The wastewater treatment plant as a gold mine?

Biotechnology, Raw Materials, digitalization

Because of the global population growth, a new city of the size of Geneva needs to be supplied with food, water or energy every day. Many raw materials are in short supply and the situation will get worse in the future. We have already reported on some bottlenecks where biotechnology can provide solutions (Corona pandemy, drug shortage, plastic crisis, flavour & fragrance ).   

The shift to a sustainable economy and sustainable value chains makes the situation even more complex. The demand for raw materials, which are indispensable for this transition, will exceed the supply. For example, the transition from petroleum to renewable energy supply requires vast quantities of metals such as lithium, manganese, nickel, cobalt, and especially copper. This is why copper is also being referred to as "the new oil. Critical voices even claim that the planned energy turnaround threatens to fail due to the "biggest supply gap of all time".

With all these gloomy forecasts, there is something crucial to keep in mind: There are opportunities for universities and innovative companies that have the courage to get involved early in these areas of development. This also applies to another foreseeable bottleneck that we would like to report on here of which the general public is not aware but, in terms of its scope, should have the highest priority. We are talking about phosphorus.

Phosphorus - basic building block for plant and animal life

In addition to industrial applications, phosphorus is an absolutely elementary and irreplaceable element for life: an important component of our bones, teeth, DNA, energy storage and much more. Above all, phosphorus is irreplaceable in intensive agriculture. While raw material shortages can, in many cases, be replaced by different technologies, processes or products, this is not possible with phosphorus. There is no alternative for this raw material in agriculture. The price of phosphorus has therefore increased fivefold in recent years. We are dependent on being able to mine raw phosphates. However, these phosphate ore reserves are limited to five countries - Morocco, Jordan, South Africa, China and the USA - with 75 percent of known mineable reserves in Morocco. Phosphate mining is expected to peak between 2030 and 2040. In order to secure supplies for the world's growing population, phosphate recovery is becoming an inevitable step.

Sewage treatment plants are a rich source of phosphate. In Switzerland, almost 200,000 tons of sewage sludge are produced each year. This (dewatered) sewage sludge contains about 1 percent phosphorus. Yet the use of sewage sludge as fertilizer has been prohibited in Switzerland since 2006 due to contamination with heavy metals and must therefore be incinerated (see website of the Federal Office for the Environment, FOEN: According to a FOEN study, sewage sludge ash contains 6 percent phosphorus, which corresponds to about 6,000 tons of recoverable phosphorus annually. Phosphorus can also be eliminated by precipitation, e.g. as iron phosphate from wastewater - but this would again have to be purified from toxic heavy metals.

Phosphorus recovery with microbial fuel cells

The research group led by Fabian Fischer ( of the Institute Life Technologies at the University of Applied Sciences of Western Switzerland (HES-SO) in Sion is taking a different approach: he and his team are developing microbial fuel cells and use the electrical energy extracted from wastewater for phosphorus recovery. This way, phosphorus can be recovered directly from the sewage sludge and the problem of contamination with heavy metals can be circumvented. The microbial fuel cell provides energy, electrons and protons to recover phosphates in the form of struvite (NH4MgPO4) with a yield of over 80 percent. The process has already been successfully tested in small pilot plants. The chemical reaction is:

H3PO4 + MgCl2 + NH4OH  NH4MgPO4 + 2HCl + H2O

The stable, continuous operation of such bioelectric cascade reactors is a challenge. The dynamics of the biofilms and process parameters must be kept within the optimum range using computer-aided measurement and control technology. Incidentally, microbial fuel cells can also be used to recycle other metals. By the way, the weak current generated by the microbial oxidation of organic could also be stored in commercially available batteries at high levels using voltage converters.

Overcoming bottlenecks with biotechnology applications 

Biotechnology plays an important role in addressing bottlenecks, of which phosphorus is a good example. Other examples show how diverse the affected industries are: Biotech-derived meat, egg, honey or cocoa substitutes, for example, are already on the market or about to be launched. Hermès began marketing a vegan, leather-free mushroom-based bag this year. The construction industry is testing bio-cement and bio-bricks, and so on.

The "Industrial Biotechnology" working group, set up jointly by SATW and the SBA (Swiss Biotech Association), is looking at the industrial application of biotechnology. Switzerland should build on the success of red biotechnology (biopharmaceuticals) and establish a strong, well-connected industrial biotechnology community with a clear vision for areas of interest, a strategic research and education agenda, and an action plan.

Comments are, as always, very welcome!

Hans-Peter Meyer (Expertinova AG), SATW Member, Head working group Biotechnology