Open Pond vs Photobioreactor
Producers of high-quality algae are often part of a complex supply chain due to different applicable ways of utilisation: A buyer of the algae processes the biomass into the end product, such as a dietary supplement or cosmetics. In this case the algae producer is a supplier with corresponding delivery obligations. In order to avoid delivery problems, it is therefore important for him to be able to plan and maintain his production volume and product quality as well as possible.
There are different methods for growing algae. However, not all of these methods can ensure the reliable output required in the corresponding supply chain.
Open Pond vs Photobioreactor
Two commonly used methods for growing algae are the open pond and the closed photobioreactor. The open pond (or open raceway pond because of its characteristic shape) is an artificial pond that is usually no deeper than 30 cm. With the help of incoming sunlight, the algae in the open pond photosynthesise and proliferate. Open pond production sites are often several hectares in size because the amount of algae that can be grown in such a system is directly related to the size of the water surface available for solar radiation.
In a closed photobioreactor, the algae reproduce in a closed container. For example, in a glass tubular photobioreactor, the algae flow in a culture solution through long glass tubes with a diameter of 5 cm. The light can enter the tubes from all sides and stimulate the algae to photosynthesise. The key difference to the open pond: In closed photobioreactors, the algae is separated from direct environmental influences.
Agriculture vs. Industrial Production
Companies that grow algae in open ponds are subject to agricultural circumstances, because they cannot comprehensively control the conditions of their cultivation – resulting in various challenges to cope with:
- If the ambient temperature rises or falls too drastically, so does the water temperature and the algae no longer proliferate.
- Excessive precipitation causes the open ponds to overflow.
- Above all, open ponds are exposed to the risk of being polluted or contaminated with foreign organisms due to their freely accessible water surface. Foreign algae, bacteria, rotifiers and other parasites can damage the algae culture. In the worst case a culture crash might occur. The result: The complete cultivation has to be disposed of and has to be restarted. The algae farmer loses up to three weeks of production in the affected open pond.
This means that even open pond producers which are operating very efficiently, cannot produce 365 days a year, but usually only up to eight months. However, this is only possible if they control their processes thoroughly and have chosen an optimal location for their open ponds.
In a closed photobioreactor, on the other hand, the conditions for growing algae can be optimally adjusted and kept constant:
- By means of various heat management measures, the temperature in the system can be regulated in such a way that optimal conditions for the production of biomass prevail all year round.
- The pH value and the CO2 concentration of the water can be precisely adjusted to the requirements of the algae.
- The concentration of oxygen can be controlled accurately so that algae growth is not inhibited.
- The concentration of nutrients such as phosphorus and nitrogen can be balanced so that the algae are optimally supplied.
- Particularly important: With careful operation contamination from the environment is virtually impossible in a glass tubular photobioreactor.
In contrast to an open pond, a closed photobioreactor is an industrial production plant. Because the production conditions can be kept stable, it can be used to produce the desired amount of biomass with a constant lipid profile all year round without major interruptions.
Producers of algae in open ponds have to live with the fact that in one month they could achieve an optimal output, but it the next it may decrease by more than half, and in some months they can’t produce anything at all. Glass tubular photobioreactors, on the other hand, reliably produce the quantity and quality of biomass that is expected from purchasers in a supply chain.