CCS: Time for action
It is widely believed carbon capture and storage (CCS) will play a major role around the world in the bid to meet our future electricity demands at the same time as reducing emissions of carbon dioxide. The basic technology for CCS has been around for decades but in recent years researchers like Professor Stefano Brandani have been investigating new techniques and new types of materials which promise to make CCS not only much more efficient but also more economic...…
Article by Peter Barr
Even though the media and some politicians may give the impression that carbon capture and storage (CCS) will enable us to “have our cake and eat it,” building lots of coal-fired power stations which would actually reduce our carbon footprint, there are no easy solutions to the energy problem. CCS has the potential to reduce emissions of carbon dioxide by 90 per cent, while still taking full advantage of our vast reserves of fossil fuels, but the testing of CCS systems in real-world conditions is only beginning – and it may be another five years before the first commercial-scale CCS system is running.
The benefits of CCS are obvious but there is also a downside – even though they will clean up emissions, without proper integration CCS systems may well account for up to 40 per cent of the total energy output of a typical coal-fired power station. Researchers may be able to reduce this to 30 per cent in the very near future, but more effort is needed to achieve further improvements. There is also no escape from the fact that CCS will take some time to implement and will be very expensive, but the cost of doing nothing would be catastrophic, says Professor Stefano Brandani of the Institute for Materials and Processes in the School of Engineering at the University of Edinburgh.
The UK Climate Change Act aims to cut our emissions by 80 per cent by the year 2050, but even if we meet our targets, other countries may ignore the problem and “tip the ecological balance,” so it's vital to do something now, says Brandani. Most scientists agree we need a mix of solutions – including renewables, fossil fuels and nuclear – to meet demand for electricity. Even in Scotland, where renewables offer tremendous potential, no single solution would meet all our energy needs, but we will need to use at least two of the three major options – or we will find it very hard to reach our targets.
Fossil fuels will also play a major role in meeting future energy needs, whether we like it or not. According to the International Energy Agency (IEA), fossil fuels will still account for 80 per cent of the world’s primary energy mix in 2030 and coal will continue to generate half of our power. And that is why Brandani is determined to make CCS more efficient and cheaper.
Every new power plant being constructed in Europe is CCS-ready and most of the others can easily be retrofitted, but the first generation of CCS systems is still at the prototype stage. In Scotland, for example, ScottishPower last year launched a test project to capture carbon dioxide emissions from the Longannet power station in Fife – the first time that this has been done at a working coal-fired power plant in the UK. The prototype, developed by Aker Clean Carbon, is a small-scale demonstration of what is to come, testing the efficiency of different solvents but Brandani says that this is an important first step towards a commercial-scale CCS project and agrees with ScottishPower that CCS offers the potential to create a whole new industry on the same scale as North Sea oil, creating thousands of jobs.
The different options for CCS systems all have their merits, says Brandani, and all will cost roughly the same. Amine-based solutions (using chemical solvents) have been used to separate carbon dioxide in industrial plants since the 1920s and new plants continue to move the technology forward. For example, Mitsubishi has a pilot plant in Malaysia which captures emissions at a rate of 200 tonnes per day, but this is still very small compared to the total emissions from a typical 1GW (i.e. 1,000MW) coal-fired power station – about 750 tonnes per hour or almost 100 times more.
“We are confident that these solutions work but we need to improve them,” says Brandani. “We will need a significant research effort to optimise first-generation amine-based systems, and also get them working on a much larger scale. In parallel, we must develop second- and third-generation solutions to address the limitations of the first generation.”
According to Brandani, one of the best ways to improve the efficiency of post-combustion solutions is to develop new types of adsorbents, screening novel microporous materials to identify the best candidates. Ultimately, Brandani hopes these new high-tech “sponges” will be able to reduce the energy diverted to CCS by about 50 per cent. “We are working on novel adsorbents and processes, to develop the underpinning science for these technologies, and all of this takes time and money. We can only test so many new materials a day, but regardless of cost, we must do it.”
Brandani is currently engaged in a wide range of research projects, based in his laboratory in the University of Edinburgh. For example, his group has developed a semi-automated measuring device and a set of numerical tools to analyse the properties of various nanoporous materials, and a novel type of apparatus that will be used to “characterise the performance of adsorption columns with several grams of solid material.” This new device will have “direct applications to the characterisation of process parameters used for gas separations,” and the main aim is to develop a proof-of-concept unit that will extend the capabilities of the group's laboratory.
Another of Brandani's long-term projects is research for the US Department of Energy, in partnership with UOP, a Honeywell company, to investigate and synthesise novel nanoporous materials for post-combustion carbon capture. Now in its third year, the project involves rapid screening of novel metal-organic adsorbents for carbon capture, using a new type of “zero length column apparatus” (a chromatographic technique that can provide both the equilibrium and kinetic properties of adsorbents) developed by Brandani which allows researchers to test the effects of simulated flue gas on a very small scale in the lab. This new device contains a tiny amount (less than 15mg) of the material used to “filter” the gas passing through it, extracting the carbon dioxide, and a mass spectrometer to study the influence of water and other impurities. The University of Edinburgh is the only non-US research partner involved in the project.
The new technique developed by Brandani makes it possible to screen more materials and more variants than ever before. All the candidate materials are compared and ranked according to different criteria such as how much of the gas they adsorb, how quickly they do it and how often the material will need to be replaced. How will they cope in dynamic conditions? How will they interact with water and other impurities like sulphur dioxide? How much will they cost?
Brandani's work focuses on so-called “second-generation solutions.” But he strongly believes that even though researchers may soon be able to double the efficiency of CCS, we still need to implement first-generation solutions as soon as we can. “Twenty to 30 years from now, demands may get more stringent and we may need to capture 95 per cent of all emissions, compared to our targets today. But the key thing is to start doing it now, starting with power stations, then quickly moving on to other sources such as industrial plants.”
This urgency is not just because we have no time to lose but because we need to see different systems in action. “We need to find out which technology will work best under dynamic conditions,” says Brandani. The UK demonstration projects in the pipeline are for capturing carbon dioxide at a scale of up to 400 megawatts of electrical output. This is enough for the purpose of testing the full carbon capture and storage chain, he says, and it can be easily scaled up in future.
There is a more favourable environment for CCS today than 12 years ago in the wake of the Kyoto Protocol, when Brandani's work was starting to get off the ground, but he strongly believes that we must start implementing CCS solutions now, not just in power stations but wherever greenhouse gasses are emitted, including industrial plants. Working as part of a team based in the University of Edinburgh, Brandani also sees great potential in Scotland for CCS, but says that if we want to be a leader, we have to start investing right away – with demonstration projects like Longannet key to success – so we can learn from our experience and create the collaborative framework required to develop the next generation of CCS systems.