Symbiotic Integration Of Photobioreactors In A Factory building Façade For Mutual Benefit Between Buildings And Microalgae Needs

Abstract

The symbiosis with buildings appears as one promising way to reduce capital and operating cost of photobioreactor (PBR) technologies, while inducing in the same time some benefits on the building, like partial reduction of its energy consumption or even effluent emission. Large scale illuminated area are available, some costs like glasses can be shared, and the integration in a building façade allows aeraulic and fluid exchanges between building and PBRs to reduce needs in thermal regulation and nutrients supply (especially if CO2 sources are available). Optimization of the symbiosis is here critical, as the final interest of the concept will be here the result of mutual benefits obtained between buildings and microalgae needs. When considering the PBR only, its specific implantation in building façade also requires to solve technical challenges. The system geometry has to respond to architecture constraints, light capture has to be optimized to guarantee maximal performances, the process has to be robust with ideally a continuous and automated operation during several months… The design of the system reveals here critical, as well as the applied mixing conditions, or the material used.

Symbio2 is a R&D project which aims at developing advanced hybrid façade system optimising the concept of symbiosis between building and microalgal cultivation, by integrating thin flat panel microalgae PBRs in a factory façade where aeraulic and fluid exchanges between building and PBRs are optimized. For demonstration, a 300m² biofaçade is actually under development to demonstrate the economic and technical feasibility of this new approach to produce microalgae. This biofaçade will be set on a French waste processing plant in Nantes (www.alcea.fr).

The presentation will give main principles and challenges in the setting of an optimised symbiosis in the case of the plant implementation, to benefit especially from available CO2 contained in flue gas issued from solid waste incineration. A special focus will be made on the specific cultivations conditions involved by an implantation of a biomass production in vertical south-facing façade, and on their consequences on PBR running along the year and on maximal biomass productivity achievable in such systems (here discussed for the microalga Chlorella vulgaris). A model simulating the dynamic behaviour of microalgal cultivation systems in response to change in meteorological conditions will be presented. This will allow biomass productivity to be predicted and compared with standard cultivation systems (horizontal and inclined systems), emphasizing the interest, potential and limits of PBR implementation in building façade.

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http://www.gepea.fr/
Symbiotic Integration Of Photobioreactors In A Factory
Building Façade For Mutual Benefit Between
Buildings And Microalgae Needs
GEPEA : J.Pruvost, B.LE Gouic, J.Legrand
AlgoSource Technologies : F. Le Borgne, O.Lépine

Industrial interest of microalgae
Microalgae: a new vegetable feedstock with high potential
Composition
•Proteins
•Carbohydrates
•Lipids
•Specific metabolites: antioxidant,
pigments, PolyUnsaturated Fatty Acids,
TriAcylGlycerol, ExoPolySaccharides…
Application areas
•Food
•Feed
•Food supplement
•Biofuel production
•Pharmaceutical
•Cosmetics
•…
2

Solar cultivation systems
Open systems
Open ponds, raceways
Closed systems (photobioreactors)
Tubes, flat panels
Productivity : < 100 t/ha/year
Productivity : < 1 t/ha/year
Productivity : 10 - 30 t/ha/year
Better productivity, but more complex technology (and often higher cost) !
Closed photobioreactors :
•the only technology able to reach maximum conversion yield
•need to be intensified to be cost effective (high areal and
volumetric productivities)
Optimisation of solar energy use is a pre-requisite

Biofaçade PBR
THE SYMBIO2 PROJECT:
•Integration of a 300m² biofacade in a waste
processing plant (Nantes, France -
www.alcea.fr) for simultaneous microalgal
production and flue gas partial treatment
•The purpose is to demonstrate the economic
and technical feasibility of this new approach
to producing microalgae.
•Optimisation of the symbiosis is here critical,
as the final interest of the concept will be the
result of mutual benefits obtained between
buildings and microalgae needs.

Symbiosis of microalgae cultivation with buildings
An interesting way to reduce capital and operating cost of photobioreactor technologies
•Large scale illuminated areas are available
•Some costs like glasses can be shared
•The configuration in a double skin façade allows generating benefic interactions, with
aerolic and fluid exchanges between the building and the photobioreactors to reduce
operational costs, especially in the case of CO2and thermal regulation requirements
Thermal exchanges
CO2from the plant
Biomass with
valuable
coumpounds
X-TU Architects

Linking microalgae needs in nutrients with
building emissions
CO2+ 0.71 H2O + 0.14 HNO3+ 0.008 H2SO4+ 0.005 H3PO4→ CH1.59O0.55N0.14S0.008P0.005 +1.32 O2
Photoautotrophic growth of Arthospira platensis
50% of dry weight are carbon so 1kg of biomass can fix 1.5-1.8kg of CO2
Photosynthetic biomass could be a part of the
solution to fix anthropogenic carbon in a
sustainable way
… and there is an evident interest to develop a
circular biobased economy, in a “waste-to-
value” approach
Two major substrats : light (photosynthesis) and CO2
6
Can be combined to a partial depollution of liquid effluents (nitrate or ammonium,
phosphates…)
Mineral requirements

