Technologies for Microalgae Harvesting

2. 1. MICROALGAE – HARVESTING
2. HARVESTING TECHNIQUES
• Centrifugation
• Spiral plate Technique
• Flocculation
• Membrane Filtration
• Spray Drying
• Drum Drying
3. TABULATION
4. CONCLUSION
CONTENTS

3. 1. MICROALGAE – HARVESTING
1
• Microalgae or Microphytes are microscopic algae of
aquatic environment.
2
• Microalgae produce high-value compounds for
for human consumption products such as feed,
biofertilizers and bioenergy, as well as wastewater
treatment, nitrogen fixing and CO2 mitigation.

5. 2. HARVESTING TECHNIQUES
1
• The harvesting and dewatering is often expressed in
in qualitative terms , “high energy consumption” and
2
• It is necessary to analysis of different large-scale
harvesting and dewatering systems with focus on
processing energy consumption and resource
recovery.

7. A) CENTRIFUGATION
1
• 1.The driving force for separation during
centrifugation is the difference in density between
between the microalgae cells and solvent.
2
• The disc-stack centrifuge is suitable for the
harvesting of microalgae with a size of around 5 -
- 10 μm.

9. B) SPIRAL PLATE TECHNIQUE
1
• Spiral plate technology (SPT) is a three phase separator
(liquid/liquid/solid). Biomass is collected between rotating plates.
2
• The rotation is increased by centrifugal gravitational forces.
3
• At given times the operation is shortly interrupted to discharge the
collected biomass between the plates.
4
• The final biomass is likely paste or cake which may or may not undergo
drying based on their consumption.

11. C) FLOCCULATION
1
• Flocculants are a substance which promote the
clumping of fine particles into a floc. The floc may
float or sediment and filtered from the liquid.
2
• Flocculants like (Aluminium, Chitosan) interact with
interact with the surface of algae cells resulting in
in coagulation of algae.

13. D) MEMBRANE FILTRATION
1
• Algae solutions can be concentrated by membrane filtration. In Reverse
Osmosis (RO), water and small salt molecules permeate the filter.
2
• Microfiltration and Ultrafiltration can be applied for harvesting of
biomass and also for isolation of components.
3
• Ultrafiltration (UF) is used to retain larger organic molecules like proteins
and carbohydrates.
4
• Microfiltration (MF) can separate algal cells from the solution.

15. E) SPRAY DRYING
1
• In spray drying hot air (over 100 °C) is used to
to evaporate the water from atomized algae
droplets.
2
• Droplets are wet, so it subjected more heat to
recover biomass.

17. F) DRUM DRYING
1
• An alternative for spray drying is drum drying. For drum drying the algae
paste is distributed over a rotating drum, which is internally heated by
steam & dried biomass is collected.
2
• The temperatures in drum dryers can exceed protein denaturation
temperature & not preferred for obtaining high quality proteins.
3
• It is only for lipid containing biomass.

19. TECHNOLOGY STRENGTHS WEAKNESSES
Centrifugation • Continuous
• Efficient for large scale processing
• High capital cost
Spiral plate technology (SPT) • Efficient for small scale processing
• High recovery
• High capital cost
• Limited throughput capacity
Vacuum filtration • Continuous • Relative high harvesting cost
• Clogging or fouling
Membrane filtration • Efficient for small scale processing
• High recovery
• Fouling
• High capital cost
Sedimentation • Easy application
• Low energy demand
• Slow rates
• Large operational area
• Low recovery
• Limited application: suitable for large size algae
Chemical flocculation • Low energy demand
• Low equipment cost
• Difficult recovery of flocculants
Drum drying • Mature technology • High energy demand
Spray drying • Suitable for high value products • High energy demand
Solar drying • Low cost • Large drying surface
• Slow drying rate
• High risk for contamination and loss of mass
• Not for food grade products
3. TABULATION

20. 4. CONCLUSION
1
• Microalgae can be used to produce a wide range of
metabolites such as proteins, lipids, carbohydrates,
carotenoids or vitamins for health, food and feed
additives, cosmetics and for energy production.
2
• It is necessary to understand the harvesting techniques
techniques & applying them effectively.

21. Thank you