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Interview with Dr. Christina Kuchendorf, researcher and project coordinator at the Institute of Bio- and Geosciences, IBG-2, at Forschungszentrum Jülich GmbH

Mrs. Kuchendorf, you work with algae at the Research Center in Jülich. Algae are believed to play an important role in the future of nutrition. What are the extraordinary abilities of algae in general?

Microalgae are ancient organisms. They have been on this planet for over a billion years and have adapted to all conceivable habitats. Since they are unicellular organisms, they reproduce much faster than higher land plants. Under optimal conditions, i.e. light, heat, CO2 and sufficient nutrients, they divide daily. The original habitat of microalgae is the oceans, where nutrients are distributed very thinly. This has made them food artists. They can absorb nutrients with their entire cell surface. They can also absorb and store much more nutrients than they need in the short term. The rapid growth under conditions that are beneficial to them, as well as the efficient absorption and "bunkering" of nutrients, makes microalgae a biomass resource that can be used in a variety of ways. On the one hand, it is pure biomass that can be used as a nutrient in food or feed; this is already happening, for example, in aquacultures for fish, but due to its high nutrient and mineral content it can also be used for our diet and can help to compensate for nutritional deficiencies. On the other hand, the diverse ingredients of algae are interesting as food or pharmaceutical additives, for example as colorants or antioxidants; but their oils and carbohydrates are not only interesting for nutrients, but also for (bio)cosmetics or even bioenergy; while the former can be very profitable economically, the technology is already available for the latter, but the costs are still very high - among other things, because separating the algae from their growth environment, the water, is relatively costly. Nevertheless, the technologies with which algae can be produced have a great advantage - they do not have to be installed on agricultural land and can even be integrated into architecture; and they can be connected to other material flows, for example solar energy, biogas, or rainwater and wastewater. The aspect of nutrient uptake is particularly interesting here, because the biomass can also be used as fertilizer; its ingredients fit the needs of plants very well.

The exhibition for the Bio-economy Year at MS Wissenschaft features a science exhibit from Forschungszentrum Jülich. "Clean water through algae" illustrates how a lawn of algae filters dirt as well as nutrients from wastewater, which can then be "scraped off" and processed. What advantages does this future technology offer compared to the usual processing of wastewater in sewage treatment plants?

In 2018, a pilot plant for so-called AlgalTurfScrubbing was installed for the first time in Germany at the Jülich Research Center's wastewater treatment plant. In this process, wastewater is fed into a channel system, a so-called floway, in which a turf of algae grows. As they grow, the algae absorb nutrients from the water and thus clean it. Every 4-14 days - depending on the weather, nutrient content of the water and growth rate - the nutrient-laden algae are harvested; this depends on the size of the plant. The technique is simple, inexpensive and applicable in many places. The AlgalFlipper at MS Wissenschaft illustrates this AlgalTurfScrubbing. Blue and green balls representing water and nutrients are directed onto a surface representing an algae turf. The nutrient balls are magnetically attached to the surface, the water balls continue to flow and can be returned to the beginning with an Archimedean screw. The nutrient balls can be "harvested" with a scrubber. They can then be returned to the cycle.

The algae flipper illustrates a very simple process in which microalgae form a biofilm on a surface over which wastewater is passed. In doing so, they should absorb nutrients such as the finite and globally very unevenly distributed phosphorus and the nitrogen that is abundantly produced in fertilization and livestock breeding - and they do so very effectively. The main product is clean water, which no longer contains any nutrient loads and thus poses a risk of eutrophication for waterbodies. The algae biomass obtained 'incidentally' can then be applied to fields instead of mineral fertilizers. In this way the nutrients are to be returned into a cycle instead of ending up in sewage sludge or in waters where they are no longer usable or even harmful to the environment. In recent years, for example, research has been carried out into how much phosphorus algae can absorb under different environmental conditions and whether algae biomass is a complete substitute for mineral fertilizers when growing wheat. The introduction of microalgae into the soil as an organic fertilizer can also help to improve soil quality, as they bring along carbon previously fixed as CO2. The slow breakdown of the cells also means that the nutrients are released more slowly and are not washed out as easily. The exact effects need to be further investigated, especially for different types of wastewater, but we believe that a very good contribution to nutrient cycling is possible.

