The bottlenecks that restrict commercial production of microalgal bioenergy have recently been summarized as “high cost” and
“low efficiency” [13]. However, there are ways to optimize open
systems. Microalgae cultivation in wastewater, recycling of water
and nutrients, utilization of the whole biomass, selection of indigenous strains, and optimization of the harvesting technique are
Fig. 1 Open raceway pond where the algal cultivation is circulated through the track by paddle wheels. Picture:
JanB46, Wikipedia, CC BY-SA 3.0
Table 2
Advantages and disadvantages of common cultivation systems, adapted from Pulz [7]
Cultivation system Advantages
Disadvantages
Open
l
Relatively cheap
l
High risk of contamination
l
Good gas exchange with the atmosphere
(e.g., release of O 2 )
l
High evaporation losses
l
Large area required
l
Easy to operate
l
Easy to scale up
l
Cooling by evaporation
l
Light limitation if thick
layers are used
Closed
l
Good control of cultivation parameters
l
High productivity
l
Expensive to build and
operate
l
Reduced contamination risk
l
Less CO 2 losses
l
Requires in most cases
cooling
l
Reproducible cultivation conditions
l
Scale up is difficult
Large Scale Cultivation of Microalgae
3