Carbon capture and storage: off the North Yorkshire coast? Pictures: co2crc.com.auCarbon capture is a way to radically reduce greenhouse gas emissions – and the Yorkshire coast could play a key part, explains Liam Herringshaw
As a palaeontologist specialising in old, weird sea-life, I have never been very useful. Good company but of little practical value, my headstone will say.
In the last few months, though, this has begun to change. By a combination of opportunity and availability, I have found suddenly myself working in two very topical areas of applied Earth science: shale gas, and carbon capture and storage.
Shale gas is the more media-bewitching of the two, perhaps because it allows journalists to use the word “fracking” with schoolboy abandon. Carbon capture and storage (or CCS), however, is a bit less easily dramatised, so it tends to get less attention. This is a pity, because it is potentially very important to our energy future, and Yorkshire looks set to play a key role in its development.
Recent cold winters and a chilly spring should make us think about how best to power Britain. Only a numpty would argue against us moving in a greener direction, but the cost, complexity and politics of renewables means we won’t be weaned off fossil fuels any time soon. An inspection of the sources of UK daily power consumption shows just far we have to go.
As a consequence, stepping stones are needed to reduce our greenhouse gas emissions. CCS is one possibility, and as its goal is the permanent geological storage of carbon dioxide, this is a step in which the stones are critical.
How CSS works
The basic premise of CCS is as follows:
1. Fit chemical filters to power stations and other major emitters, capturing CO2 before it is emitted into the atmosphere 2. Condense the captured CO2 and use gas pipelines to transport it out to the North Sea 3. Inject the CO2 into rock formations deep beneath the sea, from which it cannot escape.
Hey presto! A major shrinkage in our carbon footprint.
A vast volume of storage space is present in the rocks beneath the North Sea; huge quantities of CO2 could be sequestered in networks of tiny pore spaces. One of the remaining uncertainties, though – and the one in which I have become involved in trying to understand – is how geological variabilities affect where the carbon dioxide goes once it is injected into the rocks.
Sandstones make the best prospects, as not only are they porous, but the pores are interconnected. This permeability enables the injected carbon dioxide to move as a plume through the rock and fill the reservoir. If the sandstone is a saline aquifer – a reservoir full of extremely salty brine – the CO2 will begin to dissolve into the saltwater. Eventually, the CO2 will become trapped in the pore spaces and precipitate as a cement in between the grains.
Trapping CO2 in sandstone
This isn’t a fast process, so you need to know the injected carbon dioxide will not only fill the chosen reservoir but stay there. When choosing a geological site for storage then, you need large bodies of sandstones that aren’t faulted or fractured. You also need them to be overlain by an impermeable cap rock.
Why the Yorkshire coast is ideal
Conveniently for the White Rose project then, the Triassic sandstones off the East Yorkshire coast look very promising indeed. They were deposited by desert rivers about 250 million years ago, when Britain lay in much warmer climes. Eventually the desert sands got buried and turned into sandstone, and, later on, folded by tectonic forces into gentle domes.
The sandstones have few faults in them, are often filled with brine, and are capped by impermeable salts or shales, making them extremely attractive as CCS reservoirs. The Crown Estate, which owns the UK seabed out to a distance of 12 nautical miles* and holds the rights for carbon storage out to the continental shelf, has recognized this. In a statement issued a few weeks before the Budget, they gave the National Grid permission to look into storing CO2 in a saline aquifer 70 km offshore of Filey Bay.
Exploratory drilling into the reservoir could start as early as this month. With the North Sea gas pipeline coming onshore at Easington, and the Drax power station employing carbon capture technology, Yorkshire’s CCS elements begin to come together promisingly.
Doing all this isn’t going to be cheap, but development costs might be offset by selling some of the captured CO2 to petroleum companies
Doing all this isn’t going to be cheap, but development costs might be offset by selling some of the captured CO2 to petroleum companies. This might sound a bit odd, but injecting it into petroleum reservoirs is a proven method of enhanced oil recovery (EOR). It could provide two years’ worth of UK oil supplies from existing fields, and would be lower impact than opening up new ones.
Not unreasonably, some people are sceptical of CCS, arguing that it will just allow the continued exploitation of fossil fuels, without facilitating a move towards greener energy. They could be right; I think it depends on political will to put a long-term renewable energy plan in place. As discussed in YorkMix previously, there may be ways to make the White Rose Project greener, so Yorkshire’s role in powering Britain cleanly could be even more important than it already looks to be.
This would send out a strong message, especially if UK interest in shale gas takes off. But that’s another fracking story.
*and right down to the centre of the Earth, which leads me to imagine the Queen sitting in Buckingham Palace of an evening, looking at a seismic cross-section of the British Isles, planning how best to imitate Jules Verne.
Carbon capture is a way to radically reduce greenhouse gas emissions – and the Yorkshire coast could play a key part, explains Liam Herringshaw