I’m not convinced. planet-tracker says that refinement method, not ore source, determines carbon intensity. But deep sea nodules are richer than ore on land, which means they use less energy per unit of refined product. This is born out by the actual planet-tracker report: they themselves show that the highest estimates for sea-based carbon intensity are lower than all but the lowest estimates for land-based carbon intensity. Sea-based mining only looks bad if you compare the worst assumptions about sea-based mining with the best assumptions about land-based mining.

Planet-tracker also raises the concern that sea-based mining could theoretically disturb carbon which is sequestered on the ocean floor. However, there isn’t much circulation between the top of the ocean and the depth at which sea-based mining would occur, so this effect may be minimal or non-existent.

Additionally, the study neglects to consider how increased availability of critical metals could accelerate green technology adoption. Even if sea-based mining was somewhat worse for the environment on a kg co2/kg metal basis, it could be beneficial if it made EV batteries more economical.

I’m not saying that we should give companies unfettered access to the ocean floor. But planet-tracker’s call for a moratorium on deep sea mining is counterproductive.

The best course of action is to allow for a limited amount of mining in the Clarion Clipperton Zone so that scientists can study the resulting sediment plums. Advocates should be pushing the International Seabed Authority and governments to fund more research, not trying to block mining altogether.