The digester is the heart of every digestion plant. The decomposition processes of the organic matter take place in it. 

The biomass used is decomposed into biogas and fermentation residues in an anaerobic process involving several steps. A basic distinction is made between high and flat fermenters.

farmatic is a significant technology leader in digester construction. Our fermenters are characterised by optimally implemented process techniques, the use of quality components and perfectly matched expansion options. They can be exported worldwide. The modular segmental design enables the lowest transport costs with maximum flexibility. In addition, our digesters are suitable for a wide range of organic substrates.

High fermenters

High fermenters (so-called continuous-stirred-tank-reactors – CSTR) are characterised by a particularly low energy requirement and the innovative concept of the central agitator. At the same time, they convince through higher efficiency of gas production compared to flat fermenters.

High-rate fermenters can be designed to process liquid manure and energy crops, but also to utilise organic residues, waste from the food industry or organically contaminated process water from breweries and ethanol factories. In modified versions, they are used as digestion towers in wastewater treatment plants. They are optimally suited for both mesophilic and thermophilic operation. The complete mixing of the digester ensures a biologically optimal environment and a maximum degree of utilisation of the gas formation potential.

Our high fermenters are based on specially coated farmatic steel tanks. They are extremely resistant to corrosion and abrasion and have excellent static properties. Highly resistant stainless steel plates are also used in the gas chamber.

High fermenters stand for the significant reduction of intrinsic energy with increased gas production at the same time. Our intelligent energy management and the efficiency of our central agitators guarantee maximum economic efficiency.

The high fermenters consist of

  • a steel tank in bolted segmental construction with enamel or industrial powder coating and tank insulation with weather protection cladding in RAL colours
  • Connection flanges (can be positioned as required)
  • Pressure safety device (optional flame arrester and bursting disc)
  • Gas outlet (optional gas line)
  • Manhole, sight glass unit (optionally with lighting, flushing device, camera monitoring)
  • Central agitator
  • Stainless steel roof (optionally insulated)
  • Ladders/platforms (optionally with spiral staircase or stair tower)
  • Heat exchanger in black or stainless steel (optionally with pipe connection)

The high-level fermenters are assembled without complex scaffolding or crane work. First, a closed ring segment is created. The finished ring segments are lifted onto the foundation by means of a lifting spindle system and the next segment ring is placed underneath. This makes extremely short assembly times possible.

The fermenters can also be erected in hybrid construction. The farmatic steel system is placed on top of the 1concrete base part, which is manufactured on site. The system includes the complete roof construction with all necessary connections and expansion options.

The self-supporting, gas-tight stainless steel roof perfectly absorbs the static and dynamic loads of the central agitator. If required, the roof can also be fully insulated.

Flat fermenter

Due to the integrated gas storage, flat fermenters are a cost-effective solution for fermenter sizes up to 6,000 m³. In our biogas plants, this type of tank is regularly used as a combined storage tank for fermentation residues and biogas.

Flat fermenters consist of an insulated cylindrical corrosion-resistant steel tank. Due to the high aggressiveness of the hydrogen sulphide dissolved in the biogas, the tank shell in the gas chamber is made of a special enamel coating or stainless steel.

The flat fermenters consist of

  • a double-membrane gas storage tank with supporting air blower and sight glass in the outer membrane
  • a slow-running paddle agitator with high circulation capacity at low energy consumption and a further side agitator with external drive
  • an access ladder with a working platform and, if necessary, catwalks.

The fermenter is closed off by a supporting air roof construction with integrated gas storage. A stainless steel central support carries the construction. The inner membrane is made of polyethylene fabric with PVC/PU coating on both sides.

The outer membrane is made of polyester fabric with PVC coating, painted and flame retardant. The outer membrane or the supporting air roof is kept at the necessary pressure by a radial fan.