In 2014-2015 Scandinavian Biogas built a new biogas plant in the South part of Stockholm. This means that locally produced biogas increased by at least 50% in Stockholm County. The biogas plant was constructed at Gladö Kvarn’s recycling plant in close cooperation with SRV Återvinning AB. SRV is a recycling company owned by the five municipalities of Huddinge, Haninge, Botkyrka, Salem and Nynäshamn. The biogas plant is one of the most advanced plants in Sweden, and it was the first industrial plant for digesting food waste in Stockholm County.
Food waste is converted to biogas and bio-fertilizer
The biogas plant, which was commissioned just over a year after construction start, is the first industrial plant for digesting food waste in Stockholm County. On an annual base, the plant utilize the energy from 50,000 tonnes of food waste, which is as much as one third of the two million inhabitantsthe living in the Stockholm’s county. The food waste is collected from households, school kitchens, restaurants, the grocery trade and the food industry mainly from municipalities in Stockholm County, but also from other parts of Sweden. The municipalities are responsible for collecting food waste from households and large kitchens, while the grocery trade and the food industry are themselves responsible for collecting the food waste. The food waste is usually collected in a truck or tanker truck and transported directly to Södertörn’s biogas plant. The municipalities have the opportunity to trace the waste to each household and have deviation management systems. Before the food waste is tipped into the biogas plant, it is weighed into a weighing station. In addition, the plant is also processing 15,000 tonnes of organic waste from commerce and industries.
The food waste is collected and then, by pre-treatment and digestion converted to renewable biogas and a nutritive bio-fertilizer. The Södertörn plant has a capacity of 80 GWh biogas which corresponds to 8.8 million liters of petrol or the amount of vehicle fuel consumed by 5 000 privet cars each year. Raw biogas is upgraded, using a Pressure Swing Adsorption (PSA), to CBG and transported offsite.
Supporting local farming
Up to 110 000 tons of liquid bio-fertilizer are produced yearly. This is certified to meet the quality demands of the SPCR 120 regulation for digestate utilisation on arable land issued by Avfall Sverige – The Swedish Waste Management Association. Most of the liquid bio-fertilizer is dewatered to about 15 000 tonnes of fast biomass fertilizer and delivered to agriculture. The water phase is evaporated to about 12 000 tonnes of concentrate per year and used as nitrogen and potassium fertilizer. The condensation water from the evaporator is used as dolution water in the pre-treatment facility, which considerably reduces the consumption of drinking water in the plant.