Climate News Network

Carbon capture could be costly and risky

February 17, 2016, by Tim Radford

Power station emissions dominate the view from the city of Leeds in West Yorkshire, UK.
Image: idb1979 via Flickr

Attempts to remove carbon dioxide from the atmosphere and store it safely are all potentially costly gambles with the current technology, scientists say.

LONDON, 17 February, 2016 – There’s bad news for those who think that carbon dioxide can be removed from the atmosphere and stored deep in the Earth’s rocks.

Even if carbon capture is possible, sequestration in the rocks is fraught because the gas can find multiple ways to escape, according to a report by a team from Penn State University, US, in the International Journal of Greenhouse Gas Control.

Carbon dioxide is not the only greenhouse gas, but it is the one that drives global warming. It escapes from power station chimneys and motor exhausts.

Back in the 18th century, the air contained 280 parts of CO2 per million, but now the level has just reached 400 parts per million. In the same period, the average global temperature has risen by 1°C and will go on rising, to make climate change an increasing hazard.

Switch to renewables

Last December, 195 world leaders agreed in Paris to take action aimed at containing warming to – if possible – 1.5°C.

Climate scientists warn that the world must switch to solar power, wind and other renewable sources.

But some think that if the exhaust emissions could be trapped and stored, humans would be able to get a bit more value from their fossil fuel investments. Others see it as the only way of avoiding 2°C of warning − the agreed international safety limit prior to the Paris climate summit.

The problem is that nobody is confident that carbon can be captured on a sufficient scale.

“Removal of CO2 will be expensive and is currently
unproven at the scale needed – so it would be much
better to reduce emissions as rapidly as possible”

Some projects have been abandoned, and others suggest that the problem is that not enough has been spent on the research.

But the Penn State team looked at a different aspect: whether CO2 could be buried and forgotten. So they tested laboratory reactions that involve sandstone and limestone – two of the sedimentary rocks found most often in geological strata – and water and carbon dioxide.

They tried cementing the greenhouse gas in limestone, and in sandstone. And then they watched. Rocks are porous, and subterranean water tends to dissolve salts. If the water meets the CO2, the gas will make the saltwater more acid, and the increasingly acidic water will start to dissolve the rocks around it.

The scientists reasoned that the trapped gas − with a little help from natural chemistry − could find its way back to the surface anyway. So it represents an uncertain strategy.

“We were interested in examining these rocks because they are widely found underground,” says one of the report’s authors, Li Li, a petroleum and natural gas engineer.

“Even if it doesn’t escape to the Earth’s surface, there are concerns that it may leak into groundwater drinking aquifers.”

Environmental risks

But any attempt to remove CO2 from the atmosphere presents difficulties, according to Phil Williamson, an environmental scientist at the University of East Anglia, UK. He writes in Nature journal that there are environmental risks to almost any potential solution.

This remains true whether the answer is deep burial; investment in bioenergy crops; tree plantations; the addition of crushed silicate rocks to the soil to chemically absorb CO2; the spraying of clouds to make rain more alkaline and react with the carbon dioxide; the fertilisation of the oceans to promote plant growth and soak up more carbon; or even the use of straw and timber for building.

All involve massive expense, some of them remove land urgently needed for crops, and every single solution could have some troubling knock-on effect that disturbs the natural ecosystems on which all life depends.

The way to keep to the Paris Agreement, Dr Williamson says, is to begin drastically reducing fossil fuel use.

He says: “If rapid cuts are not made, then significant CO2 removal will need to begin in less than four years, with 20 billion tonnes a year removed annually by 2100 to keep the global temperature increase well below 2°C.

“But removal will be expensive and is currently unproven at the scale needed – so it would be much better to reduce emissions as rapidly as possible.” – Climate News Network

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  • Tim – thanks for this new report further weakening the credibility of the geological storage of CO2.
    It adds to the largest demerit – which in my view is the sheer scale of expensive infrastructure needed for it to be of significant effect. This is shown in the fact that to sequester just 10% of the annual anthro-CO2 output, the plant and pipelines required would be roughly equal in scale to those of the oil industry’s entire global heritage – which has taken most of a century to develop.