Linking microalgae needs in nutrients with
building emissions
7
0
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1E+18
2E+18
2E+18
3E+18
3E+18
4E+18
4E+18
5E+18
5E+18
250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000
Longueur d'onde n(m)
Flux incid ent (photons m
-2
.s
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.nm
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0
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1E+18
2E+18
2E+18
3E+18
3E+18
4E+18
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5E+18
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250 500 750 1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750 4000
Longueur d'onde n(m)
Flux incid ent (photons m
-2
.s
-1
.nm
-1
)
AlgoSolis experimental area, Saint-Nazaire
Thermal regulation
In solar conditions,
photobioreactors tend to a
significant over-heating
(even in winter) Lethal temperature
Photobioreactor without thermal
regulation in summer
Photosynthetic active radiation
(43% of sunlight energy)
And more than 85% are
converted in heat by
biological reactions

The concept is « sexy », but is microalgae cultivation in
building façade really interesting?
Prediction of Bio-Façade performances, and comparison
to usual cultivation systems

Prediction of biomass productivity
Irradiation conditions
(solar database – meteonorm.com)
Prediction of biomass
concentration
(productivity) time course
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Growth rate calculation
Pruvost et al., Biotech progress, 2013

Month of the year
Façade PBR: The effect of vertical inclination
Maximal biomass productivity (year average)
8.55g/m²/day = 34t/ha/year
(horizontal : 45t/ha/year)
CO2 biofixation = 50 - 60t/ha/year
Month of the year
•Vertical implantation leads to a decrease of light
intercepted (compared to horizontal systems : -20%)
•Because of the higher altitude angle in summer,
vertical implantation leads to very specific
irradiation conditions:
Almost constant operating conditions are encountered
all along the year a stable production all along the
year is expected
β

Façade PBR: comparison to other usual systems
Scenario investigated : Production of 1ton of dry biomass
5 g/m²/day
10 to 30 g/m3/day
Mixing 0.1 kWh/m3
Thermal regulation 0 kWh/m3
(no regulation)
8 g/m²/day
200/g/m3/day
Mixing 0.35 kWh/m3
Thermal regulation 1.1 kWh/m3
(0 if optimal symbiosis)
13 g/m²/day
260g/m3/day
Mixing 0.35 kWh/m3
Thermal regulation 1.1 kWh/m3
13 g/m²/day
6000g/m3/day
Mixing 0.35 kWh/m3
Thermal regulation 1.1 kWh/m3
(0 if passive regulation)
Façade PBR Raceway 45°inclination PBR AlgoFilm© PBR
(ultrathin system)
Production stage
Downstream processing stageDownstream processing stage

Façade PBR: comparison to other usual systems
•For a given biomass production objective, biofaçade PBR requests 2-fold less illuminated
surface than raceway
•Because of vertical inclination, lower performances are achieved compared to inclined
and horizontal systems (France location)
Surface immobilisation (illuminated surface) Simulated process line :
Cultivation + Biomass drying

Façade PBR: comparison to other usual systems
For a given production goal, biofaçade PBR request 5-fold less culture volume than raceways
Culture volume Simulated process line :
Cultivation + Biomass drying

Façade PBR: comparison to other usual systems
Thermal symbiosis with building reveals critical and can lead to a drastically decrease of energy
requirement (2-5-fold lower than standard PBR !)
Even
in the best case, EROEI
is
less
than
1

not
suitable
for
biofuel
production
Simulated process line :
Cultivation + Biomass drying
Energy requirement
Estimation of energy for thermal regulation
500kWh/m²/year
(no symbiosis)
200kWh/m²/year
(actual symbiosis)
0kWh/m²/year
(ideal case - optimal
symbiosis)
710kWh/m²/year
(no symbiosis)
180kWh/m²/year
(no symbiosis)
0kWh/m²/year
(ideal case - optimal
symbiosis)

Conclusion
Integration of photobioreactors in building façade appears as
an interesting approach. With appropriate symbiosis, CAPEX
(glass surface sharing) and OPEX (aerolic and fluid exchanges)
can be decreased
Vertical implantation induces specific operating conditions:
the non-optimal sunlight capitation could be (at least partly)
compensated by an easier operation of the process all along
the year
Compared to other conventional cultivation systems, CO2
feeding and thermal regulation appear as two key-aspects.
Their optimization can significantly decrease operational costs

Conclusion
Theoretical studies are currently completed by an extensive set of
experiments (indoor and outdoor)
The project will be concretized in a 300m² biofacade in a
waste processing plant (Nantes, France) for simultaneous
microalgal production (0.7-1t/year) and flue gas partial
treatment (CO2 biofixation: 1-1.8t/year)

http://www.gepea.fr/
Thank you for your
attention
AlgoSolis R&D platform
(outdoor facilities, 2015)
POLYTECH Nantes campus
Graduate School of Engineering
Chemical Eng. and bioprocess dept
GEPEA laboratory
Atlantique Ocean La Baule St Nazaire
AlgoSource Technologies
Biosolis experimental
outdoor area