Our biogas plant
Where food waste turns into biogas and biofertilizer.
At the our biogas plant at the Gryta Waste Treatment Plant in Västerås we digest organic waste such as food waste from households, restaurants, food production, warehouses and stores, and also grease trap slurry from restaurants and large-scale kitchens. The products from the digestion process of the organic waste are biogas and biofertilizer.
The biogas that’s produced at the biogas plant is then upgraded to vehicle fuel at the upgrading plant and is used as fuel for buses, cars, and garbage trucks. We are also upgrading biogas from the sewage treatment plant in Västerås. Biofertilizer is used by farmers nearby to return the nutrients back to the soil. By utilizing organic waste at the biogas plant, an environmentally friendly cycle of energy and plant nutrients is created.
The plant was started in the summer of 2005 and has been in full operation since 2006. The plant could at that time process about 18 000 tons of food waste a year and, 3 500 tons of grease trap slurry and 1 000 tons of ley crops. After the biogas plant has been upgraded in 2021 it can now process 30 000 tons of food waste and 10 000 tons of grease trap slurry.
Biogas from the Vafabmiljös biogas plant, together with biogas from the sewage treatment plant, is estimated to produce vehicle fuel to the equivalent of about 3,2 million liters of petrol per year (based on 2021 numbers).
Treatment of organic waste
Foodwaste from household the VafabMiljö region (municipalities in Västmanland and also the Heby and Enköping municipalities) are processed in the biogas plant. The system for separation of food waste from households is based on the paper bag model in which food waste is kept in special-purpose paper bags made of wet-strength paper. Food waste from restaurants, is dealt with on the same principle. Also, other organic waste such as the grease trap slurry from restaurants and large-scale kitchens and organic waste from food production, stores and warehouses is processed at the biogas plant.
Oxygen-free digestion process
The food waste and organic waste is mixed with water and then decomposed in an oxygen-free digestion chamber where microorganisms digest the mixture. Biogas consisting mainly of methane is generated in the process. The biogas is used as vehicle fuel.
The material that is left after digestion chamber has high nitrogen content and is used as biofertilizer on arable land.