All waste becomes raw material either in the production of new products such as new plastic products, bio methane, bio fertilizer or as heat and electrical power (see figure 1).
Food waste, garden waste and sewage become biogas, soil-products and bio-fertilisers. Food waste and wastewater contain useful nutrients for agricultural production, and the recycling is important for non-renewable resources such as phosphorus.
A biogas plant processes food waste from households and industrial companies into green fuel .The plant is designed to minimize transport and emissions to air. Climate neutral biogas is also produced from sewage sludge and upgraded for use as transport fuel at another facility. Together the two plants produced 3 million Nm3 biogas in 2015. All the waste trucks and 150 of the 1204 buses in Oslo (2015) are fuelled by biogas. Biogas city buses reduce fossil CO2 emissions as well as noise and air pollution.
After recycling, all residual waste is used as an energy source. Oslo’s two waste-to-energy incineration plants annually generate around 940 GWh of district heating energy and 160 GWh of electricity. The energy recovery rate of the incineration plant is 99 % for household waste. The district heating system is serving more than 160,000 citizens or 20 % of all heating demand in Oslo.
As a world-first, carbon capture and storage from non-recyclable waste is piloted at the city-owned Klemetsrud Plant. Carbon capture and storage of these emissions will help cut 12 % of Oslo’s CO2-emissions.