Can ocean-based CO₂ removal deliver on our climate goals?

The ocean has enormous – and largely untapped – potential to cycle and sequester excess atmospheric carbon through processes like seaweed cultivation. So how can stakeholders tap into this potential to scale CO₂ removal efforts and deliver climate wins?

Ocean conservation is closely linked to the fight against climate change

“At the end of the day, carbon dioxide removal is ocean conservation,” Brad Ack, chief innovation officer of Ocean Visions told delegates at the recent World Ocean Summit. Ack, who transitioned to ocean biodiversity conservation mid-career, explained that though we’re in a global race to preserve marine ecosystems, we’ve been outpaced by the larger changes in the climate.

Surplus carbon dioxide is heavily concentrated in the upper layer of the ocean. This additional CO₂ contributes to excess heat that is driving marine heatwaves, changes in ocean currents, species migration and ocean acidification. Ack told delegates that the body of heat is roughly equivalent to five atomic bombs worth of heat going into the ocean every second.

How can the ocean remove atmospheric carbon?

Ack explained that the ocean stores 50 times more carbon in bicarbonate and carbonate forms – like shellfish, seagrasses and seaweeds – in the bottom of the sea than what’s in the atmosphere today. This means that with minor tweaks that lead to increases in overall carbon storage, the ocean can make a huge dent in our collective carbon removal efforts.

Broadly speaking, the ocean cycles carbon in two patterns. One is chemical – where ocean water interacts with alkaline material to make it less acidic. Over millennia, these geologic processes allow the ocean to store carbon in safe forms in the benthic zone.

What does ocean CO₂ removal look like?

“[Think about it as an] antacid for an ocean that is in severe distress,” Ack responded when asked about specific de-carbonising methods. “We’ve put all this acid into the ocean – that’s what CO₂ is, it makes the ocean more acidic – we’ve got a very upset ocean, [so an] antacid could possibly help to reverse that acidification problem.”

Bivalve production may help de-acidify and remediate ocean waters© Offshore Shellfish

Though this might conjure images of ships dumping quicklime into the sea, Ack assured the audience that this wasn’t what he had in mind. His startup, Ocean Visions, is working on “roadmaps” that outline key technologies and strategies to de-acidify and de-carbonise the ocean. When it comes to enhancing ocean alkalinity, seaweed cultivation is emerging as a viable strategy – but Ack stressed that more research and development (R&D) was needed before he could give macroalgae production a full-throated endorsement.

What can marine stakeholders do now?

Ack believes that rapidly scaling the R&D effort is a necessary first step. Ocean Visions is currently accepting proposals for science on ocean alkalinity enhancement – a $10 million funding opportunity that hopes to identify approaches that safely, permanently and cost-effectively sequester atmospheric carbon at scale. Ack stressed that Ocean Visions isn’t advocating for any specific decarbonisation strategy at present. “We don’t know enough yet to deploy them,” he explained, but he wants to get the best minds together to make progress on the issue.

Ack also acknowledged that the existing governance structure for international waters might need to be re-assessed if ocean CO₂ removal gains traction. Contributions from maritime industries like aquaculture will be essential for testing and verifying de-carbonisation strategies. The existing laws that govern what individuals can do in international waters – the London Convention – might need expanded language around research to make inroads in this area.

Megan Howell, The Fish Site, 13 April 2022. Full article.

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