Household waste is full of energy

By Jan Aagaard

Each time the citizens of Denmark’s capital Copenhagen put a bag of household waste into the collection container, it helps to ensure the supply of environmentally friendly energy to their homes. When the waste goes into the ovens at the city’s incineration plant, each bag generates three and a half hours of electricity and almost four hours of heating, to the benefit of the citizens and companies.

The energy from the waste is climatefriendly, since it is 80 percent CO 2 neutral on account of the waste consisting mainly of organic material such as food scraps. Furthermore, it helps reduce the need for energy from oil and coal. And 95 percent of the flue gases from incineration are cleansed before being released through the plant’s high chimney. Copenhagen’s household waste forms part of a circuit that has made Denmark one of the world’s leading countries in the waste management area. Although Danes produce a lot of waste, there has long been a tradition in the country to view waste as a valuable resource which as far as possible should be recycled or converted into energy.




In Denmark, only around 6 percent of waste is neither recycled nor incinerated, but specially treated or disposed of in a safe way. This is one of the lowest figures for waste disposal in the world.

Heating for 90,000 households Amagerforbrænding, an expert in converting waste into energy, is located just a few kilometres from the centre of Copenhagen, on the island of Amager. Each day the company receives waste from the households and businesses in the city corresponding to three swimming pools full of waste. This amounts to more than 400,000 tons of waste annually – or more than 10 percent of all waste that is incinerated in Denmark.

In addition, Copenhageners deliver 110,000 tons of waste annually to the recycling stations that Amagerforbrænding also operates. 75 percent of this wasteis industrially recycled to produce new products, while the rest, just like the household waste, is incinerated in the plant on Amager.

Each day 400 trucks deliver waste to Amagerforbrænding’s silo, where fully automatic cranes mix the waste then lift it into shafts feeding the plant’s four ovens. Here the waste is incinerated over two hours at a temperature of around 1,000°C.

The heat from the ovens is used to power two steam turbines that produce electricity for around 50,000 houses. When the steam has passed through the turbines, residual heat is recovered and used in the city's district heating network where it supplies heat for 90,000
households.

Incineration plant with a ski slope
While ovens and turbines convert waste into energy 24 hours a day all year round, an ambitious new project is taking shape in the offices of Amagerforbrænding, where plans are being made to extract even more green electricity and heat out of the waste, while keeping the environmental impact to a minimum.

To meet this objective, a new waste management centre will be built to replace the current incineration and energy plant
from 2016.

The new centre is visionary in both form and content. The world-renowned Danish architect firm BIG – Bjarke Ingels Group – won the international architect competition for the new centre with a project called Amager Bakke. In this unusual project, use is made of the centre’s height and size by shaping the roof of the enormous building as a ski slope, which the citizens of Copenhagen can enjoy.

The project thus fulfils Amagerforbrænding’s vision of gaining a distinctive architecture that accentuates the new plant’s environmental profile and forms part of the local community as an inviting recreational area. Amager Bakke also meets the vision to create an international ”beacon” in waste management and energy production.

More energy - less pollution
In principle the new plant will produce electricity and heat from waste in the same way as the current plant, but it will be equipped with a number of new and improved technologies. The plant will thus be able to supply 20 percent more energy per ton of waste than the existing one. With an annual CO 2 reduction of between 50,000 and 60,000 tons, the plant will also contribute to Copenhagen’s vision of becoming a CO 2 neutral capital by 2025.

The new plant will also have a high environmental profile in other areas. It will make less noise and produce less residual products, and the recycling of materials will also be increased. Air pollution will also be reduced since the plant will be able to remove up to 99 percent of the sulphur in the flue gases from the incineration of waste.

This article is from Focus Denmark Magazine, June 2011