A new anaerobic digestion biogas plant for green waste is to be built in Tägerwilen, Switzerland. Renergon International AG, Lengwil, which is in charge of the project, starts construction this year. As early as 2019, the plant will supply biomethane to the Kreuzlingen grid and produce high-quality fertilizer.

“The realization of our new solid anaerobic digestion plant is a prime example for Switzerland”, explains Renergon President Karl-Heinz Restle. The plant concept ensures that green waste and biogenic residues are used to generate energy before they are recycled. This follows the guidelines of the Thurgau biomass concept. A major advantage of the plant is that it produces biogas, which is then processed into biomethane and fed into the local gas network of the Swiss city Kreuzlingen. This means that the biogas is produced from green waste and that the city of Kreuzlingen is one of the first municipalities in Switzerland to be able to offer 100 percent of its biomethane from its own biogas, emphasizes Restle. Once all the necessary contracts have been signed, the way is clear for the successful conclusion of the financing round. The building permit is ready. The biogas plant developed by Renergon is based on solid fermentation technology and consists mainly of garage-like fermenter boxes and a percolate tank. In a two-phase process, known as “Renergon Simultaneous Digestion” (RSD), biogas is formed from soluble metabolites. This technology has significant advantages over conventional liquid plants. It ensures high process stability. “The digestion process is stable and low-odor, and the digestion residues can ultimately be used as valuable organic fertilizers with high nutrient availability,” says Restle, underlining the circulatory concept. The plant in Tägerwilen should thus also become an example for international markets, promises Restle. Renergon’s solid digestion technology has already met with great interest in Indonesia, India, and China.

How does an anaerobic digestion plant work?

The basic principle of a biogas plant (anaerobic digester) is simple. Renewable organic materials from agriculture, animal manure, green cut, biowaste collections, residues from the food and agro-industry, are being used as input materials, so-called feedstocks.

In airtight fermentation boxes – the so-called digesters – a fermentation process is being stimulated and produces biogas using bacteria. The bacteria are similar to those that can be found in the digestive tract of a cow. The main products of anaerobic digestion process are is being used for production of electricity and heat, or biomethan usage (grid feed-in, CNG for mobility). Read more.