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Plant engineering

The WITTERRA humus plant consists of three main plant components:  

Treatment basin

The ground-level concrete treatment basin with maximum dimensions of 20 x 120 m is open at the front and has side walls up to 1.75 m high.

Aeration and mixing technology

Up to five aeration and mixing screws made of stainless steel, mounted on a two-axis running unit, ensure optimum aeration and mixing in the entire volume of the treatment basin.

Liquid dosing

An eccentric screw pump, which is also located on the barrel unit, draws liquid from a shaft located on the side wall and introduces it into the material bed immediately in front of the screws. 


The organic material introduced is decomposed by aerobic microorganisms in the humus plant. The output product is a nutrient-stable humus that can be used as a fertilizer or peat supplement in the potting soil production. The output has a dry matter content of 45-60 %, depending on the input materials and the process control.


Start-up phase
The liquid residues are fed into the fermenting material once a day. In the same operation, the
material is completely aerated and mixed. This starts the activity of the microorganisms as well as the biological stabilization and the temperature within the material increases.

Biooxidation phase

After only a few days, temperatures above 70˚C are reached, through which the organic material is sanitized. This is also the active phase of the process, in which easily degradable organic components are rapidly decomposed. Due to the high temperature the water evaporates.

Maturation phase
In the last weeks of the process, the material is stabilized and enriched with humus molecules. No more solid or liquid material is added. This last phase is characterized by transformation processes of the organic matter, the maximum expression of which is the formation of humic substances.

Process flow

The humus plant functions as a batch process in which liquid residues are continuously added.

The process sequence can be divided into five steps:


Filling with dry material

The plant is filled with dry carrier material. Depending on the size of the plant, this is done up to a
bulk height of 1.70 m. A description of suitable carrier materials can be found here.


Liquid dosing

The daily dosing of the liquid material takes place directly in front of the aeration screws in order to incorporate the liquid as quickly as possible. Which liquid residues can be used, can be found here


Aeration & mixing

The entire material bed is ventilated and mixed daily in one operation. This is essential for the aerobic degradation processes in the humus plant in order to supply the microorganisms with sufficient oxygen and nutrients.


Humus formation

The humus formation takes place within 8 - 12 weeks under process biological supervision with a subsequent maturation process of 2 - 4 weeks.


Humus extraction

After the cycle is complete, all the material is removed from the system. New material can then be introduced and a new cycle started. Depending on the requirements, the finished humus can be further processed by screening or pelletizing.

Input materials - solid & liquid

Liquid residues

The application possibilities of liquid residues in the WITTERRA humus plant are very wide. For the introduction of liquids into the material bed, they must be pumpable and, depending on their density, should not exceed a dry matter content (DS) of 20%, in some cases even up to 25%. In addition, the liquids should be free of ingredients that may have a biologically inhibitory effect, such as cleaning agents. Ideal liquid input materials are:


  • Farm manure from animal husbandry

  • Fermentation products from agricultural biogas and biomethane plants

  • Fermentation products from industrial biogas plants (food waste, biowaste)

  • Sewage sludge from municipal and industrial wastewater treatment

  • Industrial wastewater, e.g. from food production

Solid structural material

The most important task of the structural material is the storage of oxygen and the provision of a large surface for the microorganisms. The dry matter content of the structural material should normally be above 50%. Suitable structural materials are:

  • Straw

  • Horse, cow, pig manure 

  • Champost

  • Wood chippings

  • Green waste

  • Fresh compost

  • Dried fermentation residues

Starting materials - high quality humus fertilizer

The only raw material of the WITTERRA humus plant is a light and structure-rich humus fertilizer with a dry matter content of above 50%, rich in organic carbon as well as humic and fulvic acid, which can be used as peat substitute in the potting-soil production soil without further additives or as an organic fertilizer. Depending on the requirements, the humus can be sieved or pelletized.

The results of the seedling tests of the Lower Saxony Chamber of Agriculture prove the plant compatibility of our humus fertilizer:

“No visible damage occurred to the bush beans and chinese cabbage plants in any variant and there was no reduction in fresh mass yield. Plant-damaging substances were thus not detectable in the tested proportions of "Sample 2" in the substrate."

The humus fertilizer achieves the same or even better results in terms of fresh mass and germination number than the reference standard peat substrate, as shown in the table below.


Humus custom-made: depending on the process and the input materials, the nutrients in the end product can be controlled to reach in the final product the exact properties that our customers want. If the humus is to be used as a fertilizer, nutrients are added in a targeted manner via the structural material. If the humus is to be used as a peat substitute, the proportion of fibrous and nutrient-poor materials is increased.

Added value

Groundwater protection

Through the humification process, the nutrients of fermentation residues and liquid manure are stored in long-chain humus molecules. This minimizes the leaching into the groundwater, especially of nitrate.

Volume reduction

Liquid residues are turned into a solid humus fertilizer. From 10,000 t of liquid manure, 3,400 t of HUMUS with 50% residual moisture are produced. The continuous supply of liquid effectively relieves the required storage volume.


The humus plant neutralises existing bacteria through the self-generated heat of over 70°C. The humus fertiliser is therefore demonstrably sanitised.

Humus production

Aerobic treatment produces high-quality humus from organic residues, which can be used as plant soil or for soil improvement and stores CO2 in the long term.

Full processing

The humus plant is suitable for the complete processing of liquid residues. All liquids are refined into high-quality humus fertilizer. Excess seepage juices or percolate do not occur with our process.

Green Field

Full treatment






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