Industrial emissions...
but without the CO2

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Castor
There is a general consensus the world over that carbon dioxide (CO2) emissions must be cut if we are to slow down climate change. The best way in which to do this is still under discussion by politicians and scientists alike, but one technical and immediate option that is increasing its profile is ‘carbon capture and storage’.

The raised profile of this potential solution is due in part to the outstanding results of the CASTOR project, which include the world’s largest carbon capture pilot facility. Among the achievements of this first-of-a-kind plant, located in Denmark, was a demonstration of the possibility of capturing 90 % of the CO2 that would normally be released into the atmosphere from a coal-fired plant.

Generally, the amount of CO2 taken out of the atmosphere by plants and other natural carbon sinks such as oceans is roughly equivalent to the amount put into the atmosphere by respiration and decay. But this delicate balance is upset when additional CO2 makes its way into the atmosphere due to human activities such as emissions. One of the conclusions of the European Research Project for Ice Coring in Antarctica (EPICA) was that the global atmospheric concentration of CO2 has increased by 30 % since the industrial revolution.

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Making fossil fuels clean

While much of the attention has been focused on using alternatives to fossil fuels, carbon capture and storage involves trapping CO2 as it is emitted and preventing it from entering the atmosphere. But it is not as simple as channelling the flue gas into a container and closing the lid. As it is not feasible to compress all of the gases, which may include oxygen, water vapour or nitrogen, the various components of the flue gas must be separated.

There are a number of industrial capture processes on the market already. Each has been developed for an individual field of application, adapted according to the nature of the flue gas composition, temperature and pressure. CASTOR uses post-combustion capture.

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New records for carbon capture

For post-combustion capture, absorption technology is a leading option. However, integrating it into an existing power station will decrease the efficiency of generation by 15 % to 20 % and increase the costs of producing power by up to 50 %. The CASTOR project, bringing together 30 partners from 10 EU Member States plus Norway, set about removing these deterrents to make post-combustion capture more appealing. The aim was to cut post-combustion capture costs from EUR 50 or EUR 60 per tonne of CO2 to EUR 20 or EUR 30 without harming efficiency. In terms of volume, the ambition was to developtechnologies that enable the capture and storage of 10 % of all CO2 emissions, which corresponds to around 30 % of the CO2 emitted by Europe’s power and industrial plants.

The project succeeded in this. The pilot demonstration set up at a coalfired power plant in Denmark as part of CASTOR was the first of its kind and remains the largest in the world. So successful was the facility that successive projects have reproduced parts of it when conducting separate studies on CO2 capture. A glance at the pilot’s results explains why: the team was able to demonstrate that a CO2 recovery rate of 90 % was feasible. The demonstrator is able to capture an impressive one ztonne of CO2 every hour for an estimated cost of Eur 35 per tonne of CO2.

Not all of the issues surrounding carbon capture have been solved. But the unique CASTOR facility means that current and future ideas can be taken from laboratory scale to pilot scale either by current CASTOR partners or other researchers. CASTOR’s system relies on the amine washing process. This involves dissolving the CO2 in a solvent and then recovering the liquid solvent with the CO2 and other flue gases locked into it. The CO2 is then extracted by heating.

These results should not be underestimated. ‘When we launched the idea, CO2 capture was a kind of dream rather than real technology that could be implemented,’ says project coordinator Pierre Le Thiez. ‘CO2 capture was a concept. Now the technology is very much a reality, not just in Europe but worldwide.’

Once the CO2 has been captured, it must of course be stored. Here the project team was looking for advances in terms of capacity, security and environmental acceptability. The results of geological modelbuilding, reservoir simulation model-building, seismic simulation model-building and experiments on samples all provide clues as to the optimum storage facility for the future. The team also increased understanding of how to prevent CO2 leaking through wells, rock and faults. The challenge now is to demonstrate this to the general public and gain acceptance of storage technology. Perceptions of CO2 as a dangerous gas mean that resistance is currently quite deep seated.

The huge leaps in knowledge and technology made possible through CASTOR were no doubt in part due to the involvement of so many different stakeholders. The project brings together representatives from the oil and gas industries, power companies (CO2 emitters), technology equipment suppliers and European research centres and universities.

Good for business as well as the environment

Each of these sectors is set to benefit if carbon capture and storage takes off. While industry is under pressure from local regulations and environmental groups to cut CO2 emissions, it has added pressure from EU targets and international commitments. Under the EU Emissions Trading Scheme, strict limits have been set on CO2 emissions from iron and steel plants and the glass, cement and brick sectors. As of 2008, plants must pay a fine of EUR 100 per excess tonne of CO2 emitted. Cutting emissions will therefore boost competitiveness by lowering costs.

More research is needed before carbon capture and storage canbecome a permanent part of Europe’s energy portfolio. But as governments and industry race to meet EU and international emissions commitments, the results of CASTOR suggest that the concept is a real contender at the starting line.