Carbon Capture and Storage
In pursuit of its “green” energy strategy, it is clear that the British government is desperate to find someone to spend £1 billon on a project to build a near full-scale “Carbon Capture and Storage” (CCS) plant. Various companies owning electricity generating plant have been approached. All have declined to pursue this nonsensical Will-o-the-wisp idea which successive ministers and impractical climatologists at the Department of Energy and Climate Change (DECC) imagine will allow them to keep coal plants running and meet the 2020 and 2050 emissions targets which the Blair government imposed on Britain through the EU and its own Climate Change Act 2008 (see post of June 1st 2011).
Before going any further let’s be clear: no British parliament can bind its successor, so any future government can easily – in a few days – repeal any or all parts of the CCA 2008, and rid Britain of emissions targets which can have absolutely no bearing on Britain’s or the world’s climate now or in the future, but will impoverish our people.
Carbon Capture and Storage
What does this amount to? The carbon referred to is in fact carbon dioxide (CO2), which is 3.67 times as heavy as the carbon from which it comes. So looked at from the point of view of someone circling the Earth in a satellite, what is proposed is digging carbon (as coal) out of the ground, combining it chemically with oxygen from the atmosphere (by burning it) and then burying it somewhere below the earth’s surface. Truly such an observer would ask: “Is it a religious ceremony or are they just plain mad?”
The answer is both in fact: climate change people have all the characteristics of adherents to a new religion of which history has many examples – the blindness of belief, the priesthood with its own hierarchy, the grip on public money, even excommunication procedures when non-believers and apostates are excluded from access to public money (e.g. grants from the DECC and the Research Councils).
Descriptions of CCS systems
Descriptions of putative CCS systems in the broadsheet newspapers and magazines like the Economist avoid including the costs and numbers largely because they haven’t been worked out. For example the London Times business section of March 29 2012 published a description summarised as follows for a CCS system attached to a coal-fired electricity power station:
(1) “Instead of being released into the atmosphere CO2 is captured and compressed.” (Questions: how “captured” and how “compressed” and to what extent?)
(2) “CO2 is pumped and injected into depleted oil fields to recover the last drops of oil from the North Sea. This is a well practised technique using steam, or nitrogen or CO2, but mainly on a scale of a few thousand tonnes of CO2/water per well for a few years.” (Question: what happens to the CO2 after it has been pumped into the depleted reservoir? If water is used instead, it diffuses into surrounding earth and sea and is easily tracked, but where is CO2 supposed to go?)
(3) “Most of the CO2 is intended to be pumped into or through porous sandstone rock to cavities which previously held hydrocarbons.” (Question: how is this supposed to happen? There is all the difference in the world between drilling a hole to let already pressurised natural gas flow to the surface from myriads of cavities, and forcing liquefied CO2 into these same cavities, which will not be vacuums, but will already contain gas at the local pressure under the North Sea – 30 atmospheres typically.)
As in all energy and process engineering matters, numbers dominate. What may be possible for a pilot-scale coal station of say 1 MegaWatt (power for about 100 homes) may be totally impracticable on the scale needed to have a noticeable effect on the UK’s emissions. Despite the assertions of sundry BBC commentators, none of the processes involved have been operated on anything like the scale required to have any significant impact on Britain’s emissions.
The Drax-scale case
The Drax coal-fired power station is rated at 4 GW and produces around 29 TeraWatt hours per year of electricity (about 8% of UK current output) and thus 27 million tonnes of CO2 per year (about 5% of UK emissions). This amounts to 70,000 tonnes per day occupying 35 million cubic metres as a gas (a volume roughly 90 times the volume of the Royal Albert Hall). This gigantic efflux is currently put into the atmosphere through 50-100 metre high vertical pipes along with four times this amount of Nitrogen (N2) and, depending on the hydrogen content of the coal, possibly as much as 5 million metres of water vapour.
If CO2 is to be stored as described, around 66 million tonnes per year of nitrogen will have to be separated from it. For 40 years the natural limit of plants which process nitrogen to make ammonia is around 5 million tonnes per year, corresponding to about 4.2 million tonnes of nitrogen.
So on the Drax scale, we would need a nitrogen-CO2 separation plant 15 times bigger than the largest ammonia plant ever built and several times the size of the power station itself. The costs of operating it and the associated CO2 compression will dramatically reduce the electrical output of its power station and hugely increase the unit cost of the net electricity produced.
