THW use carbon capture and storage to curb carbon dioxide emissions from fossil fuels

Carbon capture and storage (CCS, sometimes also referred to as ‘carbon capture and sequestration’) is the process of capturing the greenhouse gas CO₂ (carbon dioxide) and storing it, so it doesn’t enter the atmosphere.

Capturing

There are several methods of capturing carbon dioxide. This casefile refers to ‘post-combustion capture’ from a big CO₂-source like a coal burning power station, and does not, for example, refer to filtering carbon dioxide from the atmosphere. In post-combustion capture, the exhaust gases resulting from burning fossil fuels (called ‘flue gases’) are captured, and then treated chemically to remove the carbon dioxide. The chemical process is called ‘acid gas removal’ and is currently also used to remove the highly toxic hydrogen sulphide from flue gases.  

Storing

There are a lot of different ways to store carbon dioxide. One can use biological processes (for example by planting trees or using iron fertilization to encourage carbon dioxide-consuming phytoplankton growth in the oceans), chemical (for example by letting carbon dioxide react with magnesium- or calciumoxide to form magnesite or calcite) or physical processes by storing it in either gas form, liquid form, supercritical form (‘highly pressurized gas’) or in solid form. This casefile focusses mainly on one specific storage form, namely the physical process of injecting carbon dioxide in geological formations, for example in depleted oil and gas fields or in saline formations.

‘Clean coal’

CCS is often mentioned in combination with the term ‘clean coal’. Coal is the most used fossil fuel to generate electricity (around 42% of electricity is generated by coal, responsible for 28% of global carbon dioxide-output, see: Power generation from coal, 2010). The ‘clean coal’-movement aims to make this process ‘cleaner’ by applying several techniques, one of which is CCS.