A French scientist says it would cost the Goro Nickel company in New Caledonia 50 million US dollars to set up a plant capable of filtering out manganese from its nickel production.
The manganese concentration in the planned mine's effluent is a key concern of environmentalists opposed to the two-billion US dollar project.
The scientist, Fabrice Colin of the IRD institute in Noumea, says the process to reduce manganese content from 100 milligrams a litre to 10 milligrams a litre is well understood and proven.
"It's perfectly understood by the operator. They can do that immediately. They are to invest 50 million dollars to have this process and it's an additional 50 million dollars per year to have it regulated."