Digestate evaporation

The Vapogant digestate evaporator treats the digestate of the biogas plant to produce a usable, concentrated fertiliser with reduced water content.
We remove most of the water from the digestate through vacuum evaporation using waste heat from the CHPS. At the same time, volatile nitrogen is bound so that any emissions during spreading will be minimised, making the nitrogen available as ammonium sulphate solution (ASS).
The goal is to use the available waste heat to thicken or enhance 100 % of the digestate produced in the biogas plant. This is achieved with a very high evaporation rate of 2.5 litres per kilowatt of thermal output. At 500 kW plant capacity, this is equivalent to a volume reduction of about 10,000 m³ per year.
The plant is available in a module size of 400 kW or 500 kW.

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Digestate evaporation

Waste heat utilisation

  • Automatically controlled 100 % utilisation of heat
  • Multiple use (multi-stage) through vacuum system
  • Also at high outside temperatures
  • Heat recovery:
    • 1. Evaporation
    • 2. Digester heating
  • Reliable additional revenue through CHP if available
Digestate evaporation

Digestate storage capacity

  • Reduction in digestate volume by up to 70 %/ annual volume, i.e. 10,000 m³
  • Enormous thickening of liquid phase to up to 20 % DM
  • Low space requirement of 100 m² only
  • No need for construction of additional digestate storage capacity
  • No Hazardous Incident Ordinance requirements
  • Construction of digestate store has most often no additional benefit
Digestate evaporation

Problem of 170 kg N limit

  • In-house production of ASS
  • Use of nitrogen fertiliser exceeding 170 kg N limit possible
  • ASS is a valuable commercial fertiliser
  • Very low N losses during storage and spreading
  • Targeted sale of nutrients is no cost factor, but additional revenue
Digestate evaporation


  • 100 % closed system
  • Full condensate treatment
  • No odours
  • No exhaust gases
  • No noise (60 dB at 10 m)
  • No particulate matter
  • Vacuum pump recirculates exhaust gas to gas system of biogas plant or activated carbon filter
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How does the Vapogant work?


Use the digestate from your biogas plant to produce a high-quality mineral fertiliser! We explain how the Vapogant optimally processes and refines your digestate.

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Vapogant digestate evaporation cycle

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Technical process of Vapogant digestate evaporation

Use of the ammonium sulphate solution (ASS) obtained

The ammonium sulphate produced by the digestate evaporation system can be used further as customers see fit:

Digestate evaporation

For your operation

The ASS is stored in separate storage tanks (e.g. 100 m³ horizontal) to be spread subsequently using a sprayer or the CULTAN method. – Ideal to supply plants with the amount of nitrogen they need.

For commercial use

The ASS as a mineral fertiliser can be resold as a valuable commercial fertiliser.

Distillate use

There are different options to use the distillate for operations: Storing the water to be used as washing water for stables and areas, as thinning water for pesticides and liquid fertilisers, etc.

Using the distillate for operation purposes

There are different options to use the distillate for operations: Storing the water to be used as washing water for stables and areas, as thinning water for pesticides and liquid fertilisers, etc.

Evaporation of the distillate through the wet cooling tower

As a cooling unit is needed to operate the plant, part of the water may also be evaporated continuously through a cooling tower. Additionally, the cooled water is used as a cooling medium.

Indirect and direct distillate introduction

The water is introduced continuously to a receiving stream, combined with an upstream distillate processing module if necessary, or it can be allowed to drain.


The map shows our reference customers and all Vapogant systems in operation. If you would like to visit a facility near you, we will be glad to schedule an appointment for you. Just call us!



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