Technical evaluation of photobioreactors for microalgae cultivation

Abstract

Abstract. This paper undertakes the description and assessment of various solutions applied for the design of photobioreactors as the type of apparatus, which can provide high output of green algae biomass. The design of such apparatus plays an important role in the context of the concurrent fulfillment of ecological and economic requirements, which are necessary to conduct an efficient and effective technology using cheap and easily accessible resources to produce different goods. Nowadays, algae is seen as one of the most promising sustainable way to produce energy in the future (biofuels, electricity, thermal energy) but technologies of biomass production and processing are still under development particularly to increase biomass and energy output. The cultivation costs in closed systems are still high, limiting their commercial applications to high-valued compounds but they can be reduced by efficient bioreactor designs, which are able to achieve high areal biomass productivities. This paper focuses on the advantages and drawbacks associated with the application of the particular types of bioreactors in algae production, description of their operation parameters and area for practical application, pointing of the constructions (tubular, flat panel, bubble column) that can contribute to improvement the profitability of large-scale production.

Biophotonics for improving algal photobioreactor performance: A review

“…Despite its mixing and mass transfer efficiency, the STR has high energy demand thus making it less economical for algaculture. The design also possesses a very low surface to volume ( SA / V ) ratio (due to its cylindrical shape) which in turn reduces photosynthetic efficiency of the microalgae . Biomass productivity in this design can be as low as 30‐50 mg (L·d) –1 …”

“…A circulation pump ensures liquid flow as well as air and media supply in the bags. This PBR design has been characterized by a good SA / V . Scenedesmus obliquus has been successfully cultured in plastic bag PBRs for biofuel production achieving a biomass productivity rate of 140 mg (L·d) –1 .…”

“…This design (Figure ) is comprised of an upright structure, of cylindrical, pyramidal, or conical shape, around which a flexible small diameter tube is wound. The tubes generally have a diameter range of 2.4‐5 cm, and media circulation is facilitated by pumps …”

“…The helical design offers good relations between energy consumption and the effectiveness of photosynthesis. It also has uniform mixing capabilities and effective CO 2 mass transfer from the gaseous to the liquid phase . This design was effectively used to culture Chlorella sp.…”

“…PBRs are the conventional closed algaculture system. They offer a more controllable culture microenvironment, limit contamination by unwanted algal species, limit water loss through evaporation and invasion by predators, and ultimately these are associated with high algae biomass production . According to Chisti, typical biomass productivities in PBR systems are at least 30 times greater than those achieved in open raceway ponds.…”