How it works
A raceway is a closed oval loop channel, shallow (typically 15–30 cm), through which the culture circulates driven by a paddlewheel. That movement keeps cells in suspension, homogenises light and nutrients and favours gas exchange with the atmosphere.
When it is used
It is the system of choice for species that tolerate selective or extreme conditions, which act as a natural barrier against contamination: Spirulina in alkaline waters or Dunaliella in hypersaline waters. For those cases, its low cost makes it unbeatable at large scale.
Advantages
- +Low investment and operating cost
- +Easy to scale to large areas
- +Simple to build and maintain
Limitations
- −Less control of temperature, light and pH
- −Higher contamination risk
- −Evaporation losses and lower cell density
FAQ
Mostly robust species or ones that tolerate selective conditions, such as Spirulina (alkaline waters), Chlorella or Dunaliella (hypersaline waters).
Because of their low cost and ease of scaling, which offset their lower control when the species tolerates pond conditions.
Sources
- Richmond, A. & Hu, Q. (eds.) (2013). Handbook of Microalgal Culture: Applied Phycology and Biotechnology. Wiley-Blackwell.
- Chisti, Y. (2007). Biodiesel from microalgae. Biotechnology Advances, 25(3), 294–306.
- Spolaore, P. et al. (2006). Commercial applications of microalgae. Journal of Bioscience and Bioengineering, 101(2), 87–96.
- Mata, T.M. et al. (2010). Microalgae for biodiesel production and other applications: A review. Renewable and Sustainable Energy Reviews, 14(1), 217–232.
Scientific outreach based on specialised literature. Scientific review: pending.