Starting next year, stale bread, banana peels, coffee grounds and other food waste will be transformed into green fuel for Oslo's city buses. The Norwegian capital's new biogas plant will supply the fuel and also provide nutrient-rich biofertilizer for agriculture. The plant will be able to process 50,000 tons of food waste annually, converting it to environment-friendly fuel for 135 municipal buses as well as enough biofertilizer for roughly 100 medium-sized local farms.
Biogas is a carbon dioxide-neutral fuel produced from biomass such as food waste, sewage sludge and manure. Currently, 65 Oslo buses are powered by biogas produced from sludge from the city's sewage treatment plant. When the new biogas plant reaches its full capacity in 2013, the local bus company will have enough biogas for at least 200 buses.
Oslo's new biogas plant will produce the biogas using a method known as thermal hydrolysis, whereby raw materials such as waste or sewage sludge are boiled under high temperature and high pressure. The residue from the biogas production process may be used as liquid fertilizer with roughly the same nutrient content as compound fertilizer.
Biogas in buses means cleaner air and less noise for Oslo's 500,000 residents.