1

In an anaerobic, or dry-fermentation process, BIOFerm’s biogas plants process organic waste and renewable raw materials to produce biogas, which can then be transformed into power and heat in a combined heat and power unit (CHP).
One of the key advantages of BIOFerm’s patented dry-fermentation process is that most biomass can be used – including, for example, long grass cuttings, which can only be used in the conventional wet fermentation units after extensive preparation as they would otherwise get caught up in the stirring devices in the machinery. The same applies to organic municipal waste: It does not matter if e.g. some plastic bags have remained in the waste material, whereas this would obstruct the process in a wet fermentation unit. Dry fermentation does not require the inputs to be liquefied, so the mechanical engineering is less complex, making the technology less vulnerable to disruptions and therefore easier to operate and maintain. 
The entire process consists of the following operation units (OU):
•    OU 1: Delivery and storage of biomass;
•    OU 2: Fermentation;
•    OU 3: Removal of fermented raw materials;
•    OU 4: Ventilation;
•    OU 5: Utilisation of gas.

2

The dry fermentation plant consists of several fermentation units where the organic waste materials or other biomass are fermented to produce biogas. The modular construction with several units ensures a stable supply of gas to the CHPs, thus improving process stability.
On the ground level, the fermenter hall consists of rectangular ferro-concrete containers (inner dimensions: 7m x 30m), the fermentation units, in which the biomass is fermented. After its extraction from the fermentation units, the biogas is stored on top of the fermentation units. The bacteria mix needed for the fermentation is sprinkled over the biomass through pipes in the ceiling of the units. The fermentation units are gas-proof as any entry of oxygen would render the methane-producing bacteria inactive and biogas would leak.

3

The fermentation is done in a batch process, i.e. before being placed inside the fermenter, the bio waste is mixed with already fermented digestate. The mixture remains in the unit for around four weeks. During this period, the biogas is extracted, condensed and stored on top of the fermentation units until it is burned in the CHPs, located in a separate, sound-proof room. The energy produced can be fed into the grid and, if necessary, also be used for the operator’s own needs. The biogas facility requires around 5% of the heat and 3% of the electricity for ground heating etc.

4

Apart from the mechanical filling and emptying of the containers through a front loader, the entire process is controlled automatically through a computerised control unit. Any disturbances are detected immediately and reported to the operator by phone, fax or sms.
After the fermentation process, the remnants will partly be reused to start the next batch in the fermentation units, as outlined above, and the rest can be used as high-quality fertiliser or can be further composted.