Understanding the best way to plan production and produce consistent quality
This article is an extract from our e-book “Comparison of commonly used technologies for the cultivation of algae: Open Raceway Ponds, Tubular Glass Photobioreactors and systems with disposable polymer materials“.
The goal of algae production is the growth of biomass such as spirulina or the extraction of valuable ingredients such as astaxanthin or DHA. A multi-stage, step-by-step process is usually required to get to the final product. Furthermore, the products are often supplied within delivery chains to other organizations for further processing into gel caps or freeze dried, before they are packaged.
When comparing methods of industrial algae production – What is important?
There are different methods of cultivating algae. However, two aspects are particularly important for the industrial production and processing of algae:
- How reliable can algae production processes be planned?
- How accurate can the algae production output be predicted?
Below we compare three different well-known algae cultivation methods: Open Raceway Ponds, Tubular Glass Photobioreactors and Plastic Bags. Open Raceway Ponds (ORP) are the most widespread method and originate from natural ponds. Tubular Glass Photobioreactors (PBR) have been reliably in operation for almost 20 years, indoors and outdoors. Also plastic bag systems made of disposable polymers are particularly popular. Green Wall Panels (GWP) are a variant of the plastic bag systems.
Contamination is a determining factor
The major impact that affects output, is contamination of the algae culture with foreign organisms. The level of risk of contamination in the different algae production systems must be clarified. Organisms can contaminate the liquid solution and biofouling can occur on the inner surface of the container. Contamination can result from the influence of various factors:
Level of algae concentration
The higher the concentration of algae in the liquid solution, the more stable the culture is. If there are indeed foreign organisms in the liquid, they will face great difficulty in multiplying in an environment dominated by algae.
This gives rise to the question – Which cultivation method can work with high concentrations of algae?
Studies show the following concentrations of algae at harvest:
Tubular glass PBRs as algae production systems have, as stated, especially advantageous surface-to-volume ratio. Moreover, optical paths within the tubes are very short. Algae concentrations in glass tubes are therefore up to 50 times higher than in ORPs.
Protecting the liquid solution from atmospheric influences
The risk of having production processes malfunction because of contamination is especially high when foreign organisms can easily access the liquid. In this regard, closed cultivation processes have an advantage over open ones.
In the comparison of tubular glass PBR, GWP and ORP, this means:
It is obvious that algae production processes in tubular glass PBRs can be easily planned and production output reliably predicted. This is a result of the fact that two important factors that influence the risk of contamination of the liquid solution are eliminated in tubular glass PBRs:
- Tubular glass PBRs seal off the liquid solution from the atmosphere, therefore no foreign organisms can penetrate from the outside.
- If foreign organisms do enter the liquid solution, they will face difficulties to take over the culture because the high algae concentration in tubular glass PBRs largely limit their multiplication.