With the purely anaerobic technology, most of the organic components found in wastewater can be converted into biogas. Up to now, we have been able to produce 40 to 60 liters of biogas per resident and day while conventional wastewater purification by sludge digestion yields approx. 25 liters of biogas per person and day. The energy content of the biogas produced when wastewater is purified anaerobically is more than 100 kWh per resident and year. If one considers that approx. 30 kWh of electric energy is needed per resident and year to run a large treatment plant together with the same amount again of thermic energy, then the gain of 100 kWh per resident and year obtained with anaerobic technology proves that such a plant could at least be run independent of exterior energy sources.
The present pilot plant in Knittlingen, built for demonstration purposes only, is too small to produce the amounts of biogas needed to run conventional systems e.g. in a combined heat and power plant or with a Stirling engine. However, burning puts it to good use by providing thermic energy for the wastewater purification process.