Carbon Capture

ARC is working towards making Amager Bakke CO2-neutral. With a large scale plant for carbon capture, Amager Bakke will be capable of capturing up to 500,000 tonnes of CO2 annually. This will be an important contribution to the Danish climate goals as well as Copenhagen’s goals of reaching CO2-neutrality.

How carbon capture works

CO2 is captured by a chemical process in which the CO2 molecules are washed out of flue gas and captured in a liquid.

1. Your waste becomes electricity, district heating… and CO2

ARC receives combustible waste every day from homes and companies at Amager Bakke. ARC utilises the energy in the waste for electricity and district heating.

Like all other combustion processes, waste energy also emits CO2. But unlike air exhaled from our lungs, it’s easier to capture. Amager Bakke is perfect for capturing CO2, because the plant is in operation 24/7/365. That provides a large, stable supply of CO2 which is necessary for efficient carbon capture.

2. Absorber

When the flue gas from the waste incineration has been purified, it’s approximately 40 degrees, and consists almost entirely of CO2 and water vapour. The purified flue gas starts by passing through an absorber. – As the name suggests, this is where the CO2 is absorbed from the flue gas.

The absorber is shaped like a tower, with smoke fed in from the bottom so that it rises upwards, while being flushed from above with an alkaline amine liquid. CO2 is bound by and into the amine liquid. Only the water vapour and a the left over amount of CO2 is exiting the chimney at the plant. The CO2 containing amine liquid continues on to the desorber.

3. Desorber

From the absorber, the CO2 containing amine liquid continues on to the desorber, which is the most energy-intensive part of the process. In the desorber, the liquid is heated up to approximately 105 degrees. This releases the CO2 from the amine liquid. – It’s a bit like fizzy drinks going flat when they get warm. The CO2 can then be collected and transported for storage or utilization.

Once the amine liquid has released the CO2 into the desorber, the liquid can easily be used again. Once cooled, it’s led back to the absorber, where it captures CO2 again. And again. And again.

Due to the high energy consumption, it can be difficult to make carbon capture climate-friendly. But Denmark has the big advantage of our widespread district heating network where excess heat can be reused. This also applies to carbon capture at Amager Bakke: We have a goal of harvesting the surplus heat and utilize it in the district heating network when capturing CO2 at a large scale in the future. This will enable net-zero energy consumption.

4. CO2 storage and Power-to-X

The CO2 collected from the desorber is pressurised and stored in tanks, just like the CO2 cartridges used for homemade soda: when CO2 is mixed with water, it turns into carbonated water.

The captured CO2 can either be stored below ground, or eventually converted into green fuels
(Power-to-X). According to GEUS, the Danish underground is particularly suitable for storing CO2, and it will be possible to store 500-1000 years of total Danish emissions at the current level.

5. CO2 negative = Climate positive

In CO2 accounting, a distinction is made between CO2 from fossil sources, such as plastic, petrol and gas, and CO2 from biogenic sources such as wood, straw and potato peelings. Even though CO2 is CO2, a distinction is made between what is already in rotation between plants and the air (biogenic), and all the extra CO2 we add to the atmosphere by digging or pumping it up from underground. Something is only considered CO2-neutral if it only emits CO2 from biogenic sources, e.g. if energy comes from burning straw or wood pellets.

A lot of the residual waste at Amager Bakke comes from biogenic sources. But there is still fossil residual waste ending up at Amager Bakke (and any other waste-to-energy plant). If all of the CO2 (from biogenic and fossil sources) in one waste-to-energy plant could be captured, the plant would become CO2-negative – It’s not just the extra CO2 that’s removed, but also the CO2 that was already in circulation. Biogenic CO2 is thus removed from the atmosphere instead of being recycled.

Because carbon capture can lower the total amount of CO2 in the atmosphere, the technology is considered one of the tools that can help effectively limit global warming in the short term.

FAQ about carbon capture

Visit ARC

Enjoy a tour of the plant and a presentation of ARC’s business areas, including how we handle everything to do with waste.

Visits are intended for companies, associations, organisations and other guests interested in waste management.

World-class waste energy plant

Amager Bakke (CopenHill) is among the best in the world in terms of environmentally friendly energy and innovative architecture. It offers the unique experience of green recreational areas, skiing, climbing and a waste energy plant. Amager Bakke boasts highly efficient energy production and supplies electricity and district heating to the citizens of Copenhagen. Amager Bakke is also working on carbon capture aiming at capturing up to 500,000 tonnes of CO2 annually.