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MEMBER PRESS RELEASE – The cycle of slurry separation

MEMBER PRESS RELEASE – The cycle of slurry separation
Efficient, Simple, Reliable – the new way of separating manure with the “Sepogant Direkt” press screw separator and the optional ROTORICOS wet shredder

Innovations have always driven economic progress. It is only through continuous development and improvement of what already exists that it is possible to increase operational efficiency. This is true in all sectors – including biogas.

In the biogas industry, the reduction of emissions and the fermentation process, all in a closed cycle, play a decisive role, which is already important in the manure separation process that precedes. But how is it possible to achieve a smooth and emission-free cycle of manure separation embedded in a biogas plant?

An innovative approach to this is the “Sepogant Direkt” separation technology, which is explained in more detail below.

“Sepogant Direkt” press screw separator

The principle of separation has existed for many years. It is possible to de-water liquid manure, fermentation residues or other slurries by means of press screw separation. The liquid element of the substrate is separated from the solid element. This not only reduces the volume of liquid stored in slurry and digestate, but also helps to save on agitation in the storage tanks. It is possible to use the solid part as bedding. However, if this is not desired, the processing of the solid part is associated with additional costs and higher ammonia losses, as well as further emissions. The liquid element, on the other hand, can be spread more flexibly, easily and cheaply on green grounds, for example grassland, cereals, catch crops, etc., with lower ammonia losses. In addition, there are no technical challenges to overcome in the application technique, such as blockages in the distributor head.

In the draft of the TA-Luft known to date, the separation of digestate is only permitted in closed rooms. For this reason, the storage of this solid material must also take place in closed rooms or covered.
There are regular innovations in separation technology, which are intended to meet the ever higher economic and environmental requirements. These include direct separation by the “Sepogant Direkt” separator. This variant of the press screw separator removes substrate from the fermenter or secondary fermenter in order to feed it again with the thickened element and the not yet completely fermented fibrous materials directly after separation. In this way, the material that is not yet fully fermented (fibre >0.75 mm) is returned to the fermenter / secondary fermenter and has time to ferment further – because different feedstocks take different lengths of time to ferment.

Set-up of the “Sepogant Direkt” on a secondary fermenter / digester
1.0 Mounting level
2.0 Base frame consisting of
2.1 Trolley
2.2 Rail for trolley
2.3 Collecting tray
3.0 Filling line TT-PSS-D
4.0 TT-PSS-D consisting of
4.1 Knife-gate valve
4.2 Outlet line for press residue (solid phase)
4.3 Sight glass
5.0 Outlet line for thin fraction (liquid phase)


With the “Sepogant Direkt”, it is no longer necessary to collect the solid element and regularly feed it again via the feed-in technology, as is already successfully implemented in practice. This has the advantage that there are no additional emissions generated outside, as the “Sepogant Direkt” technique is a closed system. In addition, the transport between the place where the separated solid material is located and the fermentation container (e.g. digester) is saved. This results in further emission savings, which would be caused by transport or intermediate storage.
The “Sepogant Direkt” can also be used for difficult input material that causes problems in the fermentation process, such as the accumulation of a large amount of long-fibre material. In this case, it is possible to use the ROTORICOS wet shredder in the system. The mill-like system fibres the problematic materials and shreds them in such a way that a more homogeneous mass is created in the container.

Feedstocks before and after defibration
Screw press separator “Sepogant Direkt” with wet shredder ROTORICOS

The process of repeated feeding saves feedstock. This leads to the entire gas potential of the fed substrates being utilised. In addition, the use of agitators and the agitation times in the fermentation residue store are saved, as the containers contain a homogeneous mass of the same structure, which does not segregate again. The “Sepogant Direkt” makes it possible to implement the existing process efficiently and with labour savings for the operator. Furthermore, the volume of the feedstock is saved during feeding, which results in a lower load (energy and wear) on the feed technology.

The R+I diagram schematically shows the integration of the “Sepogant Direkt” separator into the process sequence of a biogas plant.

R+I diagram of the “Sepogant Direkt” with optional wet shredder ROTORICOS


The ROTORICOS wet shredder, which is optionally available depending on the area of application, can be installed in the feed line to the separator or downstream of the separator for shredding and defibration.
Various sensors, mostly pressure sensors, are used to control and regulate the separator and the associated substrate pumps. A special mounting platform on rollers was developed for serviceability.

The substrate in the fermenter does not become significantly thicker (max. 1 % dry matter) through this method of repeated feeding, as the more homogeneous composition of the substrate here promotes better biology and thus decomposition. In the secondary fermenter, a slight thickening of the digestate takes place, as the press water has already been removed in the previous cycle.

It is possible to achieve a smooth and emission-free cycle of manure separation in a biogas plant by ensuring that the substrate, once in the fermentation cycle, does not leave this cycle at any time. This can be ensured by the separation technology of the “Sepogant Direkt”, as here the separation of the input materials takes place in a closed system and the solid element is not discharged as before, but can be brought directly back into the biogas plant.

Thus, the cycle remains closed even with the manure separation.

For further information:
Robert Ohneberg
Biogastechnik Süd GmbH
Am Schäferhof 2, 88316 Isny
Tel.: +49 7562 97085 40

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