Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Development of new mining machine for cobalt-rich ferromanganese crustand achievement of excavation and dredging test on the deep seafloor
Kiyotaka Orita1, Seiya Kawano1, Shunsuke Nakamura1, Yoshiaki Igarashi1, Satoshi Shiokawa1, Saeko Nojiri1, Yoshiharu Ueyama1,Kazuo Watanabe2
1

Seafloor Mineral Resources Department, Japan Oil, Gas and Metals National Corporation, Minato, Tokyo, Japan
2Solution Service Department, Toyo Engineering Corporation, Narashino, Chiba, JapanABSTRACT

CHARACTERISTICS OF CRCS

For the commercial development of Cobalt-rich ferromanganese crusts,
the new mining technology is necessary because of their uniquemorphology and topography of the mining site. Therefore, a new cutter
head, which can automatically adjust the height of the cutter dependingon the relative change of the topography, was developed. Then, theexcavation and dredging test on the deep seafloor by using new cutter
head was conducted in July 2020. The test results showed that 649 kg of
the CRC ores was successfully collected as the first time in the world.

Table 1 shows the general distribution characteristics of CRCs andcomparison with other deep sea mineral resources (Manganese nodule(MN) and Seafloor Massive Sulfides (SMS)). CRCs distribute on theseamount slope and top of guyots with a very large area (>100 km2).
They cover the substrate i.e. Basalt and Limestone up to several cm thick.
Then, it is difficult to define the clear boundary between CRCs andsubstrates (Yamazaki, 1995).
Fig. 1 shows the uniaxial compressive strength (UCS) of CRCs andSubstrates, which were collected by using marine resources research
vessel the Hakurei. The average UCS of CRCs is less than 10 MPa. It isless than half of substrates.

KEY WORDS: Cobalt-rich ferromanganese crust, deep sea mining,
excavation test, mining machine, cutter head.

INTRODUCTION

CONCEPT OF THE NEW MINING METHODS FOR CRCS

Numerous amounts of Cobalt-rich ferromanganese Crusts (CRCs) werediscovered on the deep seafloor. They contain metals like Cobalt, Nickel
and platinum, which are necessary for producing batteries, in highconcentration. Thus, CRCs are expected as a new supply source of thesemetals.

Comparison of mining system with other deep sea mineral
resources
Appropriate method to propel on the mining site, to excavate CRCs andto collect excavated materials were selected by comparing with methods
for other deep sea mineral resources.

The Japanese government established the Basic Act on Ocean Policy in2007. Following the Act, the Cabinet approved the First Basic Plan on
Ocean Policy in 2008 and revise it in every 5 years to promote measuresrelated to the ocean. Then, the latest plan clearly mentioned that thegovernment should promote commercialization of development of deepsea mineral resources including CRCs (Cabinet Office, 2018). For thispurpose, The Ministry of Economy, Technology and Industry (METI)
and Japan Oil, Gas and Metals National Corporation (JOGMEC) decided
to conduct the excavation and dredging tests on the deep seafloor in 2020
to get fundamental information for designing mining system forcommercial use. (METI, 2018) Finally, they successfully conducted thetest on the deep seafloor. (JOGMEC, 2020)

Method of propulsion
Table 1 also shows the comparison of the propulsion methods of minerfor each deep sea mineral resources. The towed type miner andArchimedian-screw miner, which are suitable to move on the soft andflat sediments, were planned for collecting Manganese Nodules (MNs)
in 1970~80s. (Chung and Tsurusaki, 1994) On the other hand, the selfpropelled crawler type miner with was developed for excavating SMSs,
whose substrate is hard and rough, and successfully moved on the miningsite of SMSs (Okamoto et. al, 2019). The substrate of CRCs is not soft.
Moreover, the roughness of the mining site is larger than the one of MNs.
Thus, the self-propelled miner with crawler as well as SMSs was foundas appropriate.

In this paper, the project to develop new mining testing machine for
CRCs and the result of the excavation and dredging test on the deep
seafloor in the Takuyo No.5 seamount would be introduced.

1