Capture & separation of CO2

A number of means exist to capture carbon dioxide from gas streams, but they have not yet been optimised for the scale required in coal-burning power plants.

The focus in the past has often been on obtaining pure CO2 for industrial purposes rather than reducing CO2 levels in power plant emissions.

Where there is carbon dioxide mixed with methane from natural gas wells, its separation is well proven.

Several processes are used, including hot potassium carbonate which is energy-intensive and requires a large plant, a monoethanolamine process which yields high-purity carbon dioxide, amine scrubbing, and membrane processes.

Development of CCS for coal combustion has lost momentum in the last few years, partly due to uncertainty regarding carbon emission prices.

The Global CCS Institute established in 2009 and based in Australia aims “to accelerate the development, demonstration and deployment of carbon capture and storage (CCS), a vital technology to tackle climate change and provide energy security.”

In mid-2010 the IEA published a report saying that CCS was challenging, and quoting $26 billion committed in the previous two years to CCS projects.

In mid-2016 the Global CCS Institute said that there were 15 large-scale CCS projects in operation, with a further seven under construction.

The total CO2 capture capacity of these 22 projects is around 40 Mt/yr.

There are another six large-scale CCS projects at the most advanced ('define') stage of development planning, with a total CO2 capture capacity of around 6 Mt/yr.

A further 12 large-scale CCS projects are in earlier stages ('identify' and 'evaluate') of development planning and have a total CO2 capture capacity of around 25 Mt/yr.