Professional Engineering

For a technology feted as having such a bright future, carbon capture and storage (CCS) is taking a painfully long time to emerge from laboratory-scale demonstration through to commercialisation. It was more than four years ago that the previous government identified the process as a highly promising technique that could help the UK to slash its emissions and achieve its 2050 climate change goals. 

Subsequently, £1 billion was put aside to fund a project to demonstrate how the process would work in practice – capturing carbon dioxide from a fossil-fuel power station, transporting it by pipeline and storing it in an underground structure such as an oil and gas reservoir. 

A protracted competition saw a scheme at the Longannet power station in Scotland emerge as the eventual winner. But this project was scrapped at the end of last year after concerns about costs, mainly to do with the length of pipeline required from the Fife coast to the North Sea oil fields where the carbon was to be pumped. 

So we are now back to square one, with the Department of Energy and Climate Change prepared to say only that it will be launching an “accelerated” selection process “sometime soon”.

The procrastination is frustrating those who think that the UK, with its extensive expertise in the North Sea, is in a prime position to lead an industry that has enormous global potential. And there are fears that delays to the commercialisation of CCS could ultimately threaten the UK’s chance of meeting longer-term climate change commitments.

“The cancellation of Longannet was a real disappointment, and we have a history of several near misses on CCS projects in this country,” says Geoffrey Maitland, professor of energy engineering at Imperial College London, which has emerged as the central hub of CCS research. 

“Even though the funding of just one project was a minimalist approach – we would have been better backing several horses – Longannet at least had been through a detailed assessment process and had buy-in from a large number of partners from the industry.

“The decision to cancel it was almost inevitable in terms of short-term economic drivers – the recession has come at the worst time for things like this. The decision puts CCS off for quite a few years, and the longer we put it off, the more CO2 we will have to capture to keep levels down.”

Maitland says that the delays in getting a large-scale CCS demonstrator up and running are particularly frustrating because, he believes, the UK has the geological conditions and the engineering knowhow to take a lead with the technology. That could create many thousands of jobs. 

“There is the potential for the UK to get a large slice of the action,” he says. “Once CCS is proved commercially, there will be a domino effect, which means it will be retrofitted to existing power stations and installed on all newbuilds. There will be enormous business in building the capture technology and the pipeline structures, and the North Sea is a rich area in terms of storage capacity. Indeed, some small companies have already bought depleted oil and gas reservoirs and are waiting in readiness for this.”

While there are no large-scale demonstrations of CCS in the UK, that doesn’t mean that research isn’t ongoing into the techniques that underpin the process. Broadly speaking, there are three different capture technologies that can be fitted to fossil-fuel power stations: post-combustion, pre-combustion and oxyfuel (see box on page 36). Two of these – post-combustion and pre-combustion – can also be applied to industrial processes.

Capture accounts for two-thirds of the total cost of CCS, so much of the research and development effort is going into this area. The favoured technology at present is the use of amines as solvents to absorb large quantities of acidic CO2. The problem with this approach is that it’s extremely energy-intensive. Once the CO2 has been absorbed in the amine, a lot of energy is required to strip it out again. 

Separation of the CO2 from other flue gases has to be done at low pressure. That requires compression to take it to the supercritical state, which is the most suitable form for transportation and injection. This process also adds significantly to the cost.