Collection campaign at the CMT trade fair: Urine for bio-concrete research

Cement production is one of the most emission-intensive industrial processes. Scientists in Stuttgart are therefore conducting research into a new, sustainable mineral building material: bio-concrete. To produce it, they use a raw material that has been largely overlooked until now - human urine. Campers staying at the motorhome parking area at Messe Stuttgart during the CMT tourism trade fair from January 17 to 25 can support the research project by donating urine from their separation toilets. Messe Stuttgart, the separation toilet manufacturer Arwinger, and the compost toilet rental company Kompotoi are collaborating with the University of Stuttgart on this collection campaign.

Scientists at the University of Stuttgart are researching a novel building material – bio-concrete. This is produced using biomineralization. In this process, living organisms produce inorganic material through chemical reactions. The material can potentially be produced completely from waste materials in a CO₂-neutral manner.

The biomineralization process developed by the Stuttgart team has one distinctive feature: It is based on human urine – a raw material that is abundant but has been overlooked until now. “The samples produced so far show promising material properties for certain areas of application in building construction,” says Professor Lucio Blandini, head of the Institute for Lightweight Structures and Constructional Design (ILEK) at the University of Stuttgart. The project team has produced test specimens that achieve compressive strengths of over 60 MPa – significantly higher than in all previously published studies on biomineralization. This means that even urine can be used to produce high-strength building blocks. However, according to Prof. Blandini, the aim of the research is not to completely replace conventional concrete: “We see the building material more as an intelligent addition for selected applications.”

The biomineralization process requires large amounts of urine, approximately 26,000 liters per cubic meter of bio-concrete. To enable the team to manufacture and test larger component formats in the future, a large-scale urine collection campaign is now being launched for the first time. This is supported by the sustainable toilet system companies Arwinger and Kompotoi, as well as Messe Stuttgart.

The CMT tourism trade fair will be held at Messe Stuttgart from January 17 to 25, 2026. During the trade fair, numerous campers are expected at the motorhome parking area at Messe Stuttgart. Campers with separation toilets are invited to donate the contents of their urine collection containers for bio-concrete research. Urine donations can be handed in directly at the parking space. The companies Arwinger and Kompotoi provide a special collection container for this purpose and organize transport.

"As a manufacturer of separation toilets, the sensible use of resources for a functioning circular economy is particularly important to us. As a trained concrete builder, I am excited about the idea of researching urine as a raw material for the production of sustainable building materials. I am delighted that we were able to initiate the collection of urine at CMT 2026, thereby supporting the researchers at the University of Stuttgart in their groundbreaking project," says Sven Mahn, Managing Director of Arwinger.

“The basic idea behind our composting toilets is that human waste can be used as fertilizer,” says Kompotoi co-founder Jojo Casanova. "The fact that this can even be used to produce organic concrete was a real eye-opener for us too. It shows how much potential there is in this material flow, which we have previously thought of almost exclusively in terms of a linear system that ends with disposal. That has to change, and it can change. Our excretions can do far more than we give them credit for in the modern world. The exciting thing is that occasions and places where lots of people come together – whether at events or in city centers – suddenly take on an additional dimension of resource creation."

Roland Bleinroth, Managing Director of Messe Stuttgart, comments: "Sustainability and climate protection are particularly important to us at Messe Stuttgart. For years, we have been dedicated to the responsible use of resources and to developing innovative solutions that support a sustainable future through numerous in-house projects. It quickly became clear to us that we wanted to support the bio-concrete research through this year's campaign at CMT in order to work with our partners and the scientific community to identify new ways of achieving a climate-friendly circular economy. We are delighted to be able to contribute to making sustainable developments such as these visible and tangible."

During the CMT, the research team also aims to provide information about biomineralization and bio-concrete. Daniele Funaro from the Institute of Microbiology and Axel Steffens from the Institute for Sanitary Engineering, Water Quality and Solid Waste Management at the University of Stuttgart will be available to talk to at the Arwinger stand (Hall 8 / Stand D03) throughout the trade fair. They will, for example, explain in detail how the biomineralization process works: The researchers add a bacteria-containing powder to sand as the base material, pour the mixture into a mold, and then flush it with calcium-enriched urine over a period of three days. The bacteria cause the urea contained in the urine to be converted into carbonate. The calcium present causes crystals of calcium carbonate (lime) to grow. The sand mixture solidifies into bio-concrete, a solid material that is chemically similar to natural sand-lime brick. Depending on the formwork, elements can be produced in different shapes and sizes, currently with a depth of up to 15 centimeters.

About the University of Stuttgart’s “SimBioZe” project
Biomineralization research is part of the “SimBioZe” project, which combines the expertise of three institutes at the University of Stuttgart: the Institute for Lightweight Structures and Constructional Design (ILEK), Institute of Microbiology (IMB), and the Institute for Sanitary Engineering, Water Quality and Solid Waste Management (ISWA). The Center for Organic Farming at the University of Hohenheim is also involved. Cooperation with industry partners such as Stuttgart Airport is also planned. In addition to biomineralization, the project also focuses on integrating bioconcrete into a circular value chain: The project demonstrates how urine can be collected from wastewater streams and processed for use as a raw material in bio-concrete production. At the same time, the team is investigating how secondary raw materials can be recovered in the process, for example for the production of fertilizers. The project is funded by the Baden-Württemberg Ministry of Science, Research, and the Arts.

About CMT
CMT is the world's largest public exhibition for tourism and leisure. Every year, numerous national and international travel destinations are presented in Stuttgart. It is the most important trade show for new products in the camping and caravanning industry at the beginning of the year. Four subsidiary trade fairs are taking place at the same time: Bicycle & Hiking Travel, Cruise & Ship Travel, Golf & Wellness Travel, and DIY Conversion. CMT also hosts around 600 supporting events under one roof and is simultaneously a trade, public, political, and media event. At CMT 2025, Messe Stuttgart welcomed around 260,000 visitors. A total of 1,570 exhibiting companies showcased their latest products and tourist highlights across 125,000 square meters in ten halls. The next CMT will take place from January 17 to 25, 2026, at Messe Stuttgart.

About Arwinger GmbH & Co. KG
Arwinger is a Hamburg-based start-up that was founded in spring 2021 with the invention of the cassette separation toilet. The company develops and manufactures conversion kits and replacement models for converting chemical cassette toilets permanently installed in camping vehicles into separation toilets with cassettes. Arwinger offers cassette separation toilet kits for all standard Thetford chemical toilets. Since July 2025, the company has had an exclusive strategic partnership with Dometic. Dometic cassette separation toilet models were developed jointly.

About Kompotoi
Kompotoi develops, rents, designs, and sells eco-friendly composting toilets. The toilets not only look good, they are completely odor-free and particularly environmentally friendly. Kompotoi does not use any chemical additives, conserves water, and turns human waste into a soil improver. In this way, Kompotoi closes an important natural cycle. Kompotoi designs facilities for public areas, sells toilet solutions for garden sheds, and offers efficient and ecological sanitation solutions for events and festivals. The company is currently located in the following cities in Germany: Munich, Darmstadt, Cologne/Bonn, and Hamburg.

Interview requests: Please contact the University of Stuttgart Press Office in advance to arrange an appointment. For last-minute press inquiries during the opening weekend, please contact the project staff on site at Hall 8 / Booth D03: Daniele Funaro / Axel Steffens, Tel: +49 711 685-65436
Accreditation for press representatives: To access the CMT trade fair, please register online: Accreditation | CMT