    There is a further critical demerit which has yet to be publicly discussed, but which will I guess lead to outright public rejection of the geological CO2 storage option when it is recognized. It concerns the multiple HP liquid CO2 pipelines that would have to be laid in every major country between the power stations and the most suitable areas of geology, plus the fact that most towns and cities have been established in river valleys, plus the fact that CO2 is heavier than air.

    Consider – if a HP liquid CO2 pipeline were laid uphill of say Reading, Swindon or Bath, with pumping stations at say 20-mile intervals, it would take only a small Daesh team armed with nothing more than spades to dig down to it one night when a gentle breeze is blowing towards the target city, and to plant a small bomb with mobile phone detonation, for the entire high pressure CO2 contents of the pipeline to flow down over the sleeping city. Besides being transparent and odourless, at sufficient concentration CO2 is lethal by asphyxiation within a few minutes, implying a potentially very large number of victims.

    I suspect that HMG was recently advised of this threat and, coming on top of the string of known demerits, it was sufficient to cause the otherwise unexplained cancellation of the £1.0bn CCS competition. I hope you might make enquiries to see if this can be verified – not least because CCS into geology remains a necessary fig-leaf for the present official “Denial of Urgency” over ending fossil fuel dependence.

    However, I would differ with the scientists quoted above in terms of policy – where I can claim to have no less expertise than they –

    First, the title ‘Carbon Capture and Storage’ is basically misleading when applied to this option and no scientist should use it – Carbon in its natural form as charcoal is quite inert and very useful, especially under the climate predicament, as a low-cost soil-moisture regulator and fertility enhancer. CO2 not so inert and is by comparison highly lethal in the intended liquefied mode, and this difference should be expressed by using the acronym ‘CO2CS’ or perhaps ‘CDCS.’

    Second, with the UK’s ‘joint goal’ having become the ‘Paris Outcome’ of “Net-zero emissions in the second half of the century” it seems simply bizarre for scientists to be now pushing Emissions Control at the expense of the option of Carbon Recovery. I doubt they can be unaware of the scale of the climate predicament, which is not limited to our ‘phase-out’ emissions but includes the inevitable timelagged warming for emissions since the late 70s, plus the loss of the cooling fossil-sulphate parasol, plus the ongoing acceleration of the seven non-linear major interactive feedbacks on AGW, which will not be fully halted by anything less than the restoration of the pre-industrial temperature.

    From this perspective it seems very clear that we have to apply both Emissions Control and Carbon Recovery as rapidly as humanely possible. Scientists disputing this without offering a reasoned refutation seems really unhelpful.

    Third, while I would agree with the assertion that all Carbon Recovery techniques could have downsides, for some that would plainly depend on whether they are done well or badly – and that is an issue of the quality of governance. Having studied the option of “Native Coppice Forestry for Biochar and Coproduct Methanol” over the last 25 years, I’ve yet to find any intrinsic demerits, and have found a string of globally significant merits. Of these the most obvious lies in the option’s appropriate title of:
    “Carbon Recovery for Food Security”.

    The routine critique of this option is of land-use displacing farming, but this was refuted by an under-reported joint study by WWF & WRI in 2012 which looked at land area available for afforestation globally without impacting farmland (a small fraction of agro-forestry, woodlots etc was included). It found that about 1.6GHa.s or ~4.0bn acres is available globally, which under a good-case calculation regarding lead time to full flow by 2045, would potentially cleanse the atmosphere of anthro-CO2 during this century.

    Given that this CCS option is at least partly self-funding through its twin revenue streams and serves a number of critical policy goals, for scientists to be dissing it without a serious rationale for doing so again seems very unhelpful. If they are willing and able to provide such a rational I should of course be interested to see it.

    Regards,
    Lewis

  • The carbon capture solution is obvious. Once algae growing in sealed bioreactors is perfected, grow gigatons of algae in arid areas or in the far northern summer. Use the biodiesel for transportation and bury and cap the gigatons of algal cell walls (mostly cellulose) in huge lignite mountains. The mountains will be stable for several thousand years, assuming that our descendants don’t dig the carbon up again.

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