Which algae cultivation method has the lower TCO: PBRs with glass tubing or with plastic containers?

[Global] When we are choosing a glass or plastic made photobioreactor (PBR) to grow algae, at first thought, it might seem that plastic could be cheaper. But is that really the case?

The cost of algae cultivation over the lifetime of a PBR is one of the most important criteria to think about. However, calculation of the total cost of ownership (TCO) is very complex. This is not as simple as summarizing the costs of initial investment. The reinvestment and operating costs over the entire lifespan of the PBR is as important as the initial costs. In this article, German base company SCHOTT AG,  with decades of experience and expert knowledge on glasswares manufacturing, reveals the insight of the investment profile of a glass PBR system.

Glass versus Polyethylene

Polyethylene (PE) tubes are a particular economical variant made of polymer. However, microalgae biofilm forms easily on the PE tube wall, and it is easily degraded by UV irradiation. Therefore, PE tubing must be replaced every year.

Glass tubes on the other hand, cost twice as much as PE tubes, but lasts at least 50 years. The cost for producing one kilogram of biomass with PE tubes will therefore be significantly higher than with glass tubes.

Glass tubing in PBR is indeed a long-term-low-cost choice to grow algae. Despite the fact that plastic initially incur lower costs than glass, but the cheaper the plastic is, the sooner it needs a replacement. Think about its productivity, which might be affect by biofilm buildup, corrosion and UV irradiation.

Glass versus more durable polymer variants

PBR made of more durable polymer variants cost the same or even more expensive than glass. While glass tubing guarantees a 50 years lifespan, a long-serving polymer PBRs tubing may need a replacement after 10–12 years.

Many first-time users of PBR who are analyzing the costs of PBR system are surprised that glass system is actually the most economical choice. For a large scale PBR system requiring a large number of glass tubes, it is possible to reach a CAPEX of one Euro per liter for glass tubes with a service life of 50 years – an investment that is not feasible with any polymer material.

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This text is an excerpt from our e-book “Comparison of commonly used technologies for the cultivation of algae”. Download it for free.

 

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