Low-temperature fermentation of poultry manure

A substrate that often causes problems with fermentation is poultry manure. The high nitrogen content leads to biological inhibition. In particular, ammonia (NH3) is toxic to the bacteria above a certain concentration. Apart from this, poultry manure contains contaminants such as sand, which present enormous technical challenges.

Nevertheless, this substrate has considerable potential for biogas production.

As a byproduct of the growing worldwide production of poultry meat and eggs, this waste material presents increasing problems. The poultry manure is often stored inappropriately, leading to dangerous pollution of the groundwater and considerable climate damage through methane emissions.

It therefore makes sense to process poultry manure anaerobically in a biogas plant, especially as it is very energy-rich with a gas yield of around 500 m³/toDM (oDM = organic dry matter) So how can the above-mentioned problems in the fermentation of poultry manure be solved?

Biological nitrogen inhibition

Both ammonium (NH4) and ammonia (NH3) inhibit the bacteria in the fermenter, whereby ammonia is far more toxic and is therefore the decisive factor for the inhibition.

The two chemicals exist in a temperature-dependent balance with each other. At lower temperatures there is more ammonium and less of the toxic ammonia present. This phenomenon is the basis for our Tlow-process. It enables us to achieve a high total nitrogen content combined with low toxicity. The process works at temperatures from 25 to 30 °C.

Inorganic contaminants

Inorganic impurities (such as sand) form sediments at the bottom of the fermenter during the fermentation process. After a short time, considerable layers of sediment form in the fermenter. To prevent this, AEV has developed a patented system for removing these contaminants.

There is a further problem with the separation of the fermentation residue because in conventional separators the abrasive characteristics of the sand lead to enormous costs caused by wear. For this reason, we use special low-wear separators with a long lifespan.

Das gesamte Tlow-Verfahren

  • Thinning of the dry poultry manure using denitrogenized recirculate until it is stirrable
  • Psychrophilic fermentation (25 -30°C)
  • Removal of contaminants from the fermenter
  • Separation of the fermentation residue into solids and the liquid component (recirculate)
  • Elimination of nitrogen from the recirculate in a purification plant

Convincing advantages:

  • Stable biochemical process
  • Very low energy requirement
  • Low investment costs
  • Manageable personnel and operating costs
  • No high qualification of the personnel is necessary
  • No requirement for chemicals
  • No use of fresh water
  • Problem-free changeover to any solid or liquid substrate possible
  • Sustainability and climate protection
  • No liquid fermentation residue, only solid residue
  • We achieve this without any complex ultrafiltration, reverse osmosis or stripping process.

With this patented Tlow process we have made the initial breakthrough in the mono‑fermentation of poultry manure.