Open Ponds: Open ponds can be categorized into natural waters (lakes, lagoons, ponds) and artificial ponds or containers.
Advantages: open ponds cultivation system are much easier to construct and operate than other closed systems.
Disadvantages: There are many limitation of open ponds, including poor light utilization, diffusion of CO2 into atmosphere and require of large areas of land.
Raceway ponds: In these ponds, the algae, water & nutrients circulate around a racetrack. With paddlewheels providing the flow, algae are kept suspended in the water, and are circulated back to the surface on a regular frequency. The ponds are usually kept shallow because the algae need to be exposed to sunlight, and sunlight can only penetrate the pond water to a limited depth.
Advantages: Simplicity, resulting in low production costs and low operating costs.
Disadvantages: The environment in and around the pond is not completely under control. These factors including bad weather condition, bacterial in the algae strain and the temperature in the raceway ponds.
Photobioreactors: A photobioreactor is a closed equipment which provides a controlled environment and enables high productivity of algae.
Advantages of Photobioreactors:
Cultivation of algae is in controlled circumstances, hence potential for much higher productivity.
Large surface-to-volume ratio. PBRs offer maximum efficiency in using light and therefore greatly improve productivity. Typically the culture density of algae produced is 10 to 20 times greater than bag culture in which algaeculture is done in bags - and can be even greater.
Better control of gas transfer.
Reduction in evaporation of growth medium.
More uniform temperature.
Better protection from outside contamination.
Space saving - Can be mounted vertically, horizontally or at an angle, indoors or outdoors.
Reduced Fouling - Recently available tube self cleaning mechanisms can dramatically reduce fouling.
Disadvantages:
Cost a lot of money.
Despite higher biomass concentration and better control of culture parameters, data accumulated in the last two decades have shown that the productivity and production cost in some enclosed photobioreactor systems are not much better than those achievable in open-pond cultures.
The technical difficulty in sterilizing these photobioreactors has hindered their application for algae culture for specific end-products such as high value pharmaceutical products.