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Science & Innovation

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.

Science & Innovation

Many believe that greenhouse gas removal technologies will be necessary if we’re to reach net zero by 2050. In the first of our two-part geoengineering feature, we look at some of the difference-makers.

This week, a friend of mine played a tennis match just north of London. The game was due to take place at 18:00 but was deferred for an hour because it was 39°C. This came a day after Rishi Sunak, who may become the UK’s next Prime Minister, warned about going ‘too hard and too fast’ on net zero measures.

It’s looking increasingly likely that the implementation of environmental policies isn’t happening quickly enough; so, if we want to avoid catastrophic climate change, we will need to develop technologies that pull carbon dioxide from the atmosphere.

Thermometer reading 40C

Mercury rising: the UK recorded record high temperatures this week.

Certainly, that’s the UK government’s perspective. ‘Greenhouse Gas Removal technology will be essential to meeting the UK’s climate change target of net zero carbon emissions by 2050,’ it said. ‘These technologies will be necessary to offset emissions from hard to decarbonise areas, such as parts of the agriculture and aviation sectors.’

Thankfully, work is underway to make this happen. And it is more than just the pang of the environmental conscience that has stirred the private sector into action. There is much money to be made from geoengineering. Indeed, a CNBC story has estimated that it could be a trillion dollar market by 2050.

The public investment has been relatively modest by some. The UK government recently pledged £54m in funding towards 15 different carbon removal technologies. But some in the private sector have dollar signs in their eyes.

A collaborative called Frontier – funded by Stripe, Alphabet, Shopify, Meta, McKinsey, and tens of thousands of businesses using Stripe Climate – has made an advance market commitment to spend an initial $925m on permanent carbon removal technologies between 2022 and 2030.

‘Models project that by 2050 we will need to permanently remove billions of tons of CO2 from the atmosphere every year,’ it states. ‘To date, fewer than 10,000 tons have been removed in total.’ The capital it has committed is designed to help companies developing carbon removal solutions to scale up.

The UK government has mentioned the need for a portfolio of carbon removal technologies to reach net zero. A cursory look reveals that there are many from which to choose, including direct air capture, the manipulation of the sea, advanced weathering, and solar engineering.

These methods are audacious, exciting, and controversial.

Direct air capture

The key, as ever, is to come up with low-carbon technologies that are both effective and economically viable. In that respect, direct air capture has emerged as a front runner. This technology often uses giant fans with filters, or chemical processes, to take CO2 from the air.

The difficulty is the amount of energy needed to power these processes and the source of this energy. The cost of removing each tonne of CO2 is also an impediment to growth – something that will need to fall for it to be implemented on a large scale.

Climeworks co-founders Jan Wurzbacher and Christoph Gebald at the Orca plant in Iceland.

Climeworks co-founders Jan Wurzbacher and Christoph Gebald at the Orca plant in Iceland. Image courtesy of Climeworks.

Nevertheless, significant strides have been made in recent times. Swiss company Climeworks raised US$650m in equity for its largest direct air capture plant, and last week it inked a 10-year deal with Microsoft to permanently remove 10,000 tonnes of CO2 emissions from the atmosphere on its behalf.

The company’s machines capture CO2 from ambient air by drawing air into the collector with a fan. The CO2 is captured on the surface through a selected filter material that sits inside the collectors. Once the filter is filled with CO2, the collector is closed, and the temperature is increased to 80–100°C, whereupon the CO2 is released.

And what becomes of the CO2 after that? The CO2 at its Orca facility (50km outside Reykjavík, Iceland) will be mixed with water and pumped deep underground. The carbon dioxide will then react with the basalt rock through natural mineralisation and turn into stone.

Climeworks CO2 turned into stone via Carbfix technology.

Climeworks CO2 turned into stone via Carbfix technology. Image courtesy of Climeworks.

And Climeworks isn’t the only one operating in this space. As part of the UK Government’s aforementioned £54m funding, London-based Mission Zero Technologies will receive £2.9 million to build a low-energy, heat-free way to pull CO2 from the air.

Sydney-based AspiraDAC has been backed by the Stripe Climate Fund to remove 500 tonnes of CO2 using its modular, solar-powered system. According to Frontier: ‘Its MOF (metal-organic framework) sorbent has low-temperature heat requirements and cheap material inputs, increasing the likelihood that AspiraDAC can help accelerate the production of lower-cost metal-organic frameworks which, historically, have been expensive and difficult to synthesise.’

The Stripe Climate Fund has also backed 8 Rivers Capital, LLC, and Origen Carbon Solutions, Inc to remove CO2 from the air using its direct air capture (DAC) technology. Frontier said: ‘The DAC technology accelerates the natural process of carbon mineralisation by contacting highly reactive slaked lime with ambient air to capture CO2. The resulting carbonate minerals are calcined to create a concentrated CO2 stream for geologic storage.’

Of course, direct air capture is just one of many CO2 removal solutions. In part two, next week, we’ll look at other promising technologies.