DSM projects. Section 5 reviews and evaluates an EU-sponsored Benefit-Cost Analysis of deep seabed mining (Cardno, 2016; Wakefield and Myers, 2018), and suggests an alternative way to structure the DSM evaluation. Section 6 discusses the key findings and offers a conclusion.

# **2. Deep Seabed Mining**

Seabed minerals are found in several kinds of formations. Polymetallic Sulfides (also known as “seafloor massive sulfides (SMS)”) occur on active and inactive hydrothermal vents located on mid-ocean ridges at tectonic plate boundaries in areas of active volcanism. Cobalt-rich crusts are found on the surfaces of sea mounts. Polymetallic nodules (also known as manganese nodules) are scattered on the surface of abyssal plains in deep ocean waters (World Bank 2017). Polymetallic nodules on seabeds in the Clarion–Clipperton Zone (CCZ) – a broad expanse in the Pacific Ocean between Hawaii and Baja California -- may contain more cobalt, magnesium, and nickel than the total known terrestrial deposits of these minerals (Hefferman, 2019).

The ISA has issued 18 exploratory contracts for polymetallic nodules (16 in the CCZ, and two in the Indian Ocean); seven for seafloor massive sulfides (SMS) in the South West Indian Ridge, Central Indian Ridge and the Mid-Atlantic Ridge; and five for cobalt-rich crusts in the Western Pacific Ocean (See Footnote 2). In 2011, Papua New Guinea issued the first (and so far, only) mining license to the Nautilus Mining company for the purpose of developing SMS deposits in an area 16 km off the coast of New Ireland. Known as the Solwara project, this lease contained 12 proposed sites, which were to be developed over a 20 year period. However, financing difficulties and local opposition aborted the Solwara project,<sup>7</sup> and the mining of polymetallic nodules in the CCZ zone is now seen as the most likely start of the DSM industry (Heffernan, 2019) (see footnote 4). There is still considerable interest in SMS mining, however (Dunn et al., 2018). The mining of cobalt crusts seems to be a more distant prospect.

DSM will involve several components. A production support vehicle (PSV) will be located on the ocean surface directly above the mine site, while mining equipment, adapted to the specific type of mineral deposit, will be used to excavate minerals from the seafloor. A riser/lift system will convey the extracted mixture of minerals, sediments, and water from the seabed to the PSV. At the PSV, a dewatering process will be used to remove minerals from the solution in which they are suspended. The dewatered minerals will then be loaded onto barges and shipped to onshore processing facilities, with the return water pumped back down the riser/lift system. The PSV will control the entire operation (World Bank 2017).

The different mineral formations are located at different depths, and the extraction periods and mining footprints will vary (World Bank, 2017). Seamounts with cobalt-rich crusts range in depth from 800 to 2,500 meters. Mining is expected to take place over a 20 year period. For the site located in the national waters of the Marshall Islands in the EU-sponsored benefit-cost analysis (Cardno 2016) – hereafter, “the EU BCA” -- this 20 year mining operation would leave a footprint of 470 km<sup>2</sup> .

> 7 See  “Collapse of PNG deep-sea mining venture sparks calls for moratorium”.

4