There is no waste in nature. Everything is utilised, transformed, recycled and taken up anew in the circle of life. Biologist and agronomist Christian Ulrichs is convinced that this cycle can be a model for the production of food. At the Albrecht Daniel Thaer-Institute for Agricultural and Horticultural Sciences, he heads the Department of Urban Ecophysiology of Plants where he is working on the research project 'CUBES Circle', researching how production systems can be highly efficient and at the same time sustainable.

Fish, insects and plants – using these three components the researcher Christian Ulrichs is planning a shift in the production of foodstuffs. His concept is aiming for nothing less than "the highest possible resource use efficiency". In order to produce food sustainably, the nutrients are circulated and various production systems linked. "The residual material from one system is a useable resource for the next system," says Ulrichs, explaining his design.

The researchers of the joint project found inspiration for their concept from nature itself: natural food chains are based on plants that convert nutrients and solar energy into biomass. Herbivores such as insects, for instance, use this as their food source and are then eaten themselves by other animals such as fish. Christian Ulrichs and his team want to recreate the steps in this simple food chain. In large fish tanks, schools of Silver Carp and Tilapia swim, fed by the larvae from the neighbouring insect farm, while their excrement is used as nutrient-rich fertiliser for the vegetable crops in the adjoining greenhouses. Each production module for fish, plants and insects is about as big as a shipping container and stackable.

The highlight: in a small space, large quantities of vegetables, fish and insects can be produced with much less fertilizer and lower emissions. The insects, which are a valuable sources of protein, could also be used as sustenance for people. "But the acceptance is still lacking," acknowledges Christian Ulrichs. The insect larvae are therefore primarily used as fish feed, but also in the recycling of leftover nutrients.

The larvae of soldier flies are particularly good candidates to assist in the recycling of leftover materials. "They're not attractive creatures, but they're very efficient," says Christian Ulrichs, praising the inconspicuous, round maggots. "They're good at processing food, very robust, they eat plant leftovers from the greenhouses and all manner of waste." The larvae also happily feed on food waste from restaurants and supermarkets. In Germany alone, 12 million tonnes of food waste end up in the bin each year. With the help of insects, this waste could be repurposed and turned back into valuable foodstuffs.

Currently, the researchers are still testing the individual modules (the so-called 'CUBES') of insect, fish and plant production as separate systems. Each unit is monitored using sensors which measure the different climate parameters, substratum temperature and humidity, and the level of gasses such as CO2, oxygen and ammonium. Even quality parameters such as the colour of the plants and the level of stress hormones in the fish tanks will be collected and analysed. Colleagues at the Technical University Chemnitz, the Technical University Braunschweig, and the Leipniz Institute of Freshwater Ecology and Inland Fisheries are analysing the data and developing algorithms to adjust and optimise the systems. Ultimately, production should be at the highest possible level of output and efficiency – primarily though, it should run automatically. Other research questions address the acceptance and user-friendliness of the facilities. However, the biggest challenge for the researchers at the moment is coordinating the individual modules so that they interlink smoothly. The food for the fish and insects, the exchange of gasses between the systems, the water and air temperatures and the amount of fertiliser are important parameters that control and regulate the system. The flow of materials must be precisely calculated in order to determine the resulting biomass and the required nutrients.

Later, when the researchers have worked all this out, the 'CUBES' will be linked together in a 'CUBES Circle'. In 2021, a 200-square-metre, two-storey pilot facility will be constructed at the Dahlem campus in Berlin. In the years to come, the project will make the leap from theory to practice and will actually produce foodstuffs on a large scale. To do this, the researchers are bringing partners from the food industry on board. The food production facility could be particularly attractive for locations where the ground is not very fertile, where there is limited space, or where other environmental restrictions make food production difficult: in the city, on industrial sites, in desert regions or in densely populated regions. The units are stackable, and can be extended to be any size. "The 'CUBES' could even be transported on ships to crisis areas where crops have been destroyed by floods for instance," explains Christian Ulrichs, describing other possible uses.

Before it gets that far, however, there is still a lot to do for the research team, who already have a number of ideas about how to expand and increase the value of this system. Experiments with specific cultures are already in planning. Duckweed, for example, could also be grown as a vitamin-rich leafy vegetable using the excrement from the insect farm. The controlled conditions of the 'CUBES' would make them ideal for growing medical cannabis, and certain insects, which provide valuable oils to the cosmetic industry, and Water Celery, which does not cause allergic reactions, unlike regular celery, would also thrive in the plant modules.

The focus of the 'CUBES Circle' project, however, is the production of foodstuffs on a large scale. "The agricultural systems of the future need to be economically viable and still more sustainable than anything we have had up until now," stresses Christian Ulrichs. He is convinced that the 'CUBES' concept meets precisely these requirements. The water, energy, fertiliser and emission savings lie in the "higher double-digit-percentage range" he explains. The greenhouses are designed such that water condensation can be caught and recirculated. Using a shelving system, lettuce or peppers could be produced in a very space-efficient way, and carbon dioxide, a respiratory bi-product occurring in the insect farms and fish tanks, is channelled to the plant crops to encourage stronger growth. Everything is aimed at efficiency, closed-loop systems, minimal waste and low emissions. "It's a very intense production system," says Ulrichs. "But intense in a positive way."

• -Study by the Thünen Institute on food waste
• -Water Celery as an allergen-free alternative
• -CUBES Circle on Instagram
• -CUBES Circleon ResearchGate