You can’t use every approach as iron seeding and this both do the same thing and the oceans are finite.
So this isn’t a 1% solution, it’s not even a 0.1% soliton it might be a 0.01% solution. “50,000 tonnes of tephra – a bulk carrier vessel’s worth – offshore could sequester 2750 tonnes of atmospheric carbon dioxide. This, they said, equates to a cost of around £43 per tonne of carbon dioxide sequestered” assuming absolutely zero CO2 was released in the process.
Bulk carriers are quite efficient and could move 50,000 tons ~= 0.4 tons of CO2 per mile in a straight line. Which sounds fine except you can’t simply dump all 50,000 tons 1 mile off shore and expect anything useful to happen. If you can dump on average 50 tons per mile you just released ~400 tons to sequester 2750. And that’s assuming it somehow gets loaded and unloaded without releasing any extra CO2.