ex
,CEEN
Ek
g-1
Ma
B-f
loc T
SS
Total CEENE: 848 MJ kg-1 MaB-floc TSS
Sustainable Pathways for Algal Bioenergy
0
50
P L S E M P L S E M P L S E M P L S E M P L S E M P L S E M P L S E M
Land resource Fossil fuels Metal ores Minerals Nuclear energy Water resources Abiotic renewable
resources
MJ e
x,C
EEN
E
Pil
ot S M
Electricity consumption - stirring pumps Electricity consumption - other pumps
Electricity consumption - flue gas blower Heating of the pond
Direct Land occupation Infrastructure
Direct phosphorus emissions to water Direct nitrogen emissions to water
LCA results: environmental sustainability of the MaB-floc based WWTP
Resource footprint (CEENE results)
50
100
150
200
250
300
350
400
450
ex
,CEEN
Ek
g-1
Ma
B-f
loc T
SS
50
100
150
200
250
300
350
400
450
ex,C
EEN
Ek
g-1
Ma
B-f
loc
TS
S
-69%
-77%
Total CEENE plant L: 278 MJ kg-1 MaB-floc TSS
Sustainable Pathways for Algal Bioenergy
0
50
P L S E M P L S E M P L S E M P L S E M P L S E M P L S E M P L S E M
Land resource Fossil fuels Metal ores Minerals Nuclear energy Water resources Abiotic renewable
resources
MJ e
x,C
EEN
E
0
50
P L S E M P L S E M P L S E M P L S E M P L S E M P L S E M P L S E M
Land resource Fossil fuels Metal ores Minerals Nuclear energy Water resources Abiotic renewable
resources
MJ e
x,C
EEN
E
Pil
ot S M
Electricity consumption - stirring pumps Electricity consumption - other pumps
Electricity consumption - flue gas blower Heating of the pond
Direct Land occupation Infrastructure
Direct phosphorus emissions to water Direct nitrogen emissions to water
LCA results: environmental sustainability of the MaB-floc based WWTP
IPCC 2007 - Climate changeRe CiPe 2013 - Marine
eutrophication
Re CiPe 2013 - Freshwater
eutrophication
4,E-03
6,E-03
8,E-03
1,E-02
1,E-02
1,E-02
kg
-1M
aB
-flo
c T
SS
4,E-03
6,E-03
8,E-03
1,E-02
1,E-02
1,E-02
2,E-02
-1 M
aB
-flo
c T
SS
10
15
20
25
30
eq
kg
-1M
aB
-flo
c T
SS
4,E-03
6,E-03
8,E-03
1,E-02
1,E-02
1,E-02
kg
-1M
aB
-flo
c T
SS
4,E-03
6,E-03
8,E-03
1,E-02
1,E-02
1,E-02
2,E-02
-1 M
aB
-flo
c T
SS
10
15
20
25
30
eq
kg
-1M
aB
-flo
c T
SS
67% 85% 91% 28% 34% 36% 67% 90% 97% 75%
Sustainable Pathways for Algal Bioenergy
Pil
ot S M
Electricity consumption - stirring pumps Electricity consumption - other pumps
Electricity consumption - flue gas blower Heating of the pond
Direct Land occupation Infrastructure
Direct phosphorus emissions to water Direct nitrogen emissions to water
0,E+00
2,E-03
4,E-03
Pilot L S E
kg
Pe
qk
g
0,E+00
2,E-03
4,E-03
Pilot L S E
kg
Ne
qk
g-
0
5
Pilot L S E M
kg
CO
2 e
q k
g
0,E+00
2,E-03
4,E-03
Pilot L S E
kg
Pe
qk
g
0,E+00
2,E-03
4,E-03
Pilot L S E
kg
Ne
qk
g-
0
5
Pilot L S E M
kg
CO
2 e
q k
g
LCA results: environmental sustainability of the Integrated systems
Backwash
wastewater
Backwash
wastewater
Backwash supernatant released in the sewage system
DigestateElectricity
HeatPikeperch
RAS
Fish sludge
Settling
Maize silageSoil conditioner
Treated backwash supernatant released in the sewage system
Valorisation as shrimp feed
Shrimp feed
Drying
Baseline scenario
Raceway ponds
MaB-floc liquor Dewatering
Heat
Biogas
Electricity to the grid
Scenario 1 - valorisation of MaB-flocs as shrimp feed
Pikeperch RAS Settling Milling
Digester CHP
Sustainable Pathways for Algal Bioenergy
Valorisation as biogas
Soil conditioner
MaB-floc liquor
Backwash
wastewater
Heat
Heat
DigestateElectricity
HeatFish sludge
DigesterMaize silage
Soil conditioner
Treated backwash supernatant released in the sewage system
Fish sludge
Maize silage
Digester Biogas
DigestateRaceway
ponds Dewatering
CHP
CHPBiogas Electricity to the grid
Electricityto the grid
Scenario 2 - valorisation of MaB-flocs as biogas
Pikeperch RAS Settling
LCA results: environmental sustainability of the Integrated systems
Resource footprint1
- 133%- 101%
Sustainable Pathways for Algal Bioenergy
Left bar: Right bar:
Avoided processes
1 CEENE results without abiotic renewable resources
LCA results: environmental sustainability of the Integrated systems
Freshwater eutrophication
(ReCiPe 2013)
Marine eutrophication
(ReCiPe 2013)
Carbon footprint(IPCC 2007)
Sustainable Pathways for Algal Bioenergy
Left bar: Right bar:
Avoided processes
ConclusionMaB-floc technology: stirring has the highest contribution to most impact categories
Integrated aquaculture waste treatment system:• Potential to compete with the baseline scenario and contribute to a
sustainable connection of the water-food-energy nexus in the aquaculture sector
Sustainable Pathways for Algal Bioenergy
• Valorizing MaB-flocs into shrimp feed: overall more sustainable than into biogas
Future research:• Improvement of LCA with more complete data on nutrient cycle
(measurements needed)
• Focus on the improvement of the energy efficiency of the system, rather than of MaB-flocs productivity
Bottleneck: EU legislation
Thank you!
+32 (0) 9 264 99 27
Sustainable Pathways for Algal Bioenergy
+32 (0) 9 264 99 27