Proweps envirotec – with the Diefenbacher  Company as main contractor –  was engaged in an innovative project to modernize and extend the existing anaerobic digestion plant of VafabMiljö in Västeras, Sweden. The complete 3D-engineering, project management and supervision of construction and commissioning was Proweps scope.

In the frame of the project, VafabMiljö modernised the existing 15 year old biogas plant and upgraded it with a second line. The capacity of the entire plant is expanded to 40,000 t of household waste, food waste and other liquid organic waste from restaurants, food production etc. The modern technology increased operational reliability and efficiency – especially the biogas yield between  by 10 % – while methane losses and energy consumption are reduced. In a new additional gas upgrading plant, raw gas is also processed into vehicle gas with a total capacity of 2.7 million cubic meters.

The high quality liquid fermentation residues (digestate) produced for agriculture meet the requirements of the national Swedish SPCR120 quality assurance scheme.  They are used and spreaded by farmers in the region as a liquide fertilser.

Many new technical innovations are being implemented in the project. In addition it is a very good example how existing plants can be modernised. Therefore the project was co-financed by the Swedish Environmental Protection Agency through the “Klimatklivet” fund.

Two interesting videos below show a technical round tour and the public opening with statements of experts and politians.

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Picture: Effective and modern biogas plant in Västeras, Sweden – Source Vafab

New Biogas plant Västeras, Sweden


After nearly 15 years of operation it was time for remodelling the VafabMiljö biogas plant in Västeras. The reconstruction and enlargement of the new plant was finished in 2021.

The new plant has the capacity for 40.000 tonnes of organic household and commercial waste annually which are converted into biogas and biofertilizers.

  1. The new reception building can receive 60-100 tonnes of food waste per day by trucks.
  2. The waste falls into the buffer container and feeds the pre-treatment machine which can process 9 tonnes an hour.
  3. Here the food waste is mixed with process water to create plumpable slurry.
  4. All controlled and monitored in the control room.
  5. For the sand separator the slurry is pumped into containers, where it is swirled around at high speed in order to separate the heavy particles.
  6. After that the slurry goes to new suspension tank (900 cbm)
  7. and from there to the new digester tank where biogas is produced.- about 10 % more biogas compared to the old system.
  8. The digestate becomes a liquid biofertilizer which is stored biofertilizer tank (about 80 t/d), which we later transport to farmers for spreading on their fields.
  9. In the 2 small new sanitization tanks the slurry is heat up to 55 C for about ten hours which saves energy compared to the old plant with sanitization of 70° C for an hour.
  10. The new biogas upgrading system processes about 700 cubic metres of gas an hour. The use of a scrubber results in vehicle-grade biogas with about 97 % methane content.
  11. The plant provides about 5.200 cubic metres per day to gas stations in Västeras, Enköping, Fagersta and Sala for public use and for bus depots.

All of it aims to link together city and country in a cycle of nutrients and energy in the form of gas, to our city buses, and nutrient rich fertilizer for our farmers.


VIDEO – Technical Round Tour of the New VafabMiljö Biogas Plant 2021 (Swedish/English subtitles)




“It is obvious for the region that we need to focus on Climate issues because we see what is happening in the world with flooding and tornados even here in Sweden.

It is what Vafab does and so we never felt more right to open this type of new biogas facility which is now ready to process a lot of organic waste and food waste bags from households. It includes a new gas upgrading system which transforms biogas into gas which can be used as fuel for vehicles.

It is an important investment and the new plants works very well and thus makes us happy “remarks Carina Färm, Association Director of VafabMiljö.


VIDEO – Opening of the New VafabMiljö Biogas Plant 2021 (Swedish/English subtitles):