A range of greenhouse gas removal technologies may be necessary if we’re to reach Net Zero by 2050. In the second of our two-part geoengineering feature, Eoin Redahan looks to the sea, the sun, and mineral weathering, and at the ethical concerns such technologies raise. Missed Part One? Find it here.


‘Water, water, everywhere, nor any drop to drink.’

These famous words from Samuel Taylor Coleridge’s Rime of the Ancient Mariner aren’t the only famous part of his epic poem. The term albatross around one’s neck comes from it too.

After shooting a friendly albatross at sea, the poem’s narrator was forced by the ship’s crew to wear the dead creature around his neck – and grievous luck was to follow. Well, our blue planet has an albatross around its neck in the form of climate change.

Perhaps the solution to it lies all around us – water, water, everywhere…

An ocean of potential

In theory, we can use our oceans to pull CO2 from the air on an enormous scale. All it may take is clever intervention – potentially ruinous, albatross-shooting intervention.

Nevertheless, the World Economic Forum lays out the tantalising potential. ‘Ocean-based CO2 removal can help us achieve “net negative emissions” as the seas hold 50 times more carbon than the atmosphere,’ it says.

‘The ocean [is] a sink for nearly one third of anthropogenic carbon emissions and more than 90% of the resulting heat… If we are going to manage atmospheric CO2 levels to our advantage, we will need to leverage the ocean’s existing ability to govern the global carbon cycle.’

Frontier has targeted the development of scalable sources of alkalinity. The reasoning behind it is that with CO2 being an acidic molecule, rising CO2 concentrations could be neutralised through alkalinity. It has mentioned using mine tailings to remove up to 0.5 gigatonnes of CO2 from the air each year; but the major caveat here is that it needs to be done safely.

Planetary Technologies has ventured into this space armed, essentially, with a bicarbonate of baking soda that could draw in CO2 and sequester it for millenia.

The company explains its process: ‘We start by carefully extracting key parts of the mine tailings including recovering battery metals (like nickel and cobalt) and silica (sand) and then take the remaining purified metal salt solution into a special electrolyser. There, using clean, renewable electricity, the salt and water are split to make hydrogen (a clean, emissions-free fuel), and a pure alkaline hydroxide.

‘It’s from this point that we transport the bulk alkaline materials to our ocean outfalls site where the alkalinity is introduced to the surface ocean that then draws in CO2, sequestering it as already abundant bicarbonate and carbonate ions in seawater.’

So, by decreasing the acidity of the ocean, it would have a greater capacity to absorb CO2 from the air. The key, however, is to reduce this to a viable price point.

>> Want to read about iron fertilisation in our oceans? Rhiannon Garth Jones took a closer look here.

Mineral weathering, methane capture, and more

Mineral weathering is another contender in the CO2 removal mix. One technology that recently received $2.4m in funding is Seattle-based Lithos’ enhanced weathering process – a mineral weathering process that could capture CO2 at a gigatonne scale. According to Frontier, Lithos spreads basalt on croplands to increase dissolved organic carbon, before eventually being stored as ocean bicarbonate. The idea is to maximise CO2 removal while bolstering crop growth.

Closer to home, SAC Consulting in Edinburgh will receive £2.9m to capture the methane produced by cattle and cut emissions from the livestock farming sector; Synthetic Biology in San Francisco has received an R&D grant to synthesise a polymer within algae that is capable of sequestering atmospheric CO2 at a large scale; and Charm Industrial is converting plants into a carbon-rich liquid that is pumped underground.

To do the latter, Charm grows cellulosic biomass that captures CO2 from the atmosphere. It is then harvested, ground, and heated, before being turned into a bio-oil that is pumped underground.

Even the concrete beneath our feet could be used as a carbon sink. CarbonCure is injecting CO2 into its concrete mixes, which it says is not only comparable in cost to traditional concrete, but stronger.

And then, we have solar engineering – arguably the first technology that comes into many of our minds when we think of carbon removal. All sorts of geoengineering technologies exist in this sphere including cirrus cloud thinning, stratospheric aerosol scattering, and marine cloud brightening.

Ethical issues?

Interestingly, Harvard’s Solar Geoengineering Research Programme referred to geoengineering as ‘a set of emerging technologies that could manipulate the environment and partially offset some of the impacts of climate change’.

Therein lies the problem for many. What are the consequences of ‘manipulating the environment’, especially if these technologies fall into unscrupulous hands?

In her excellent blog for SCI on geoengineering, Rhiannon Garth-Jones referred to the Haida Corporation Salmon trial. In this trial, 120 tonnes of iron compound were deposited in the migration routes of pink and sockeye salmon in the Pacific Ocean, which resulted in a several-month-long phytoplankton bloom.

It was seen by many as a success. The phytoplankton fed fish and increased biodiversity and the iron sequestered carbon; but Environment Canada believed the corporation violated national environmental laws by depositing iron without a permit.

History teaches us that profit vs. planet tussles don’t always go the way we would like, and the consequences of these technologies going into the wrong hands could be catastrophic.

On 29 June, The World Economic Forum called for a code of conduct for ocean-based CO2 removal; and the American Geophysical Union, a group of climate and planetary scientists, is leading the way in developing an ethical framework for climate intervention engagement.

We’re all feeling the effects of climate change. As I write this piece on 19 July, it is 39°C here in Greenford, London. 39°C in London! The earth is cracking, planes are circling (because the runways are melting), and grass fires are blazing in Croydon.

On days like today, it feels like we need all the innovation we can get.