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'The Ugly Truth'

by Tracey Brown, director of Sense About Science

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Capturing carbon: sensible solution or dangerous detour?


The UK is committed to reducing greenhouse gas emissions by at least 80% by 2050. Achieving this target will undoubtedly require a decreased reliance on the burning of fossil fuels. However, another question has been garnering more and more interest: is it possible to make coal and gas cleaner?

Carbon capture and storage (CCS) technology extracts the waste carbon dioxide from power plants before storing it deep below the earth’s surface. Supporters claim that CCS can capture 90% of the CO2 produced from burning coal and gas, while the IPCC has highlighted the considerable potential of CCS for mitigating greenhouse gas levels over the coming century.

But CCS certainly isn’t the finished article. Only a handful of CCS systems of commercial scale are currently in operation globally, and numerous projects have been scrapped in the last few years. Opponents argue that CCS is too costly, encourages fossil fuel burning, and diverts money away from other avenues of carbon mitigation. Some have also raised concerns over the reliability of the carbon stores: what happens if they leak?

On Tuesday 22nd October 2015, our expert panel (Dr Niall MacDowell, Dr Clair Gough, Professor Colin Snape, and Mrs Michelle Bentham) answered your questions.

If you have a question on an energy related issue then get in contact with our energy panel via Twitter, @senseaboutsci using #energypanel, or email us at [email protected].

Image by Vattenfall (CC BY-NC-ND 2.0)


24. "Will the UK be using CCS anytime soon?" (Paul Hutchinson) 

Dr Clair Gough (CG): "There are two projects on the table in the UK: the White Rose project at Drax in Yorkshire ( and another at Peterhead in Scotland (
These have both received money from the Government to conduct “Front End Engineering Design”(FEED) studies, the results of which will be publicly available and set out the detailed technical engineering, planning and financial issues before final investment decisions are made
( Technically we could be using CCS in the UK within the next five years. Whether or not we do is a political and financial question which remains open, although the Government has expressed support for the technology ("


23. "What cost assumptions are used to determine whether carbon capture technology makes any sense at all?" (golf charlie)

Dr Nial MacDowell (NMD): "The aim is to provide reliable, available and low carbon electricity. The cost assumptions that apply to CCS are the same as those which apply to other large capital projects, e.g., those that combine technology costs and technical performance and also typical econometric projections on fuel prices. This allows one to quantify the cost-per-MWh of the electricity generated by this technology. This data is then included in energy system modelling tools, which allows one to assess the value of a given technology to the energy system. On this basis, it has been repeatedly shown, by the IEA, the CCC, the IPCC and so forth, that CCS is absolutely vital to the least-cost transition to a low carbon economy."

22. "Are there better rocks to hide this CO2 under than others? Why?!" (Craig Gardener)

Michelle Bentham (MB): "Yes to store CO2 you need spaces between the rock grains that make the rock porous and permeable like a sponge. Good rocks for storage include sandstones. To stop the CO2 getting out of the storage rock‎ you need a rock that acts as a seal on top (low porosity and permeability) like a shale rock or mudstone."


21. "What is the total number of tonnes of CO2 deliberately manufactured every year, for commercial sale and/or use?" (golf charlie)

Prof Colin Snape (CS): "The use of CO2 in industrial processes and the food and drinks industry is tiny in relation to that emitted from power generation. In 2014, 32 gigatonnes of CO2 were emitted from power generation. This compares to only 50M tonnes used for enhanced oil recovery and the total industrial use for other applications is only about 20 M tonnes annually (0.1% of that from power plants)."

20. "From the fundamental science perspective, what are the biggest challenges for designing better CSS materials?" (Alex Forse)

CS: "There are many new materials that are being developed for CO2 capture that show great promise. The challenge is translating their performance from under ideal laboratory conditions to a capture plant with flue gas from power stations. Here the adsorbent needs to cope with water and acid gases, SOx and NOx, without compromising the performance for CO2. Also, for solid adsorbents, powders cannot be used so larger particle sizes are needed with very good mechanical strength and this also often leads to loss in performance."