There is also potential as a technical supplement; the use of microalgae in addition to the usual sewage treatment steps can help to increase efficiency even further, which is particularly desirable when the phosphorus limits in the water are lowered. It is also conceivable to use algae for on-site clarification of, for example, yellow water or grey and rainwater circuits in order to reduce drinking water consumption. In the future, it will be very important to test the standards of the individual aspects of these circuits - how large can or must such installations be in order to work profitably in terms of energy or economy, for example on an office roof? There is still too little data available here - we would therefore like to simplify the technology as much as possible in order to be able to realize more and more installations and make the technology more accessible and suitable for everyday use - and to link it to as many other resources as possible in a meaningful way. This is where digitization will be a great help in making this easier for the user.

What stages of testing or legal classification still need to be taken in order to achieve broad marketing for nutrient recycling?

So far, it is not yet possible to easily reintroduce products obtained from waste or wastewater into the nutrient cycle, except as fertilizer. A regulated quality assurance is of course necessary here, but also a simplification of being able to define valuable substances at all - be it extracts from algae grown on waste water, which are to be further used (for example lutein or DHA/EPA), or the directly obtained biomass. Sample processes need to be established to demonstrate efficiency and safety, and to promote user acceptance; since the investment for this process is quite high, there are unfortunately no complete 'real' production processes based on waste streams yet, except in research projects to build on them. A change is already taking place in this area, which hopefully, within a safe framework, will allow more economically viable options in the coming years - not only for microalgae, but also for other waste streams, be it organic waste, coffee grounds or process water from other production lines. An example of this would be the All-Gas project (Spain), in which vehicles are powered by biogas from algae grown on waste water and thus economically viable. In Germany, also due to the climate, more expensive products than pure biomass for biofuel/gas are needed for economic solutions, also because of the lower production capacity - or the integration in the use of all available resources, i.e. the fullest possible utilization of these. For this reason, funding would be useful as a start-up aid, in order to be able to establish the realization of this resource linkage under real conditions at various levels (household, industrial building, large-scale plant); this should also include communication with people at all levels, via farmers, students, researchers, building owners, sewage plant operators, etc., because it cannot be reduced to 'the algae', but rather to an interaction of all available resources at a specific location. For this purpose, it may be possible and necessary, for example, to use a different wastewater and energy system than the conventional one when planning new settlements, even if the techniques mentioned are already applicable to existing structures, i.e. consideration for sustainable techniques in urban and regional planning is necessary, which in many cases already takes place. It is important to note that there is not the 'one' solution to the resource problem, but that, depending on the location and conditions, a flexible, combined solution will produce the best possible results. For a small unit such as an apartment building this can be an intelligently controlled combination of solar (thermal, PV), water use, biomass treatment and algae production for biomass, clean water and indoor climate through CO2 use. We are in a time in which digitalization makes the self-learning control and optimization of such processes possible - we have to take advantage of this in order to finally take the important steps towards a real recycling economy on all levels. There are already possibilities for improved resource use, also for private households, for the individual areas of energy and water use, even for biomass; a linkage and optimization of these would be relatively easy to achieve with microalgae, towards a bio-economically functional recycling unit. 

The recovered and processed nutrients and clear water streams can be used in a closed loop system for fertilizer production, irrigation of vegetable fields, but also for animal feed or food supplements. How complex is it to close the supply chain after treatment with the help of buyers? Do you have the first successful examples of value creation in a closed cycle chain?

Although there are already many postulated processes, the actual realization of a closed chain is rare (see example in the previous question). Especially in Germany with relatively dynamic weather - this makes it difficult to control and predict the light- and temperature-dependent growth of algae - the realization has so far been limited to research projects, e.g. on a small scale with the biofilm reactor at the Jülich FC, or with flow-through cultures at the Technical University of Central Hesse in cooperation with the Rotenburg wastewater treatment plant; or, as an example of facade utilization, at the BiQ Algae House in Hamburg. However, to my knowledge, the cycle has not yet been permanently closed except for the field, also because the question of the necessary reasonable scale and the associated investment and maintenance costs still needs to be clarified. However, we expect this to happen in the near future, also in order to be able to offer an orientation for the real application. There are more and more inquiries from interested parties, who, for example, want to use empty greenhouses or a swimming pool water purification system in a meaningful way and are open to new applications; this, too, puts us in a positive mood for the next steps.