In the anaerobic fermentation module, the processed biomasses are degraded by microorganisms in a controlled process. In this process, part of the contained organic matter is converted into biogas, a mixture of mainly methane and carbon dioxide. Two reactor lines are available for this purpose, which differ in their first process stage. One line has a continuously stirred tank reactor as the first process stage, as it is common in agricultural applications, for example. The second reactor line, in contrast, uses a plug flow reactor at this point, as is widely used in the treatment of organic waste. Common to both process lines is that the second and third process stages are each designed as continously stirred tank reactors. This allows a direct comparison of the most common reactor systems. Here, the methane yield over the process stages can be assessed as a function of varying process parameters.

In the methanation module, the biogas from the two digesters is mixed with externally supplied hydrogen without separating the methane. In the temperature-controlled tubular reactor, carbon dioxide from the biogas reacts with hydrogen on a catalyst to form methane and water. After the water is separated in a condensate trap, a product gas is produced with a methane content almost twice that of biogas. On approx. 500 ml of catalyst and at a process pressure of 20 bar(a), 2.5 m³/d of biogas with approx. 50 vol% methane content is converted into approx. 2.47 m³/d of synthesis product with > 95 vol% methane content. To ensure that the product gas is suitable as a fuel, unreacted residual carbon dioxide can be removed by gas scrubbing.

In the digestate treatment module, the portion of biomass that has not been fermented into biogas is treated to produce dischargeable water, a solid organic farm fertilizer rich in nitrogen and phosphorus, and a liquid inorganic farm fertilizer rich in nitrogen and potassium. In addition, a recirculate can be provided from the liquid phase of the digestate for mixing in the biogas process. The first step of digestate treatment consists of separating the solid phase from the liquid phase by means of a press screw separator and decanter centrifuge or chamber filter press with the addition of flocculants. For further treatment or concentration of the liquid phase, the membrane technologies ultrafiltration and reverse osmosis are available. With the separation cascade, an average of 0.1 - 0.5 m³ of digestate can be processed per day with the aim of achieving a volume reduction of at least 50%. The quantity and quality of the recovered nutrients or farm manure depends on the biomass used and the process conditions in the anaerobic fermentation. During processing, all relevant process parameters are recorded for monitoring the separation processes and for determining mass and energy balances.

In the pilot plant context, the module "Hydrothermal Processes" (HTP) covers processes for the digestion, treatment or upgrading of biomasses and residual materials, in particular those with a high water content, under elevated pressure and temperature. The processes typically run at temperatures of 150-280 °C and pressures of about 5-65 bar for between thirty minutes to a few hours. Part of the pilot plant is a 0.5m³ reactor, which can be operated up to 240°C and 39bar. This is used in the lower temperature and residence time range for the pre-treatment of difficult to access biomasses for fermentation. In the course of digestate treatment, higher temperature and pressure levels can be operated in the same plant technology in order to convert aqueous digestate into so-called hydrocarbon as well as to effect a shift of nutrients between the aqueous and solid phases. Taking phosphorus as an example, the portion bound in the solid phase can be transferred to the liquid phase and thus made accessible so that it can be recovered in downstream processes via a precipitation reaction.