special feature
What difference?
This feature was funded by
Ramboll UK
Did you know that
one person produces  500kg waste/year
one tonne of waste yields  2MW heat energy
and yields  2-3MW electricity
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Low Carbon Power Generation
in Copenhagen
Part of our Low Carbon Copenhagen project ... project index >
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Waste-to-energy in Copenhagen
Denmark has long relied on waste-to-energy processes for dealing with municipal waste. Its first plant was commissioned in 1903, and from the start this method of waste disposal was linked to supplying heat for district heating systems and energy for power generation. Copenhagen processes 25-40% of its waste this way, three quarters of it household refuse, producing some 720,000MW of heat and 210,000MW of power.
Incineration is the most commonly used waste-to-energy process used in Denmark. Steam, heat or power are produced in any combination, and plants can be up to 98% efficient. However, there are other technologies that produce gas, liquid and solid combustible fuels. Other thermal technologies include gasification, depolymerisation and pyrolysis. Non-thermal technologies include anaerobic digestion, fermentation and mechanical-biological treatment.
There are three waste-to-energy facilities in central Copenhagen — Vestforbrænding to the west and Amagerforbrænding to the east which burn refuse, and the (much smaller) treatment works at Rensningsanlæg Lynetten, burning sewage sludge. All are combined heat and power (CHP) plants, supplying energy for district heating and electricity. Also supplying the Copenhagen networks are the multi-waste incineration plant at Nordforbrænding in Hørsholm, north of the capital, and the KARA plant at Roskilde further west.
The process
The following diagram illustrates incineration with wet flue gas treatment —
see it larger and read its key. Diagram courtesy Rambøll.
Waste-to-energy diagram courtesy Ramboll
In Copenhagen's CHP plants, municipal waste is delivered by road and tipped into huge concrete bunkers. It's mixed and extracted by crane grabs and fed into shafts leading to the furnaces. Here the waste sits on moving grates that take it through the flames. Hot exhaust gases leave the furnaces and heat water in a series of heat exchangers. The hot water, or steam, can be used directly for district heating, or the steam used to drive turbines to produce electricity.
The incineration of waste results in ash or slag at the bottom of the combustion chamber, and fine particles (fly ash) in the exhaust gases. These gases often contain hazardous substances and must be treated, or 'scrubbed', as well as filtered before discharge through the chimney stack. The bottom ash can be cleaned and recycled as a concrete additive — bottom ash residues amount to about 200kg per tonne of waste. Fly ash may need disposal as hazardous waste in accordance with environmental standards.
Why it works in Copenhagen
Denmark's waste-to-energy plants represent a different approach to waste disposal than that found outside Scandanavia on a large scale. In 2008, Copenhagen, helped by legislation, sent only 2.2% of its 904,216 tonnes of waste to landfill — 20 times less than in 1988. The Danish average is 6-10%. Copenhagen is aiming for a figure of zero, as outlined in its Waste Management Plan 2012 (adopted 27th November 2008). A further 25-40% goes to waste-to-energy plants and the rest is recycled.
Among the factors that have made waste recovery for heat and power effective in Denmark is the consistent way that the combination of waste incineration and district heating have been promoted over a long period. Both political will and taxes and subsidies have been aimed at their joint development. Denmark's climate makes heating essential for most of the year, and landfill sites had already started to fill up by the early 20th century.
Incineration continues to cause controversy outside Scandanavia, though it is used widely in Japan and Taiwan. The by-products and residues can be hazardous. The Danes count the benefits as including the reduction of waste volumes, the production of energy, the conservation of fossil fuel resources and the diminution of CO2 emissions. Others have argued against the process on account of the cost of meeting air pollution standards and reaching the high technical standards needed for efficiency. To make the energy recovery aspect work, a reasonably sized district heating scheme is required.
