In the biogas process the used raw materials are being decomposed step by step into simpler compounds using a multistage microbiological process. The strictly anaerobic living methane bacteria are placed at the end of the decomposition process. The methane is a left over from their metabolism as a waste material. The first two stages pre-digest and acidification are usually often described as hydrolysis. These stages need a different milieu as the production of biogas. Therefore, there are often failures in single-stage biogas plants.

During the acidification period and the use of extremely well digestible substrates acids are increasingly produced under anaerobic conditions which are difficult to use for the methane bacteria, build up in the digester and regularly cause process instabilities.

The usage of fibrous materials, which can barely or only be decomposed within long retention times under anaerobic conditions, is barely possible in existing biogas plants. For new plants huge digester volumes are required which cannot be operated economically.

With an upstream aerobic preliminary stage of digestion the mentioned problems can be eliminated.

The pre-digested substrate (hydrolyzate) is optimal prepared for the methane bacteria. They can utilize it immediately. Thereby the biogas production in the digester is controllable. This allows varying the biogas production from a constant maximum to the flexibilisation to reach a methane content which is adapted to the current needs that have to be covered.

The methane content of the biogas is increased by 5-10% compared to the digestion without a preliminary hydrolysis. This essential decreases the effort of the production of bio-methane.

The fermenting liquid in the digester is considerably better stir able, which makes it possible to use fibrous substrates and the mixture in the digesters are still easy to be mixed.

The aerobic pre-digestion of substrates for biogas plants is used in two system variations:

  1. Micro-aerobic pre-digestion of easily acidify able substrates for increase of the amount of acidic acid in the hydrolysate. That leads to a stabilisation of the biogas process.
  2. Semi-aerobic pre-digestion for the microbiological pre-decomposition of the hardly accessible parts, especially of the fibres in the substrates. Thereby the gas yield is being increased and the use of fibrous substrates is made more economical.

The aerobic pre-digestion-stage is being adapted to the planned use of materials and to the needs of the customer, further it will be technically laid out and biologically commissioned by Bionova Biogas GmbH. Our qualified and long-term experienced partners in planning and construction of biogas plants can assure high quality and technical functioning of the implementation of the pre-digestion-stages, their integration into existing biogas plants or the erection of complete biogas plants.