Drying of liquid digestate

We have developed a process for energy-efficient drying of liquid manure and fermentation residues from both wet and dry fermentation. The ecoDry process is based on the technology of drying with superheated steam. The drying process requires a primary energy source like natural gas or biomass. This is necessary for generating the superheated steam for the drying process and to thermally oxidize, i.e. destroy the odours contained in the drying gas.

Further concept and process information can be found in this document.

The result: A spreadable fertiliser granulate

Digestate from wet fermentation and/or animal manure

In this case the fermentation residues or liquid manure with a dry matter of approx. 4% are concentrated in a vacuum evaporator to a DM of approx. 15%. This equals a 5 times volume reduction.

In a second step, the concentrate is dried in the ecoDry to a low-odour granulate with 94% DM. During this process the volume is further reduced so that a volume reduction of 13 times compared to the starting product is achieved.

At least 60% of the energy required to operate the ecoDry-dryer can be recovered and used for the evaporator. Additional energy sources for the vacuum evaporator can be waste heat from a biogas plant or other.

Digestate from dry fermentation

This process does not require a vacuum evaporator, which results in significantly lower investment costs. The fermentation residues with a dry matter content of approx. 15-21% are dried directly in the ecoDry-dryer to a fertilizer granulate with 94% dry matter. In this process, an 8 times volume reduction is achieved.