Gasum uses an annual total of around 200,000 tonnes of sewage sludge in biogas and fertilizer production. The company currently processes around a quarter of the volume of sewage sludge from Finnish municipal systems. Sewage sludge is an important feedstock for biogas and recycled nutrients. The study coordinated by Natural Resources Institute Finland (Luke) reinforces the company’s view that sewage sludge is safe to use in biogas and fertilizer production.

- The new study coordinated by Natural Resources Institute Finland proves that cereals fertilized with sewage sludge are free from contaminants. Contaminants are not taken up by cereals. These findings reinforce our view and support the authorization by Finnish Food Safety Authority (Evira) for the fertilizer use of digestates. The use of sewage sludge-based digestates is not prohibited. They are always carefully sanitized to destroy any pathogens. For example, in Sweden there is the Revaq certification system for sewage sludge to ensure the quality of recycled fertilizers, which has improved the quality of fertilizer use of nutrients produced from sludge. We are continuously exploring new processing solutions and uses for digestates, says Ari Suomilammi, Director, Biogas Production and Sourcing, from Gasum.

Gasum’s network of several plants enables the centralization of the various types of biomass fractions to specific biogas plants. In cooperation with various actors, Gasum is expanding the opportunities for the utilization of digestate in its production network. Gasum produces biogas from sewage sludge particularly for use as a road transport fuel. The value of energy found in biowaste and sewage sludge is maximized in road fuel use, but it can also be used in heat and electricity production, industry and homes. Fertilizer products are created as biogas by-products nationwide at seven industrial-scale biogas plants in Finland at an annual total of around 500,000 tonnes and at five biogas plants in Sweden at an annual total exceeding 400,000 tonnes.

Gasum will continue to use sewage sludge in biogas and recycled nutrients production in the future, too. The circular economy targets set by the EU provide increasing steering towards ways of processing sludge and biowaste where the benefits obtained from side streams are fully utilized. According to these targets, 65% of municipal waste must be recycled by 2030. The current level in Finland averages 30–35%.

Fact box:

•Gasum is the leading processer of biodegradable waste and supplier of biogas in the Nordic countries. Gasum processes an annual total of 800,000 tonnes biomass and produces an annual total of around 650 GWh of biogas at its twelve biogas plants.

•Gasum produces fertilizer products nationwide at its seven industrial-scale biogas plants in Finland at an annual total of around 500,000 tonnes and at five biogas plants in Sweden at an annual total exceeding 400,000 tonnes.

•Biogas production creates fertilizer products for agriculture and gardening soil production as well as nutrient concentrates (such as nitrogen and phosphorus concentrates containing organic carbon) used in agriculture and industry.

•Other organic nutrient products such as nitrogen nutrients containing ammoniacal nitrogen and water are used in industrial applications such as flue gas cleaning at power plants. Demand for organic nutrients is evolving rapidly in a variety of industrial sectors.

•Gasum’s Finnish biogas plants are located in Huittinen, Honkajoki, Kuopio, Oulu, Riihimäki, Turku and Vehmaa. Gasum also produces biogas with its partners in Espoo, Kouvola and Lahti. In Sweden Gasum has biogas plants in Jordberga, Katrineholm, Lidköping and Örebro as well as a majority shareholding in a production plant located in Västerås. In addition, Gasum has a 50% shareholding in Vadsbo Biogas in Sweden.

www.gasum.com