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Low Carbon Power Generation
in Copenhagen
Part of our Low Carbon Copenhagen project ... project index >
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Biomass technologies
Biomass technologies — using plant materials and animal waste to generate energy and/or fuel — are a key part of Denmark's renewable energy portfolio. The Danes use wood, straw, refuse and human and animal wastes, and they produce heat, electricity and second-generation biofuel. In Copenhagen, there are two large installations and a pilot project.
The 1993 Danish Biomass Action Plan requires Danish power stations to use biomass for part of their fuel. Now almost all the woodchips, three quarters of the straw and half the wood pellets used in the country are burned for power and heat for district heating. In Copenhagen, heat and electricity are derived from wood and straw in new plants at Avedøre and at Amager (see right hand column). Also at Amager is a pilot plant making biofuel, solid fuel and recyclable by-products from unsorted household waste.
Biomass technologies
Biomass includes anything that contains carbon. Fossil fuels such as coal are technically biomass, though they are usually considered separately — the objective here is to use renewable sources.
There is much debate about the detrimental effects on world food prices and supply caused by using food crops to produce biofuels. Second generation biofuels, favoured in Denmark, use crop residue after the food element has been harvested, for example the straw from wheat once the ear has been taken, or cornstalks after the cobs have been removed. The yield is not much less than using the whole crop — 250 litres of ethanol from one tonne of wheat straw or 300 litres from one tonne of whole wheat.
While all types of biomass can be burned to generate energy, making biofuel requires enzymes. Waste is boiled in water inside pressurised containers. Enzymes are added at a lower temperature, and after a period of treatment the mixture is separated into solids and biofuel. The solid waste is separated into recyclable and combustible fractions, the latter becoming a new biomass source.
Denmark has set a target of 30% of total energy from renewable sources by 2025, which includes 10% renewable biofuels in the transport sector by 2020 (with a target of 5.75% for 2010). In 2008-09, the government provided 60m Kroner in subsidies for biodiesel trials in vehicle fleets and 200m Kroner for the development of a second-generation biofuel plant ..... next >
Top links
The official website of Denmark   www.denmark.dk
Use the search function to find articles on biomass and biofuels
Modern biomass utilisation : Energi E2   http://unfccc.int/eu_schultz.pdf
Presentation on renewable energy sources in Denmark (pdf)
Current status on biorefineries in Denmark : University of Copenhagen   www.biorefinery.nl/_4__Country_status_Denmark_IE42_150307.pdf
Details of energy from biomass in Denmark (pdf)
REnescience : More energy, less CO2 and more raw material   www.dongenergy.com/REnescience_fakta.pdf
Info on the pilot plant and diagrams of the biomass/biofuel energy cycle (pdf)
Production and use of bio pellets : Energie E2   www.northernwoodheat.net/ProductionandUseofBioPellets.pdf
Wood and straw pellet production at Køge, south west of Copenhagen (pdf)
DONG Energy A/S   www.dongenergy.com
Predominantly state-owned power generation company, operator of Avedøre Power Station
Vattenfall A/S   www.vattenfall.dk/10419amagervarketuk080121_7843254.pdf
Brochure on Amager Power Station (pdf)
YouTube   www.youtube.com/watch?v=KJgBQbLI5YQ
University of Minnesota video on the biofuel debate
YouTube   www.youtube.com/watch?v=OYAtSU2Xs-A
University of Minnesota expert talks about second generation biofuel research
YouTube   www.youtube.com/watch?v=sQAiH-FG9gE
Greenpeace video on Woking (UK) and their partner Energie E2, who talk about Avedøre
A tour around the world's first commercial-scale biomass plant, at Kalundborg, Denmark ...
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Avedøre 2 CHP plant
approved  September 1994
operational  mid 2002
power output  485 MW
district heating  570MW
wood pellets burned  300,000 tonnes/year
pellet source  the biopellet factory at Køge
straw consumed  150,000 tonnes/year
steam pressure  30,000kN per sq m
steam temperature  580 deg C
Sited next to the original coal-fired CHP (Combined Heat & Power) plant at Avedøre on the south side of Copenhagen, Avedøre 2 has multi-fuel capability. It can combine power from a biomass steam cycle, and a conventionally-fuelled ultra-supercritical steam cycle, with heat recovery steam generators. On installation, the ultra-supercritical steam turbine was the world's most efficient.
Components include wood and straw storage, boiler, ash separator and ash handling equipment. Flue gas filters restrict particle discharge into the atmosphere and bottom ash is recycled as fertiliser. It features the world's largest straw boiler, consuming 25 tonnes per hour.
The plant's operator, SK Power, has a reciprocal agreement with Vattenfall of Sweden for up to 200MW of power to be transferred between Avedøre 2 and the hydropower plant at Indalseiven, as demand requires.
Amager power station
A multi-fuel plant with three generating stations
Amager 1
re-commissioned for biomass  May 2010
re-configuration from coal cost  1.9 billion Kroner
woodchips burned  250,000 tonnes/year (or straw)
gross output  80MW power, 250MJ heat
steam pressure  18,500kN per sq m
steam temperature  562 deg C
Amager 2
commissioned  1972
straw consumed  250,000 tonnes/year
gross output  95MW power, 166MJ heat
steam pressure  9,000-11,000kN per sq m
steam temperature  480 deg C
Amager 3
commissioned  1989
fuel  currently burns coal
Amager power plant stands on the site of an ancient fortress that once protected Copenhagen. It supplies heat to the city's district heating system and electricity to the European power grid. The main fuel is biomass, with oil for starting the generating units. The three generating stations can supply heat to 115,000 households.
Combustion of biomass at of 1,500-1,800 degrees C produces super-heated steam that drives high-pressure turbines at 3,000 rpm for electricity. After passing through the turbines the steam loses some pressure and temperature, and is then used for district heating. Spent steam is condensed with cooling water from the sea and returned to the boilers.
The fly ash residues are recycled as additives for concrete manufacture. Flue gases are 'wet scrubbed' with water and limestone to remove the sulphur, producing gypsum that is used in plasterboard.
The reconfiguration of Amager 1 is part of an integrated plan to achieve a carbon neutral heating sector in Copenhagen by 2030. Other work includes a 4km tunnel, over 4m in diameter, between the plant and the city centre to carry steam to the heating network. CO2 emissions will be reduced by up to 630,000 tonnes per year.
The plant was built by Copenhagen Energy and was sold to Energi E2 in 2000. Vattenfall acquired it in 2006.
REnescience pilot plant
commissioned  December 2009
unsorted household waste treated  800kg per hour
project budget  7.3m Euros
REnescience stands for "renewables, science and renaissance of the energy system". Its pilot plant converts raw household waste into liquid biofuels with biogas, power, heat, fertilizer, metals and glass as by-products.
The continuous process (patent pending) involves treating waste with enzymes before passing it into pressurized gasifiers and separating the different fractions.
The REnescience project is located at Amagerforbrænding (waste-to-energy plant) and run jointly by DONG Energy and its subsidiary Inbicon.