Carbon Capture and Storage – A Roadmap for Scotland
Pre-combustion capture - removal of CO2, prior to combustion, to produce hydrogen
Oxy-fuel combustion capture - burning fossil fuels in pure oxygen as opposed to air resulting in an exhaust gas of mainly CO2 and water vapour
CO2 capture is likely to be most economic at large point sources of CO2 such as power stations and large industrial plants. In most cases these will not be close to a suitable underground geological store and therefore the CO2 will have to be transported.
Transport is currently the least complicated element in the CO2 capture and storage chain as the technology is already in existence and costs can be realistically estimated.
The main complication with CO2 transport is that CO2 behaves differently under varying pressures and temperatures and therefore transport of CO2 must be carefully controlled to prevent solidification and blockages occurring.
There are currently two methods used to transport large volumes of CO2 by industry:
CO2 storage is the process of taking captured CO2 and then placing in a store where it will not be in contact with the atmosphere for thousands of years. Storage of the CO2 underground in deeply buried porous rocks beneath a layer of impermeable rock (cap rock), which acts as a seal to prevent the CO2 from leaking out, is the most obvious option at present.
There are three main types of proposed underground storage sites:
Depleted Oil and Gas Reservoirs
Deep Saline Aquifers
Deep Unminable Coal Seams
You can read more about CCS at The Scottish Centre for Carbon Storage