However, the Danes are committed. It is now illegal in Denmark to send waste that could be incinerated to landfill instead. Copenhagen's Waste Management Plan 2012 states that, "In the City of Copenhagen we wish to reduce impacts on the environment, including climate, through sustainable management of waste. Also, we wish to ensure that citizens of the city are satisfied with waste management services." ..... next >
Top links
Waste Management Plan 2012 (Affaldsplan 2012)   www.kk.dk
In Danish, but there's a shorter verson in English that you can download (pdf)
Sustainable Cities   http://sustainablecities.dk
Case study : Copenhagen: Waste-to-energy Plants
Vestforbrænding   www.vestfor.com
Operates Denmark’s largest waste incineration plant
Amagerforbrænding   www.amfor.dk
Operates a CHP plant in Copenhagen
DONG Energy A/S   www.dongenergy.com
Predominantly state-owned power generation company, operator of Avedøre Power Station
EnergyMap   www.energymap.dk
Danish internet portal for energy- and climate-related solutions
ZMags   http://viewer.zmags.com/showmag.php?mid=wssgg
100 Years of Waste Incineration in Denmark : Rambøll publication
ZMags   http://viewer.zmags.com/showmag.php?mid=wsshq
Waste-to-energy : Rambøll brochure
YouTube   www.youtube.com/watch?v=iioOVevReOs
An overview of waste-to-energy by FreeEnergyNews.com
See what it's like inside the Amagarforbrænding plant ...
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images  courtesy Rambøll
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"The less waste the better
— it's as simple as that."
Copenhagen Waste Solution, City of Copenhagen, 2008
location  Glostrup
waste received  1,500 - 1,600 tonnes/day
waste breakdown  50% domestic
waste incinerated (2008)  563,000 tonnes
bottom ash produced (2008)  100,000 tonnes
flue gas waste produced (2008)  300,000 tonnes
households supplied with heat and power  155,000
district heating energy  1,390GW
electricity  245GW
Vestforbrænding is the largest waste-to-energy plant in Scandinavia. 80% of the energy it generates goes to district heating and 20% to electricity generation.
Its waste bunker is 100m x 20m x 10m deep. Waste is grabbed in 5 tonne handfuls by three cranes feeding four hoppers, one per furnace. The first two furnaces (1970) each burn 12 tonnes/hour, Plant 5 (1999) incinerates 26 tonnes/hour and Plant 6 (2005) 35 tonnes/hour. Waste is ignited in air on moving grates. Bottom ash is reprocessed, about 95% is recycled to the construction industry. Hot gas from the furnaces heats water into high-pressure steam.
Ammonia is injected into the combustion chamber to reduce emissions of nitrous gases through the flues. Activated carbon filters trap fly ash and remove dioxins and other harmful substances. A wet (water) scrubbing system washes flue gases to remove hydrochloric acid, heavy metals and sulphur dioxide. This turns the sulphur into gypsum, which is sent to landfill. Other solid flue residues are shipped to Norway for disposal. Effluent is neutralised with lime before being sent to a wastewater treatment plant.
The plant continually monitors flue gas flow and temperature at different locations in the furnaces, as well as oxygen rate, water rate, nitrous oxide levels, dust, sulphur dioxide levels and total organic carbons.
A flue gas condensation project was implemented in one of the CHP units and with the heat capacity from the turbine, the total efficiency reached 100% at an average of 120MW of heat.
source  www.vestfor.com
location  Amager, Copenhagen
waste received  400 truckloads/day
waste breakdown  50% domestic
waste incinerated (2008)  435,900 tonnes
households supplied with heat and power  140,000
Amagerforbrænding is a partnership company owned by five Copenhagen municipalities — Dragør, Frederiksberg, Hvidovre, København and Tårnby. It takes waste from all five, representing 10% of the municpal waste in Denmark. It has provided energy for district heating since 1970 and for electricity generation since 1990. A year later it began operating recycling stations.
The heat of combustion turns water into high-pressure steam, 20% of which is used for electricity generation. The rest is used in the district heating system.
Flue gas passes through several cleansing cycles. Fly ash residue is exported to Norway for disposal. Metal is reclaimed from the bottom ash and the remainder is re-used in the construction industry.
Visitors can take a guided tour of the plant, the oldest of its kind in Denmark.
source  www.amfor.dk