France, Aug. 25 -- Deep-sea mining seeks to tap previously untouched seabed deposits of a range of commodities, including cobalt and nickel, but the fledgling industry has long been stalled by environmental concerns.

The government certificate issued this month is the next step in plans by Namibian Marine Phosphate (NMP) to dredge the ocean floor around 120 kilometres off the town of Walvis Bay for the key ingredient of fertilisers vital to agriculture.

NMP said the clearance does not mean it will immediately begin commercial mining operations as it still needs to complete permitting, including for the necessary land-based infrastructure.

But the certificate has raised alarm among conservationists, with the Confederation of Namibian Fi...