19. "What is the accepted correct level of CO2 in the atmosphere?" (golf charlie)

CG: "The current concentration of CO­2 in the atmosphere is: 398 ppm (parts per million)

Preindustrial concentration was: 280 ppm

There is no 'accepted correct level' but the Intergovernmental Panel on Climate Change has published a set of ‘Representative Concentration Pathways’, based on the combined results of different climate models made by scientists. These pathways give scenarios showing how different atmospheric CO2 concentrations are likely to result in different increases in global average temperatures.

The politically agreed level is that this should not exceed 2°C ( Only scenarios achieving concentrations within 430-480 ppm by 2100 are associated with a greater than two thirds chance of reaching the 2°C target."


18. "If CCS is meant to decarbonise our energy - shouldn't we make sure none of the CO2 is used for enhanced oil recovery (EOR) down the line?" (Hanna Skarllson)

CG: "Using CO2 for EOR in the early days has helped to improve understanding of the processes and technologies involved in CCS. It also brings in some additional revenue that can help make CCS economically feasible in the absence of other policy mechanisms. The CCS infrastructure developed for EOR can then be used for continued CO2 storage in the field once it is no longer in active production. Looking forward we should indeed be aiming to phase out the use of fossil fuels. In the meantime we need to do everything possible to reduce the emissions from fossil fuels already being used. See for example:"


17. "What is the expected long term impact on the environment of the amine solvent carried over in the de-carbonised nitrogen flue gas?" (Vernon E)

NMD: "This question assumes that there will be amine solvent lost to the environment, and that amine-scrubbing is the only technology likely to be deployed. It is important to note that amines are regulated materials, with clear regulations limiting their emission. It is important also to note that amines are extensively used in a number of industrial sectors, for example, natural gas sweetening, so there are many, many decades of experience with their safe use. In order to mitigate against the release of amine to atmosphere, the decarbonised gas is first washed with water and subsequently dehydrated and passed through a bed of activated carbon to avoid any such emissions. Finally, other technology options, such as oxy- or pre-combustion or Ionic Liquids or Calcium Looping technologies avoid this problem altogether."


16. "Can we take old power plants and make them capture carbon? Or do you have to build it from new?" (Amy Wright)

CS: "Carbon capture needs to be fitted to new coal and gas power plants because they have high efficiencies, about 45 and 55-60%, respectively. Capturing CO2, compressing it for transportation in a pipeline and then injection into a geological formation for storage reduces the efficiency by about 10 percentage points. Therefore, it is not cost effective deploying CCS on old coal-fired power plant operating with only about 37% efficiency."


15. "The papers say that this new nuclear power station will get £92.50 for each megawatt. What is the current price for gas with CCS installed? What is the predicted price for gas with CCS when Hinkley C is finished in 2025?" (Doug Riley)

NMD: "The cost of CCS for any technology depends on the cost of capital (WACC) and also fuel costs, in addition to the cost of the underlying plant. The Department of Energy & Climate Change’s recent “cost of generation” report suggests that gas-CCS (post-combustion capture) will cost approximately £95/MWh and coal-CCS (oxy-combustion capture) will cost approximately £107/MWh. It is important to note that these are first of a kind costs (FOAK), and based on experience from the Boundary Dam project in Canada. One might expect as much as a 30% cost reduction in moving from the 1st to 2nd generation of plants. It is also worth noting that these costs (£95 – 107/MWh) compare well with other, mature forms of low carbon power, with onshore and offshore wind costing in the range of £99-120/MWh."


14. "CO2 has been used for years to extract more oil/gas from "conventional wells" but no research has been done to see if these leak. This would seem to me to be the very first avenue to persue if this costly "solution" was used. As a geologist I think that leakage would be immediate and total so a useless solution to a non-problem." (John Marshall)

MB: "Agreed, existing oil and gas wells are a risk to storage integrity. There has been a huge amount of research on well integrity. This forms part of the work needed before a storage permit is granted. In the UK, these permits will be issued by the DECC (Department of Energy & Climate Change)."


13. "Is CCS for gas the same as CCS for coal? The Chinese are building lots of coal stations, are they building them with CCS?" (Jayne Riley)

CS: "In principle, yes, the technology is the same. There is less CO2 produced from gas power stations so the costs per tonne of CO2 are higher for gas from coal. However, the increase in the cost on electricity for deploying CCS with gas is lower because of the smaller amount of CO2 per unit of electrical energy (KW hour).

