Greenhouse gas emissions from fossil-fuelled power plants and large industrial point sources such as cement plants or steel works contribute significantly to climate change. In order to limit global warming to 2°C above pre-industrial levels – a threshold that in the opinion of climate scientists would reduce the risks and impact of climate change – these emissions have to be drastically reduced as soon as possible.
This is where a suite of technologies known as carbon capture and storage (CCS) may be of crucial importance. The idea of CCS is simple: capture the greenhouse gas carbon dioxide (CO2) where it is produced, for example at coal-fired power plants, before it reaches the atmosphere. Then transport the captured CO2 to storage sites where it can be safely held for long periods of time without being released into the atmosphere.
However, CCS comes with challenges: the capture process has to be as cost effective and energy efficient as possible, transportation must be safe and fit for purpose, and storage sites have to be secure and, if possible, located close to the CO2 source.
In the last few years, more and more large-scale capture facilities have become operational – for example, at the coal-fired Boundary Dam power station in Saskatchewan in Canada, where one million tonnes of CO2 are captured each year – and more are planned or are under construction.
Transportation of CO2 via pipelines has been proven to be secure as pipelines for CO2 transportation have been around for decades, with the US having a pipeline network of more than 2000km alone. This shows that technological and engineering obstacles associated with capture and transport of CO2 can be overcome and that widespread rollout of capture facilities is possible in the near future.
Scientists have proposed several ways to store the captured CO2, including storing it at the bottom of oceans, in volcanic rocks, in abandoned mine shafts and in porous sedimentary rocks located deep underground. The latter method is favourable for many researchers, as sedimentary rocks are widespread all over the world and they are well understood – mainly because they host most of the known oil and gas fields worldwide.