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Cyanobacterial biomass harvesting techniques. (a) Sedimentation, (b) Flocculation, (c) Filtration, (d) Froth flotation and (e) Centrifugation. The advantages (✓) and disadvantages (X) of each techniques mentioned
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Pigments are intensely coloured compounds used in many industries to colour other materials. The demand for naturally synthesised pigments is increasing and their production can be incorporated into circular bioeconomy approaches. Natural pigments are produced by bacteria, cyanobacteria, microalgae, macroalgae, plants and animals. There is a huge u...
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... can be applied as the first step of dewatering (Fig. 5a). During sedimentation different materials are separated from one another based on their density and/or particle size [289]. Gravity sedimentation naturally separates a feed suspension into a concentrated slurry and clear liquid. Harvesting by sedimentation at natural gravity can be accomplished via lamella separators (plates installed ...
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... is used to increase the efficiency of sedimentation or flotation-based dewatering (Fig. 5b). Here, a particle in a solution forms an aggregate with other particles to form flocs [292][293][294]. Flocculation occurs when the solute particles interact and adhere to each other. Chemical flocculation can be induced by inorganic flocculants (e.g. alum, ferric sulphate, lime) [294] or organic polymer and polyelectrolyte flocculants ...
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... flotation is a physiochemical gravity separation technique based on density differences between the cells and the aqueous phase [297][298][299]. Air is pumped into the flotation unit with or without an additional organic/inorganic chemical, and the resultant bubbling causes biomass accumulation along with the froth of bubbles at the top phase (Fig. 5c) [300]. This froth layer is separated and treated to harvest the biomass [301]. The flotation process can be subdivided according to the methods used for the bubble formation (e.g. dispersed air flotation, dissolved air flotation, microbubble generation and electrolytic flotation [300]). Flotation can also be combined with flocculation ...
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... according to the methods used for the bubble formation (e.g. dispersed air flotation, dissolved air flotation, microbubble generation and electrolytic flotation [300]). Flotation can also be combined with flocculation technique to separate a floating floc layer [300]. The advantages and disadvantages of froth flotation are summarised in Fig. ...
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... utilises a permeable size-exclusion based material through which a suspension is passed to separate smaller (e.g. aqueous phase) from larger molecules or particles (e.g. cells). Membrane filtration (tangential flow/cross-flow filtration) is the most commonly used harvest technique in Spirulina sp. farms [302,303] (Fig. 5d). Filtration requires a pressure difference across the filter which can be driven by gravity, applied pressure or the use of a vacuum [303,304]. Membrane filters are classified based on the pore size into macro-(greater than 10 μm), micro-(0.1-10 μm) and ultrafiltration (0.02-0.20 μm) as well as reverse osmosis (<0.001 μm) [305]. ...
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... applies centrifugal force to enhance the dewatering efficiency (Fig. 5e) [307,308]. Spinning the cell suspension creates the differential pressure necessary for a particle to separate from the liquid. The efficiency of the recovery process is dependent on the centrifugal force, particle size and density [308]. The two common types of centrifuges used for microalgae are disc stack and decanter centrifuges ...
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Citations
We are increasingly challenged to operate within our planetary boundaries, while delivering on United Nations (UN) Sustainable Development Goal (SDG) 2030 targets, and net-zero emissions by 2050. Failure to solve these challenges risks economic, social, political, climate, food, water, and fuel security. Therefore, new, scalable, and adoptable circular economy solutions are urgently required. The ability of plants to use light, capture CO2, and drive complex biochemistry is pivotal to delivering these solutions. However, harnessing this capability efficiently also requires robust accompanying economic, financial, market, and strategic analytics. A framework for this is presented here in the Commercialization Tourbillon. It supports the delivery of emerging plant biotechnologies and bio-inspired light-driven industry solutions within the critical 2030-2050 timeframe, to achieve validated economic, social, and environmental benefits.
