I conducted reasearch on the proposed enterprise in the 1980s. A goal, and the primary one evident in the literature, was manganese nodule mining. Producing manganese.
I don't have my original references handy, but some citations:
The market price of Mn ore is about $0.01/lb of contained Mn.
A good Mn nodule might contain 1% cobalt. It would be really stupid to mine these things for their manganese. Of course you'd sell what Mn you could, but that's not the value proposition here.
I don't have my original references handy, but some citations:
https://epubs.siam.org/doi/abs/10.1137/0143008
https://www.sciencedirect.com/science/article/pii/0160932778...
https://link.springer.com/article/10.1007/BF03354283