https://en.wikipedia.org/wiki/Iron_fertilization
This is illegal under the U.N. law of the Sea but thanks to Don Rumsfeld the U.S. is not a party to that law so if you only use ports in the U.S., Chile and a handful of other countries, nobody will stop you.
I wound up talking to some experts in the field and was told with no uncertainty not to try it, although I think the scientific arguments weren't entirely convincing.
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The gist of it is this. If you want to make people pay money to solve the global warming problems you run straight into
https://en.wikipedia.org/wiki/Collective_action_problem
if you build some system for shuffling money (e.g. "Carbon Credits") around you now have a new problem that people are going to steal it:
https://en.wikipedia.org/wiki/Enron
If you can create a fully economically competitive energy source or carbon removal system people will use it and our great-grandchildren will remember that we solved this problem.
If we screw around with other things, the "way out" is that the 8 billion population ends up under 2 billion. CO2 emissions will not be a problem then, but our great-grandchildren will assign a death count that is roughly Hitler plus Stalin squared to our current political order.
I don't know what political/economic system they'll end up with but the Roman experience would lead us to think that they'll reject everything our civilization believes in.
Maybe don't though.
- Phytoplankton blooms are often environmentally and economically harmful
- There's no actual guarantee you'll sequester carbon.
- Consider that the biomass may end up in an anaerobic environment and digested into methane. Now you've converted carbon dioxide into a greenhouse gas 23x more powerful.
- Iron may well not be the limiting factor in that part of the ocean & you'll just release carbon from your exhaust
- How much carbon did it take to create this iron?