Sustainable productivity

Fluidized bed drying system at ARA REGION BERN AG, Berne, Switzerland

Already a leader in environmental sustainability, ara region bern ag (arabern) in Switzerland had an ambitious plan to produce renewable energy. Their plant has used digestion gas for heating processes in the wastewater treatment plant. But a new concept would take the plant’s energy efficiency and environmental sustainability to the next level.

The challenge: 

Produce CO2-neutral energy from waste and wastewater

To accomplish their goals to convert biogas into CO2-neutral biomethane for direct injection into the gas grid, an entirely new sludge drying plant was required to:

  • use 16-bar steam (instead of digestion gas) from the incinerator for sludge drying,
  • dry an annual 38,000 tons of sludge with 29% DS to 90% dry solids content,
  • use the dried product coming from the dryer as a substitiute fossil fuel for the cement industry.

The client had pre-selected a Fluidized Bed Drying System (FDS) on the basis of excellent experience with their existing ANDRITZ SEPARATION fluidized bed dryer plant over the past 13 years. In addition to its proven reliability, the technology would be ideal in achieving the new plant’s goals for high automation, high safety levels guaranteed by inert gas conditions at each stage of operation, and high thermal efficiency using steam condensate.

Our solution: 

A new Fluidized Bed Drying System (FDS)

Working closely together with arabern, ANDRITZ SEPARATION has helped to develop a new turnkey electromechanical system to facilitate the new CO2-neutral operations. The compact process design utilizes closed gas loops to ensure energy-efficient and environmentally friendly operation with minimal amounts of exhaust gas.

The new system is highly automated, requiring only one operator during daytime operations and no operator attendance during nights and weekends. Low maintenance and operating costs are also assured due to the small number of moving parts, which contribute to reduced wear and tear.

Along with the upgraded, steam-powered system design, ANDRITZ SEPARATION was able to improve the previous plant design in cooperation with a team of highly experienced operators, particularly in terms of optimized maintenance conditions and wear resistance.


8.1 million acm of biomethane gas per year

The new steam-heated sludge drying system now makes it possible for more than 8 million acm per year to be upgraded to biomethane and fed directly into the natural gas grid of the city of Berne. 

The biomethane, which has properties similar to those of natural gas, has made it possible to significantly reduce the combined CO2 emissions of the waste incineration and wastewater treatment plants. Additionally, all wastewater sludge is now dried and transferred as sludge granulate for use as a fossil-fuel substitute or as a mineral product for the cement industry.

On top of being able to produce 100% renewable energy from sludge for the city’s gas grid, arabern has also considerably reduced operation costs for sludge drying and disposal. As the sludge market continues to evolve with new technologies and strategies for hydrothermal carbonization, gasification, phosphorous removal, and more, the arabern plant stands as a major milestone in sustainable wastewater system design.

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  • Success story: Fluidized bed drying system at ARA REGION BERN AG PDF : 433 KB