The best choice: High end glass for your photobioreactor

Benefits of using high end glass for your photobioreactor

Glass tubes by SCHOTT are a very good choice, if you are planning to construct a photobioreactor (PBR) for productive, high quality and cost efficient algae cultivation. PBRs with our glass tubes are characterized by six clear benefits:
 

Bio secure

Algae cultivation in SCHOTT glass systems is bio-secure. The cultivation solution in our components is protected against bio-contamination and culture crashes.

The main reason is when using a tubular PBR, the algae cultivation takes place in a closed system. Therefore, extraneous organisms from the atmosphere are not able to invade the cultivation solution. Additionally, the container material glass with its minimal surface roughness, and the geometry of the tube, ensure that the development of biofilm on the inside of the PBR is prevented. The high processing quality of the tube ends and the custom fit tube couplings further minimize the formation of biofilm.
 

Food safe

PBRs with glass tubes as containers guarantee the highest quality within algae cultivation. The produced biomass is not only food grade but also pharma grade.

On the contrary, open ponds are faced with the problem of the cultivation solution not being separated from the atmosphere. Extraneous organisms can therefore easily enter the pond and minimize the quality of the algae.

On the other hand, when using containers made of plastics, one must examine very closely if certain substances possibly detach from the plastic during algae cultivation, which should not be found within
dietary supplements.

Not only the glass tubes but also the tube couplings by SCHOTT are, in accordance to the guidelines of the FDA (U.S. Food and Drug Administration), food grade and therefore authorized to be in contact with dietary products.

 

Resistant

The tubes of a glass PBR are made of borosilicate glass. Glass in general, and more specifically DURAN® borosilicate glass, is particularly consistent against environmental impacts, which is significant during algae cultivation. This glass is:
  • UV-stable - even decades under UV radiation does not impair the productivity of a glass PBR (in comparison to a polymer PBR).
  • Chemically stable -  the glass tubes can be cleaned and disinfected with numerous chemical solutions.
  • Mechanically stable - glass tubes only scratch under massive impact. Therefore, there is no problem in mechanically cleaning them or installing and dismantling them on numerous occasions.
  • Salt resistant - saltwater, which is required for the cultivation solution for some algae, does not result in the container corroding over time.
  • Stable against sagging - due to glass being particularly firm, the glass tubes can be elevated with considerably less brackets and still do not sag.
Durable

Durable

Borosilicate glass as a material is extremely durable against numerous environmental impacts. Therefore, glass tubes clearly display the longest service life in outdoor operation: 50 years and more. Polymers, in contrast, degrade within 1–10 years depending on the material used: Containers made of PVC need to be replaced every 2-5 years and containers made of PMMA every 8-12 years. Experience shows that the polymer liner of an open pond must be replaced after 20–25 years. Polymer bags must be replaced annually due to heavy biofilm formation and transmission losses due to UV rays.

Learn more about this topic: Comparison of commonly used technologies for the cultivation of algae
Productivity

Productivity

Tubular glass PBRs are particularly productive. There are two reasons for this: On the one hand, glass tubes allow one to host as much photoactive volume of cultivation solution on a given area than any other algae cultivation method. For example with a PBR height of about 6 meters, one could theoretically work with up to 200 litres of photoactive volume on one square meter surface area. On the other hand, algae in glass tube PBRs grows very quickly: Depending on the location and lighting conditions, growth rates between 0.3 and 0.6 grams per litre are possible. These two factors lead to the fact that tubular glass PBRs offer the highest areal productivity of all cultivation methods.

In the study below, the comparison of widespread algae cultivation methods results in a clear picture:

Tubular glass PBRs are able to produce 50-90 tons of biomass per hectare per year. This is up to 10 times more than in open ponds and up to 3 times more than in plastic bags.

Learn more about this topic: Comparison of commonly used technologies for the cultivation of algae

Cost efficient

In industrial applications, with decade long running installations, glass tube PBRs are particularly cost efficient. The costs of initial investment are often higher than with other cultivation methods. This however, relativizes itself when taking a closer look at the implementation of an open pond might be comparably cost efficient. If one desires to produce the same amount of biomass in an open pond then up to 10 times the surface area is needed compared to a tubular glass PBR.

Additionally, up to 20% of the solution in open systems evaporates on hot days. This loss of solution needs to constantly be refilled. Furthermore, the energy costs during algae harvesting are significantly higher, due to the low algae concentration at the time of harvest having to be centrifuged with water.

Closed plastic systems are – apart from plastic bags – similarly expensive in their initial procurement as tubular glass PBRs of the same volume. Depending on the polymer variety, the material however, degrades so quickly that the plastic container needs to be replaced every 2-10 years. These procurement costs therefore come up as replacement investments again and again. Due to the great difficulty to clean plastic bags, they would  need to be replaced annually. With an algae cultivation period of 50 years, plastic containers would need to be replaced 5-50 times. Additionally the respective costs for labor, materials, disposal and production interruptions would need to be incorporated. On the contrary, a glass system can produce for up to 50 years at the same productivity. The operating costs differentiate as well: Plastic systems are clearly more high maintenance than glass systems.

Learn more about this topic: Comparison of commonly used technologies for the cultivation of algae
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