A pioneering plan to use Britain’s seas to fight climate change has been scrapped because it was considered too expensive.
In letters seen by The Times, Planetary Technologies said it would not be going ahead with a large-scale plan to use Cornish waters to capture carbon from the atmosphere.
The Canadian company, which has received $1 million from a prize funded by Elon Musk, ran a pilot in Cornwall that started two years ago. It involved releasing hundreds of tonnes of magnesium hydroxide in its mineral form, brucite, near St Ives Bay. The mineral was released into the sea via an outlet owned by South West Water at Hayle.
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Magnesium hydroxide is better known as the compound milk of magnesia, a laxative, and the experiment had raised concerns among local conservationists who feared it might have unintended environmental consequences.
An independent study of the Cornish trial by the Plymouth Marine Laboratory found the approach held potential but it was so small that it did not achieve any large-scale carbon removal. Planetary Technologies has now ditched its plans for a larger project, blaming supply chains for magnesium hydroxide.
In letters sent to local groups on Thursday, Mike Kelland, the CEO of Planetary Technologies, wrote: “The scale-up of operations in Cornwall has been assessed as commercially unviable, and we will not be pursuing a wider programme in the region.”
The technique is known as ocean alkalinity enhancement, and uses an alkaline mineral to shift the pH value of the sea. More alkaline water speeds up the natural way oceans lock CO₂ away. Scientists and experts including the government’s advisers, the Climate Change Committee, say removing CO₂ from the atmosphere will be vital to stave off dangerous global warming.
The company appears to have paused its interest in any UK carbon-removal schemes. “We are not currently conducting any other trials in the UK,” Kelland wrote.
Local opponents were delighted by the scheme being axed but questioned the reason the company gave for its decision.
“I’m relieved that Planetary Technologies have left Cornwall but I don’t buy their explanation. I think the fact that the community and the Environment Agency held them to account has made them scarper,” said Senara Wilson-Hodges, a local campaigner, referring to the environmental regulator for England.
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She added: “The design of the experiment was sloppy, the fact that our bay was monetised by Planetary selling carbon credits to Shopify [a commerce platform] was unethical, and their understanding of our marine ecosystem and the community living in this area was cavalier. It’s the fact that we discovered all of this that has made Planetary leave town.”
Wilson-Hodges, a councillor in St Ives, said she saw the experiment as a “huge distraction” from the task of reducing carbon emissions.
The UN’s climate science panel, the Intergovernmental Panel on Climate Change, has said CO₂ removals will be vital if the world is to meet its target of holding global warming to 1.5C, but has not prescribed which approaches would be best. Other ideas are being tested in the UK, including a tower built by a French energy firm capturing CO₂ from the air at the port of Lowestoft, Suffolk.
A Planetary Technologies spokesperson said: “Specifically, we were unable to identify a local, cost-effective source of alkalinity — a critical requirement for responsible long-term deployment. This decision reflects logistical realities rather than a reflection on the trial’s environmental or technical outcomes.
“Further, we conducted an extensive review of potential UK-based sources but were unable to identify a partner that could meet our criteria for purity, traceability and sustainability at scale.”
