Could we store carbon in pools of brine underneath the seabed?

Ecological catastrophy
Ecological catastrophy

It’s one of the more ambitious ideas in terms of dealing with carbon dioxide - burying it in pools of salty water beneath the seabed.

Such an idea - if it worked - has the potential to safely store carbon dioxide for thousands of years.

Researchers believe that pipes could one day carry CO₂ from the earth's atmosphere into these aquifers, where it will be stored harmlessly, potentially forever - and pilot plants have been built to study the idea.

A new study from the University of Bath has shed new light on the way saline solutions act in deep geological formations (known as aquifers).

In an ideal world, the combination of seawater and CO₂ under pressure will result in the formation of rock, though it is more likely that the blend will retain its liquid form.

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Co-author Professor Philip Salmon, from the Department of Physics says, "Providing the rock above the solution is fault-free and impermeable, the CO₂ will stay there.

The researchers observed saline solutions under conditions of pressure and temperatures that mimic the conditions found in deep aquifers.

Their 'neutron diffraction' technique allowed them to examine saline solutions in more extreme conditions than ever before.

Previous experimental efforts to find answers have failed because the solution, under extreme conditions, is highly corrosive and destroys the lab equipment it's contained within before results are yielded.

Co-author Dr Anita Zeidler from the Department of Physics says, "Being able to hold these solutions without the apparatus falling to pieces was a big challenge.

"We overcame them through the design of high-pressure apparatus and a judicious choice of containment materials."

Professor Salmon said: "Our experiments show that by using neutron diffraction, you can see how the salt ions and water molecules interact under quite extreme conditions of heat and pressure. Next, we'll be attempting to dissolve carbon dioxide into the saline solutions.

“The results from these experiments will inform models on carbon sequestration mechanisms, with the end-goal being to find a way to safely sequester carbon dioxide in deep-sea aquifers."

Technology will play an increasing part in dealing with carbon emissions in coming years, experts believe.

Read more: A 1988 warning about climate change was mostly right

A new report by the UN's Intergovernmental Panel on Climate Change (IPCC) has suggested various scenarios for climate change - and many rely on technology to ‘capture’ carbon from the atmosphere.

Carbon removal relies on removing existing CO2 from the atmopshere, either by planting trees, or using technology.

The report says, “Most strong-mitigation scenarios assume – in addition to emissions reductions – some form of carbon 51 dioxide removal (CDR) – anthropogenic activities that remove CO2 from the atmosphere and durably store it 52 in geological, terrestrial, or ocean reservoirs, or in products.”

By 2050, America alone may need to remove one-third of its current annual emissions per year under some of the scenarios in the IPCC report.

Several companies are already investing in technologies including 'direct air capture', and attracting hundreds of millions of dollars in investment, according to Quartz.

But the cost of 'direct air capture' remains high ($600 per ton of CO2).

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Simon Richardson, co-director of the Institute for Carbon Removal Law and Policy at American University said, “Doing the work today to sort out how to responsibly and sustainably remove carbon dioxide from the atmosphere is now essential.”

Even if every country cut CO2 emissions almost completely now, the world is still likely to warm to 1.6C before dropping again, ABC News reports.

Getting back down again, would require either massive reforestations or technology to remove carbon dioxide from the atmosphere.

Michelle You, co-founder and CEO of Supercritical points out in an interview with Energy Digital that to limit temperature rises below 1.5C will require the world to remove at least eight billion tons of carbon dioxide a year by 2050.

She says, “Traditional carbon offsets are part of the problem since a tonne of carbon offsetted is still a tonne of carbon in the sky.

"The only legitimate route to net zero is through carbon removal offsets - such as direct air capture and bio-oil sequestration - which work by actively removing carbon from the atmosphere and storing it permanently.”

More controversially, the report also looks at solar radiation modification (SRM) technologies which aim to mitigate climate change by spraying particles into the air.

The report highlights problems with the technology such as knock-on effects at the regional or seasonal level.

The idea of ‘solar geoengineering’ or solar radiation modification (SRM) is controversial, mimicking the world-chilling effects of huge volcanic eruptions.

Some scientists have suggested that such technology could be used as a ‘stop gap’ to reduce temperatures while measures to limit CO2 emissions are put in place.

But the report warns that withdrawing SRM technology could lead to a rapid rise in temperatures.

The IPCC previously wrote, ‘Uncertainties surrounding solar radiation modification (SRM) measures constrain their potential deployment. These uncertainties include: technological immaturity; limited physical understanding about their effectiveness to limit global warming; and a weak capacity to govern, legitimize, and scale such measures.”

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