CCS is not a proven technology so all the new coal-fired power stations in China have been built without CCS. It will be essential to deploy CCS to this fleet if the technology is going to make a significant impact on reducing global CO2 emissions from power stations."


12. "Where is the bottleneck in the CCS supply chain?" (@SGI_london)

CS: "There are no bottlenecks or showstoppers as such regarding the technology. CCS can be implemented and a whole-chain demonstration is working at a power plant in Canada where the captured CO2 is used for enhanced oil recovery. Clearly, demonstrations will lead to improvements in the technology but the major issue is around how these large projects are financed, and the policy incentives needed."


11. "Where are we going to store the carbon? And in what form? Can we do something more that just bottle it up and hide it away? I'd like some for my greenhouse!" (Richard Regan)

MB: "CO2 can be stored in geological layers deep in the subsurface (below depth of 800 m) where the earth’s pressure and temperature means that CO2 is a dense fluid which occupies much less space than it would on the surface. The CO2 is injected (via a deep well also known as a borehole) into the spaces between the rock grains known as pores in a geological formation known as a reservoir (often a sandstone). It becomes trapped underneath an impermeable layer of rock known as a caprock (shale or mudstone). This reservoir caprock pair is the same scenario that has trapped natural oil and gas for millions of years. The correct geology can be found in sedimentary basins all over the world ( p9). CO2 can be used in other ways e.g. in the drink industry, in fire extinguishers, for recovering oil and in greenhouses. Unfortunately these industries do not need the quantities of CO2 required to reduce the impact of climate change and ocean acidification."


10. "Isn't CCS more important for heavy industry like steel, aluminium, cement? Is that happening at all?" (James Dennis)

NMD: "CCS is certainly important for heavy industry – and there is increasing focus on understanding how CCS can best be deployed to these sectors. However, the primary focus remains with the power sector, owing to their role as largest point source of CO2."


9. "Will it cost less to decarbonise if we don't use CCS for the UK? How about the world?" (@sandbagorguk)

NMD: " No. It will cost very substantially more. The ETI have comprehensively shown that the absence of CCS will add ~ £30 Billion to the cost of decarbonisation in the UK. The same has been observed by the IEA for other parts of the world. CCS is unambiguously a key component of any least-cost pathway to a low carbon economy."


8. "Could we use all our CO2 instead of injecting it into geological storage?" (@sandbagorguk)

CG: "There is certainly the potential to use some of the CO2 from industrial processes, for example for use as a growth enhancer in glasshouse crops, as a feedstock for other industrial processes (such as fertiliser manufacturing) or in food (carbonated drinks industry) and indeed this is already done to some extent on a small scale. However, the CO2 still requires treatment to clean other compounds from flue gases (which requires energy), and, especially in the food sector, it must be treated to a very high level of purity. There is a growing body of research looking into opportunities for larger scale carbon capture and utilisation but it is very unlikely that these processes could use CO2 on a scale to match the potential for geological storage – it is more likely to be as an additional option. See for example:"


7. "Can you put CCS on taxis and lorries?" (Simon Fitzpatrick)

CS: "No, CCS is only suitable for large 'point sources' emitting CO2, since after the CO2 is captured it then has to be compressed to go into a pipeline for transportation to the geological storage site. Therefore, CO2 capture cannot be carried out on vehicles."


6. "What is going to make a power plant owner spend the extra money on CCS if it's so expensive?" (Ray Jones)

NMD: "The first point to bear in mind is that CCS is not “so expensive”. Yes, it is, unquestionably, more expensive than unabated fossil fuels, but it is on par with the already mature wind-based power generation sector.

We will not transition to a low carbon economy at zero cost – otherwise our market-driven economy would have provided this already. So to have this discussion, we first need to agree that transitioning to a low carbon economy is worth doing. Then, the rational path is the least cost transition. It has been shown, again and again, that CCS is key to any least cost transition – without CCS, the costs of this transition are at least twice as high.

The next point that is important is the value provided to our society by reliable access to energy – electricity in this case. It is vital to understand that electricity systems don’t just need electrons – they need a variety of other services as well, typically termed ancillary services, which amongst other things ensure that the electricity is available at the point of use at the right frequency, so your appliance works. This is a service that CCS can uniquely provide amongst all other, currently available, clean power generators.

