September 24, 2021

I, Science

The science magazine of Imperial College

Longannet Power Station

For many years the idea of carbon capture and storage has been floating around as a solution to global warming. But is it viable?

With the government’s publication of a roadmap for carbon capture and storage (CCS) earlier this month, and the inclusion of CCS in the Committee on Climate Change’s recent plan for reducing carbon emissions, this approach is obviously being heavily relied on. However, CCS has not had an easy time in previous attempts, with plans at Kingsnorth triggering prolonged protests at the power station (until they withdrew plans in 2010) and the proposed scheme at Longannet unable to go ahead as the £1bn government subsidy proved not large enough to attract investment. This seems a good time to review what CCS is. Does it work? And what are the issues?

CCS is the process by which carbon is removed from the atmosphere, power stations, or fuel before burning and then pumped underground. The idea is that we can keep burning fossil fuels whilst not experiencing any further global warming – more colloquially known as having your cake and eating it too. The process has been regularly advertised with artistic interpretations of futuristic artificial trees that are intended to draw CO2 from the atmosphere; however, this is a pipedream and current proposals only look at removing CO2 at the power plant or during other CO2 intensive industrial processes like cement manufacture. The removal, or capture, of CO2 is actually quite successful, whether performed before burning coal by turning it into hydrogen for burning and CO2 for storing, or afterwards by using chemical solvents to remove it from the flue gas that is produced. The latter is applicable to natural gas as well as coal and has the advantage of being able to be fitted to current power stations.

All these methods produce an efficiency of CO2 capture of more than 80%. However, it is the storage where issues arise. The plan is to pump the CO2 into the reservoirs where the oil and gas originally came from (sometimes it could even be used to help get more oil and gas out) or to put it into brine aquifers. The UK has ample supply of storage in the North Sea, but in the US there have been wide-ranging estimates of the volume of usable storage, which means it might either work for only two full-functioning years or forever. This inability to know if it is a viable mechanism is worrying. And this is where the main criticism lies, voiced both by the UK Energy Research Centre and parliament’s office for science and technology.

The fact that there has never been a commercial scale CCS scheme means that we are not able to say whether it will definitely work or how much it will cost – and as the Longannet project found, it may cost a lot more than first thought. The use of CCS in our government’s long-term plans is worrying, as by keeping this golden solution that we are promised will be developed it allows us to keep on with fossil-fuel burning as we believe it will all be fine when CCS is finally developed. The fact that the solution may never appear, or could be incredibly expensive when finally developed, seems to be left out of the government’s statements and plans for the future.

Image: flickr | _gee_