Ocean geo-engineering

Naturally, the ppl who brought you fossil fuels and the climate emergency, are in favour of geo-engineering, which will take the carbon dioxide they've put into the atmosphere out again.  Presumably, taxpayers will pay for geo-engineering while oil and coal companies pocket the profits made from fossil fuels.  The trouble is, geo-engineering risks being some airy-fairy pious notion which is really about fossil fuel companies trying to postpone zero- carbon.  The unproven geo-engineering techniques put forward may persuade some that the need to slash emissions is reduced, thus in fact slowing our transition to zero carbon.

In reality, though, we will surely need it, because the world is very unlikely to cut emissions enough to avoid a 1.7 degree rise in global temperatures, and we still run a very serious risk of 2 degrees.   Negative emissions will help undo any 'overshoot' which happens.  The question of who will pay for it remains.   You can depend on it: oil and coal companies and those who made money from pumping CO2 into the atmosphere will not be putting up their hands.

From The Guardian:

Tom Green has a plan to tackle climate change. The British biologist and director of the charity Project Vesta wants to turn a trillion tonnes of CO2 into rock, and sink it to the bottom of the sea.

Green admits the idea is “audacious”. It would involve locking away atmospheric carbon by dropping pea-coloured sand into the ocean. The sand is made of ground olivine – an abundant volcanic rock, known to jewellers as peridot – and, if Green’s calculations are correct, depositing it offshore on 2% of the world’s coastlines would capture 100% of total global annual carbon emissions.

The plan relies on a natural process called weathering. “Weathering has been working on the planet for billions of years,” says Green, a graduate of Harvard Business School who runs Project Vesta from San Francisco. “When rain falls on volcanic rocks, they dissolve a little in the water, causing a chemical reaction that uses carbon dioxide from the atmosphere. The carbon ends up in the ocean, where it’s used by marine-calcifying organisms like corals and shell-making animals, whose skeletons and shells sink to the bottom of the ocean as sediment and eventually become limestone.”

Olivine weathers easily, and allowing ocean currents to churn it up, says Green, “will make it dissolve much more quickly, to happen on a human-relevant timescale”. It is not a rare mineral: there are beaches in the Galápagos Islands and in Hawaii that are green with olivine-rich sand.

The idea of using the sea to absorb excess carbon is not far-fetched, says Green. Ocean water can hold 150 times more CO2 than air, per unit of volume. “The ocean has already taken up about 30% of the excess carbon dioxide that we’ve emitted as a society,” he says. He and his colleagues are gearing up to test their process in two similar Caribbean coves, one acting as an untouched “control” in the experiment.

There remain many unknowns. Would such an intervention work? Who gets to decide if it should go ahead? Could there be side-effects? It is complex chemistry, and the natural process of weathering would be accelerated to an unnatural pace. Our understanding of the workings of the ocean is a mere drop in the proverbial. But with our race to mend the planet having taken on Sisyphean overtones, there is still hope that the vast, churning seas can be our lifeline.

Increasing carbon capture naturally on land – by planting trees, for example – will not remove enough CO2 to halt global heating. Peter Wadhams, head of the Polar Ocean Physics Group at Cambridge University and author of A Farewell to Ice, says: “If you want to get rid of the industrial emissions from Europe, you’d have to turn Europe into one big primeval forest. It works, but it’s not good enough alone.”

There are many ingenious ideas being discussed. Coastlines could be rewilded with underwater forests of kelp or seagrass, surface water cooled by generating air bubbles to whoosh cold water up from the deep, and marine clouds sprayed with seawater to reflect more heat from the sun.

As the UK prepares to host the UN Climate Change Conference (Cop26) in November, dozens of these projects are being trialled. Most rely on the ocean’s many natural balance-restoring processes: enhancing them to help slow cooling, to lock away carbon, to protect Arctic ice or even to reduce the threat of hurricanes.

Gaurav Sant, director of the UCLA Institute for Carbon Management, [talks about]  another concept, which he is helping to develop just a few hundred miles down the coast from Green, where UCLA engineers have developed a machine that mimics how seashells form. Called a flow reactor, the machine sucks seawater in, and an electrical charge makes it alkaline, which triggers the CO2 to react with the seawater’s magnesium and calcium, producing limestone and magnesite (like forming shells). The water then flows out and, depleted of its captured CO2, is ready to take up more. A byproduct of this process – hydrogen – can be extracted for fuel.

It’s a similar concept to weathering olivine in the ocean, and Sant’s plan is for initial small studies before a gradual scaling up. The team aims to remove between 10 and 20 gigatonnes of CO2 from the atmosphere, starting in 2050.

Sant says it will be a huge challenge to build a system large enough – and then to build thousands more. “Anyone saying ‘we’re going to do this in five years’, is greatly underestimating the challenge,” he says. “We’re talking about an enormous enterprise, the size and scale of which humanity has not seen before.”

Volcanic olivine, which Project Vesta is trialling as a way to capture carbon absorbed in oceans.