In the town of Rapperswil-Jona, you are not likely to find standard-issue black refuse sacks. Here they come monogrammed and in a range of colours depending on their size: orange for 17 litres, green for 60 litres and red for 100 litres. But have you ever given any though to what happens to your rubbish once it is picked up by the refuse collectors?

The Swiss lead the world when it comes to recycling, whether glass, aluminium, PET bottles, paper, vegetable and garden waste, or electrical and electronic goods. All other waste is put into refuse sacks, some which are more colourful than others. These are then incinerated at a local waste incineration plant, generating electricity as well as energy for district heating systems.

What is thermal recovery?

In Switzerland, the municipalities are responsible for the collection of residual waste and its transfer to the nearest waste incineration plant. In the canton of Vaud, this is the Tridel plant in Lausanne. Ever year, it takes delivery of 160,000 tonnes of waste, which arrive there by train. The Tridel incinerators usually work 24 hours a day.

What happens to the rubbish once it reaches Tridel? First, the bulk waste is crushed before being mixed with the rest of the rubbish. A huge crane feeds the waste into the incinerators’ two hoppers. High temperatures are needed to break down most of the waste, without the need for extra fuel. The fires are stoked by a supply of forced air under the combustion grate, causing temperatures in the combustion chambers to rise to 1,000 degrees Celsius. The boiler is fitted with 42 kilometres of water-filled pipes. This hot water is converted into steam, which then passes through a turbine and generator to produce electricity. The steam also feeds the Greater Lausanne districting heating network, supplying 18,000 people, which is equivalent to a town the size of Nyon or Vevey, with heat and light.

As the steam is extracted, the temperature of the flue gases falls to below 200 degrees Celsius as they exit the boiler. These gases then undergo a three-stage purification process, whereby electrostatic filters, a wash tower and catalyser remove any dust particles, heavy metals, oxides and dioxins before sending the neutralised air back into the atmosphere.

Meeting low-emission targets

There is a waste incinerator plant in every region of Switzerland. Many were upgraded in recent years in order to comply with the stringent emission levels set out in the Federal Ordinance on Air Pollution Control. A new integrated power plant is currently being built in Bern. In addition to a wood combustion plant, Forsthaus will also feature a gas-fired combined cycle plant, enabling it to convert rubbish, wood and natural gas into electricity, steam as well as energy to power district heating networks. The arrival of the new power plant will help the city of Bern when nuclear power is finally phased out.