Harvesting of Microalgal Biomass - Biotechnological Applications of Microalgae - page 77

6 Harvesting of

Microalgal Biomass

Manjinder Singh, Rekha Shukla, and Keshav Das
Biorefining and Carbon Cycling Program
College of Engineering
The University of Georgia
Athens, Georgia

CONTENTS
6.1 Introduction .................................................................................................... 77
6.2 Harvesting Processes ...................................................................................... 79
6.3 Gravity Sedimentation .................................................................................... 79
6.4 Centrifugation ................................................................................................. 80
6.5 Filtration ......................................................................................................... 80
6.6 Flotation .......................................................................................................... 81
6.7 Flocculation .................................................................................................... 81
6.8 Electrolytic Coagulation ................................................................................. 82
6.9 Energy Efficiencies of Harvesting Processes ................................................. 83
6.10 Conclusion ...................................................................................................... 85
References ................................................................................................................ 86

6.1 INTRODUCTION
Microalgae have been identified as a potential alternative resource for biofuel
production. Significant drawbacks to algaculture include dilute culture density and
the small size of microalgae, which translates into the need to handle large volumes
of culture during harvesting. This energy-intensive process is therefore considered
a major challenge for the commercial-scale production of algal biofuels. Most of
the currently used harvesting techniques have several drawbacks, such as high cost,
flocculant toxicity, or nonfeasibility of scale-up, which impact the cost and quality of
products. As harvesting cost may itself contribute up to one-third of the biomass pro-
duction cost, substantial amounts of research and development initiatives are needed
to develop a cost- and energy-effective process for the dewatering of algae. Several
factors, such as algae species, ionic strength of culture media, recycling of filtrate,
and final products, should be considered when selecting a suitable harvesting tech-
nique. Harvesting cost and energy requirements must be reduced by a factor of at
least 2 if algal biomass production is to be viable for very low-cost products such as
biofuels. There could be considerable cost and energy savings in custom-designed,

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