The work of establishing a biogas plant in Västerås, the "Växtkraft-plant", for the treatment of source separated household waste, ley crops, and other suitable organic waste, has been in progress for several years. Växtkraft is Swedish for "growth power". An agreement in principle between VafabMiljö (the Solid-Waste Company of Västmanland), LRF (the National Federation of Swedish Farmers) and Mälarenergi, regarding the proprietorship and operation of the plant, constituted the basis for the work. The objectives are to produce a thoroughly researched basis for the decision on the building of the Växtkraft-plant. Biological household waste and ley crop is co-digested in an energy effective anaerobic process. The gas is cleaned and used in public transport buses and private cars in Västerås. The digestate is used as organic fertilizer by the local farmers.
The plant produces biogas equivalent to 15 000 MWh for vehicle fuel. With additional gas from the sewage treatment plant (8 000 MWh) 40 city buses, 20 cleaning vehicles and 500 cars will be supported with fuel. The gas that is not sold as vehicle fuel is used for CHP production.
The gas replaces about 2.3 million litres of petrol and thereby reduces a lot of emissions € mostly carbon dioxide by 3 450 ton per year. The production of biogas will generate fertiliser containing 150 ton nitrogen, 30 ton phosphorous and 90 ton potassium and has been approved by the food industry for use in grain crop. The fertiliser is improved due to the digestion and the nutrition is easier for the plants to take up.
Contribution to Sustainable Development:
The biogas production plant contributes to sustainable development in many different areas. The project helps develop rural areas and local economic life through cooperation between farmers, institutional kitchens and municipalities for example.
Lessons learned and repeatability
Many cities are looking for vehicle fuels and waste management systems that are environmental friendly and cost effective. This full-scale system for co-digestion of biological municipal waste and agricultural feedstock will demonstrate a new way to meet these needs. A new system in which the water addition in the biogas process is minimized will enable a cost effective production and distribution system.
This kind of technique should be interesting to replicate in other parts of Europe as well, especially in large agricultural districts.