Separation of CO2 from Nitrogen
As an extremely inert gas, CO2 is non-reactive with most things. It is however absorbed by liquid ethanolamine at one temperature-pressure combination and desorbed at another. This makes an absorption column a possible candidate though never tried on the Drax scale or anything like it
Compression and storage of CO2
To store below the seabed CO2 will have to be pressurised to at least 40 atmospheres, probably 50, on the Earth’s surface where the electricity stations are. At these pressures and around 16 oC temperatures, CO2 will in any case be in liquid form, which is the only way even a tenth of the vast quantities from a Drax-scale power station could be piped to storage.
As calculated in a recent article by Bush and MacDonald, the Drax output would require 14 million cubic metres of secure 50 bar storage every year (equivalent to 38,000 m3 per day). This volume corresponds to 18,000 km of one metre diameter pipe every year, enough to go four times around the British Isles (which would be very good for our under-used steel plants). If the project tries to bury this amount in rock 600-1,000 metres below the North Sea surface, this would be equivalent to filling 14 billion one-litre milk bottles every year and ensuring they didn’t leak – a virtually impossible task on even one-thousandth of this scale.
Oil and Gas leakages
The present leak of hydrocarbon gases from the Elgin well in the North Sea, operated by the French company Total, should alert even the DECC and Prime Minister Cameron of the sheer folly of CCS. Even though the leakage is tiny compared with the Drax-scale CO2 flows, and the gas can if necessary be burnt controllably, the rig has had to be evacuated and air-sea exclusion zones declared. Total have still not after a month located the source of the leak, but believe from its maps and calculations that it is from a rock fracture 4,000 metres down.
The much more serious BP Deepwater Horizon (Macondo) oil spill in 2010 in the Gulf of Mexico flowed unabated for 3 months. To stop it, required a relief well to be sunk 5,000 metres to take the oil to the surface in a controlled way. At its peak, it is estimated that 9,900 m3 per day leaked, only about one quarter of the equivalent volume of liquid CO2 produced every day on the Drax scale. Altogether 780,000 m3 of oil were released from the Macondo well before the leak could be stopped. This required all of BP’s world-wide resources to achieve but is equivalent to only 5.5% of Drax’s annual production of CO2 in equivalent liquid form.
Consequences of undersea CO2 leakages
These will depend on the size of the leak of course, but it should be noted that unlike oil, CO2 would come to the surface as gigantic geysers of cold gas, propelled by their 10-fold expansion from the liquid state 500-600 metres below and their subsequent 50-fold expansion as they rise to the surface. Unlike hydrocarbon gas, CO2 flows cannot be controlled by burning.
A CO2 leak on the Macondo scale – 10,000 m3 per day of liquid would give 5 million m3 per day of gas. Without 50-100 metre high chimney stacks, and being heavier than air, this is likely to create a large, suffocating blanket of CO2, 50 metres thick say, covering an additional area of about 10 hectares (25 acres) each day the leak persists. At 10% dilution, this would pose real risks of suffocation to people working on the neighbouring North Sea rigs as well as aircraft diversions and delays across parts of the North Sea, if the leak persisted for 3 months or more.
The European Union Dimension
Should the British government (and it will be the government – no private money will touch it as we have seen) ever succeeds at gigantic cost to the British taxpayer in commissioning a system to deliver even one-tenth of the Drax scale CO2 into storage, the EU has announced that such storage cannot, under EU rules be reserved for British CO2 – it has to be open to all 27 EU countries. This could have the supremely beneficial effect of finally propelling Britain out of the EU – but it’s not necessary to engage in CCS follies to achieve that. The £10 million cost of a referendum will do.
What should be done?
- All professional engineers, seeing the figures above and in the cited references should by emailing Prime Minister Cameron and Chancellor of the Exchequer George Osborne on the government website, express their horror at the madness of spending any more money on CCS.
- The government should instead use the £1 billion currently earmarked for CCS to establish a new British Nuclear Corporation tasked with building up to 10 new nuclear reactors over the next 25 years using the now approved Westinghouse AP 1000 reactor designs on the sites of the 6 old Magnox nuclear electricity stations, which EDF, through British Energy, currently owns, but isn’t going to use itself.
 For a full discussion of this and all other relevant issues see “Averting Catastrophe: Ensuring the security and affordability of Britain’s Energy Supplies 2011-2050” by S F Bush and D R MacDonald on this website.
 Often referred to as Enhanced Oil Recovery (EOR) and used in the USA since the 1970s.
 This is the KBR plant in Egypt which is rated at 5 million tonnes of ammonia per year at full output.
 Of course you can reduce the scale by splitting the CO2-N2 streams, but even by a factor of 10, the flows will still be gigantic (from figures above).
 “Squaring the Circle” in The Chemical Engineer, October 2011, pages 30-34. This was awarded the Institution of Chemical Engineers’ Hanson Medal as best paper published in 2011.