GOVERNING EXPONENTIAL GROWTH RATES OF HIGH-DENSITY MICROALGAE CULTURES BY AUTOMATED ADJUSTMENT OF AERATION IN FLAT PANEL AIRLIFT PHOTOBIOREACTORS (POSTER 336)

Subitec GmbH | Sustainable Biotechnology | Stuttgart | Germany Steffen Welzmiller | s.welzmiller@subitec.com | www.subitec.com

!  Subitec GmbH – who we are and what we do

!  Motivation

!  Limits of mass cultivation – Light

!  Experimental layout

!  Light saturation and aeration rate

!  Conclusion / outlook

Content

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SUBITEC GMBH – WHO WE ARE AND WHAT WE DO

> Spin-off from the Fraunhofer-Institute for Interfacial Engineering

and Biotechnolgy (IGB) in Germany Stuttgart

> Foundation of the enterprise in 2000

> Holding two patent families regarding the Flat-Panel-Airlift

Photobioreactors (FPA)

> First pilot plants in 2008

> Since 2013 design and construction of scale-up and production

plants

> Employees: 14

Subitec: We have evolved from a Spin-off of a R&D organization into a Plant Manufacturer

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!  Design addresses inhibitive effects of

photolimitation and photoinhibition

!  High Productivityvol. (up to 2 gDW L-1 d-1)

!  High biomass concentration (up to 20 gDW L-1)

!  No chemical/gaseous gradients

!  Straightforward process control

!  Modularity

!  Low CAPEX and OPEX

The Technology: The Flat-Panel-Airlift Photobioreactor (FPA) allows efficient light utilization

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Light

What We Offer

!  Systems for the cultivation of microalgae based on 6 L, 28 L and 180 L FPA-

PBRs

!  Laboratory applications, pilot- and large scale plants

!  Indoor and outdoor

!  Engineering, construction and commissioning of plants

!  R&D partner for microalgae based projects

!  Development, optimization and adaptation of microalgal cultivation and product

formation processes

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Subitec is building Industrial-Scale Plants For example the following project:

Market segment: Industrial-scale plant for the production of Astaxanthin

Dimension: approx. 700 photobioreactors with a volume of around 130 m3 (= 130.000 l ~ 34.000 gal) installed on a surface equivalent to a soccer field

Scope of Services: > Conceptional study regarding business model and local setting on

site

> Research and technological development

> Basic und Detailed Engineering

> Construction and commissioning of the plant

> Training and support 7

Visual Impressions

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MOTIVATION

Motivation

!  Make microalgae biotechnology commercially viable and competitive

▸  OPEX reduction of the cultivation process

!  Improve light utilization

!  Minimize energy demand

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LIMITS OF MASS CULTIVATION – LIGHT

Light Attenuation !  Absorption (self shading)

!  Surface reflection

!  Water reflection

!  Bubble reflection

!  Typical growth phases (lag, log, declining growth,

stationary, death)

▶  Increase photon flux density (PFD)

▶  Increase convective mass transfer

(turbulence, in FPA-PBR = aeration rate)

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EXPERIMENTAL LAYOUT

Experimental Layout

!  Thermosynechococcus elongatus BP-1

!  Temperature: 55°C / 130°F

!  HPS lamps

!  Modified BG11 (3-fold conc.)

!  Light saturation experiments: !  Fixed air: 180 L h-1 air (6% v/v CO2) !  Variations in light: 120..1020 µmol m-2 s-1

!  Aeration rate experiments: !  Fixed light: 780, 405 and 180 µmol m-2 s-1

!  Variations in airation: 40..300 L h-1 air (6% v/v CO2)

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LIGHT SATURATION AND AERATION RATE

Solely increase in PFD can not cope with light attenuation affects

!  N = 5

!  Light saturation at around 500 µmol m-2 s-1 (given set-up)

!  During bright sunlight 75% of PAR is not used

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Increase in PFD and aeration rate copes with light attenuation affects

!  780 µmol m-2 s-1 (> 500 µmol m-2 s-1 )

!  N = 3..7

!  Coordinate translation + fit

!  Allows for profitability assessment

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In other words: At intense light increasing the aeration rate is useful

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780 µmol m-2 s-1

Productivity Course over Dry Weight:

At bad light conditions high aeration rates are wasted energy

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780 µmol m-2 s-1

High aeration rates are useful

405 µmol m-2 s-1

Aeration rates > 180 l/h are wasted energy

180 µmol m-2 s-1

Aeration rates > 40 l/h are wasted energy

Energy reduction of at least 45 % is possible

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45 % Energy reduction 60 % Energy reduction

Estimation of Energy Reduction by Adjusted Aeration:

CONCLUSIONS / OUTLOOK

Summarized Conclusions

!  Light attenuation is evident

!  Light attenuation can partially be coped with by adapted aeration rate

!  Control parameters of the aeration rate should be the light intensity and the biomass concentration

!  Adjustment allows for

!  increased productivity at intense light and high biomass concentration

!  low-energy cultivation during dim light or low biomass concentration

!  Energy reduction of at least 45 % is possible

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Outlook

▶  Increase the cost effectiveness of cultivating microalgae by using the effects pointed

out

▶ Automation by instrumentation, control and automation (ICA) technologies

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!  Non-invasive technology

!  Precise online measurement

!  Automate feeding / dilution

!  Powerful tool in connection with day courses

(photolimitation, photoinhibition, respiration)

Note: Online DW Measurement at High Concentrations is a powerful tool in connection with day courses

(Correllation factor DW/OD = 0.28)

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THANKS TO PETER BERGMANN AND THE TEAM

THANK YOU FOR YOUR ATTENTION S.WELZMILLER@SUBITEC.COM