This then brings us to a place where we need available, reliable, low carbon energy. In order to incentivise this, we need a number of regulatory tools or instruments, such as a carbon price and/or an emissions performance standard (EPS) in order to stimulate the growth of this industry – similarly to what is currently provided under electricity market reform (EMR) in the UK."

5. "What tests have been done to make sure any CO2 we store doesn't escape? Have we tested storing large volumes?" (Michael Rodriguez)

MB: "We have a range of tools to check the CO2 remains in the subsurface. These target different parts of the storage complex. In the reservoir we can use geophysics such as seismic surveys to detect CO2 and verify it is not in the overburden (the earth directly above the storage complex). Tools in boreholes can check pressure, chemistry and movement. On the surface we can measure gravity changes, surface uplift and detect gas should it leak. These tools have been tested widely at demonstration sites such as Sleipner, In Salah and Ketzin."

4. "Presumably there are different ways of capturing carbon. Is there one obvious method that is 'better' than others?" (Hilary Jayne)

NMD: "Yes. There are a few different ways, but they differ in the details. Simply, you produce CO2 as a result of combusting fossil fuels in air – combining carbon with oxygen and producing an exhaust gas primarily of N2 and CO2 (with some O2, H2O and other compounds too).

The three main ways of capturing CO2 are:
a) post-combustion capture: this is removing the CO2 from the N2 and can be achieved with liquids, solids or even membranes.

b) oxy-combustion capture: this is burning the fuel in a high O2 environment so that the exhaust gas is mainly CO2, with ~ 5-7% each of O2, N2, and H2O. These compounds can then be removed relatively easily from the exhaust.

c) pre-combustion capture: this is removing the carbon from the fuel before it is burned, leaving only a H2 rich gas to be burned, which produces only H2O.

So none of the technologies are better or worse. Each has its own pros and cons, depending on the CO2 source."


3. "We should move away from fossil fuels. CCS is only a stopgap. Is it worth putting all this money into something that is only a stopgap?" (Norman Parker)

CG: "It is true that we need to move away from fossil fuels but the shift to renewable energy will not happen overnight – energy systems worldwide are still dominated by fossil fuels. CCS could help to significantly reduce the greenhouse gas emissions from fossil fuel energy in the short term, while we build up a decarbonised system. The costs need to be weighed against the urgency with which we should view action on climate change."

NMD: "This is a fair question. At some point, we will use up all the fossil fuels on the planet. However, this will not be any time soon – or even this century. To my mind, there is no question that, for reasons of energy security and cost, we will continue to rely heavily on fossil fuels beyond the end of the century. However, to continue to exploit fossil fuels as we have done in the past will unquestionably be a disaster for the planet. CCS is key to enabling the environmentally benign utilisation of fossil energy."

2. "Why are we even trying to make coal clean? We know it's dirty." (Dan Curtis)

CS: "Globally, over 35% of electricity generation is from coal and much of the equipment for this is very modern, especially in China. Therefore, if we are to decarbonise electricity production, it is essential that CCS is deployed on such modern plants that have a lifetime of approximately 40 years."

1. "The planet has been capturing and storing CO2 for hundreds of millions of years, the storage facilities do not leak and the CO2 is easily recoverable, the system is 100% tested and safe. Why are we spending money on an untested alternative?" (Dung)

MB: "It is true the planet has been very efficient is sequestering CO2 in its oceans and rocks. Unfortunately the human race is emitting so much CO2 that these systems have become unbalanced, the oceans are becoming more acidic, and the planet is warming through the greenhouse effect. These things are not safe, unless we want to live with the impacts of acidic oceans and a hotter climate we need to either reduce the CO2 we emit or stop the CO2 entering the atmosphere. Carbon Capture and Storage (CCS) is a tested technology ( for reducing our CO2 emissions, which allows us to still provide energy while developing alternatives such as renewable energy. CCS is the only way some industrial sources of CO2 such as cement works can reduce their CO2 emissions."



Our Q&As answer the questions people put, which may mean that some parts of a subject are covered well and others not. If there is an issue that you think is not tackled, you are welcome to send a follow up question to our energy panel