Development and Subsea Testing of Polymetallic Nodule Crusher for Underwater Mining Machine

Polymetallic nodules found in the deep oceans are viewed as potential resources for meeting the world's demand of many metals in the near future. Polymetallic nodule mining systems require subsea crushing systems for reducing the size of nodules to facilitate energy-efficient and safe pumping through risers of optimum size. Polymetallic nodules are friable, and deep-sea crushing has to be done with care to minimize the formation of fines, while obtaining the required size reduction. The crusher could also encounter objects with greater hardness during operation like small rocks, splinters, long fish bones, and shark teeth. All components in the crusher should be capable of operating in the deep ocean environment, which is hyperbaric and sediment laden. The equipment should be compact with minimum weight. Reversal of direction and dumping arrangements in the event of stalling are other essential design requirements. An underwater crusher capable of crushing mined nodules from a maximum size of 100 mm to a crushed size of 30 mm was developed using principles of design synthesis. The crusher was tested in land and integrated into a remotely operated crawler-based underwater mining machine that could mine and pump nodules through a flexible riser. The system was tested using artificial nodules at 512-m water depth off the Malvan coast in the Arabian Sea. This paper describes developmental methodology, land-based performance tests, and sea trials conducted on the developed crusher.

Polymetallic Nodules: Resource Potential and Mining Prospects

Deep-sea minerals such as polymetallic nodules have attracted significant interest among stakeholders not only for evaluating their potential as an alternative source of critical metals that are required for various industrial applications including green energy but also in developing technology for their exploitation. There has been a steady increase in the number of contractors having exploration rights over large tracts on the seafloor in the “Area,” and the International Seabed Authority that is mandated with the responsibility of regulating such activities is in the process of preparing a code for exploitation of these deep-sea minerals. This commentary takes a look at the resource potential and mining prospects of polymetallic nodules while addressing the economic and environmental issues associated with them.

Habitat Mapping for Ecosystem-Based Management of Deep-Sea Mining

Spatial considerations are important at multiple stages in the development of a deep-sea mining (DSM) project, from resource definition, to identification of preservation and management zones within a contract area, to planning of suitable ecological strata for baseline studies and impact assessment, to mine planning and adaptive management. Large investments are made to collect remote sensing data early in exploration to support geological resource studies, but environmental considerations are often instigated at later stages of exploration and can become disconnected from spatial frameworks. We outline a process of harmonizing the environmental and geological aspects of DSM project development by incorporating a habitat approach early in the development cycle. This habitat approach supports ecosystem-based management, which is a central requirement of environmental assessments. Geostatistical techniques are described that are used alongside a hierarchical classification scheme to describe and map geoforms and substrates. This foundational habitat model can form the basis of spatially explicit ecosystem models and can inform sampling design and spatial planning at critical junctures of a project development, ensuring that sampling campaigns are connected by an ecosystem logic early in the cycle. We provide an example application from the NORI-D polymetallic nodule exploration contract area in the Clarion-Clipperton Zone.

Long-Term Monitoring and Research in the Clarion-Clipperton Zone

The widely recognized need for large-scale transition from fossil to renewable energy sources has led to renewed effort to obtain metals needed for battery-based electric transportation and other functions. A potential source of some of these metals is the deposits of polymetallic nodules on the deep seafloor. If mining of these deposits proceeds in the coming decade, the enterprise creates an opportunity for extensive, long-term oceanographic research in the mining locations. The need to monitor environmental effects of mining activity can best be met with a near-continuous presence of a research platform in the vicinity. The platform could be a ship or potentially a semi-submersible platform like those used in the offshore oil industry. Such a facility might be supported by a consortium of mining companies and also provide opportunities for academic research in ocean and climate science.

Common Heritage of Mankind and the Deep Seabed Area Beyond National Jurisdiction: Past, Current, and Future Prospects

The common heritage of mankind (CHM) is of a relatively recent origin. This study examines Arvid Pardo's speech to the United Nations General Assembly in 1967, in which he urged that body to designate the seabed beyond national control as CHM. The commentary next looks at Part XI of the United Nations Convention on the Law of the Sea 82, as amended by the 1994 Agreement, which incorporates the CHM as a core principle governing mineral mining in the deep bottom area beyond national jurisdiction. Finally, it discusses CHM's future prospects in relation to the draft International Seabed Authority (ISA) Exploitation Regulations, the Enterprise, an ISA organ that has yet to be operationalized, and ongoing discussions about an international legally binding instrument on the conservation and sustainable use of marine biological diversity under the UNCLOS. The purpose of this study is to highlight the complexity surrounding the CHM, which is a key principle governing deep seabed activities.

Research on Novel Multi-Way Hydraulic Quick Connector for Underwater Production System

The underwater hydraulic connector is one of the most important components of an underwater oil production system. The equipment is mainly used to transport oil, chemical reagents, and other high-pressure fluids. We developed a novel underwater hydraulic multi-way quick connector system (MQCS) that is able to realize simultaneous, rapid, and precise plugging and unplugging of 10 underwater pipelines. It can be widely used for connection between subsea oil production equipment. The MQCS consists of a fixed plate assembly that is fixed to the oil production equipment and a free plate assembly that is connected to the pipelines on the drilling platform. This study describes the structure and working principle of the MQCS in detail. In addition, the process of the elastic collet clamping the mandrel was studied. Based on the finite element analysis software Abaqus, we investigated how the key geometric parameters of the elastic collet influence the axial force that needs to be provided by the underwater robot. A prototype was built based on the simulation results. To verify the performance of MQCS, a high-pressure chamber test was conducted. The results show that MQCS can accurately connect 10 high-pressure lines (about 69 MPa) in a high-pressure chamber and there is no pressure drop for 3 h after docking.

Navigating Environmental Approval Pathways for Deep Seabed Mining Projects in Areas Beyond National Jurisdiction (the Area)

Deep-seabed mining (DSM) is a developing industry with high potential to help meet the metal demand for the transition to a renewable energy world. No DSM projects have yet received environmental approval, although several are in progress, following the Environmental and Social Impact Assessment (ESIA) process that has been developed and widely applied for projects in national jurisdictions. Currently, the International Seabed Authority's (ISA) regulations, standards, and guidelines for mineral exploitation of seabed minerals in the Areas Beyond National Jurisdiction (the Area) are in draft form. Proponents are guided in their ESIA studies by the ISA's Recommendations for the Guidance of Contractors for the Assessment of the Possible Environmental Impacts Arising From Exploration for Marine Minerals in the Area and are proceeding in expectation that the currently draft regulations will be finalized by the time an environmental impact statement can be submitted. This paper discusses the pathways leading to environmental assessment and approvals, comparing the processes in national jurisdictions with those for projects in the Area.

Use of an Adaptive Management System to Minimize Impacts of Deep-Sea Nodule Collection

In the nascent deep-sea mining industry, there is currently a high degree of uncertainty about what impacts prolonged metal extraction will have on the receiving environment. There is also concern regarding the transparency and monitoring of operations since the target environment is extremely remote and inaccessible. Polymetallic nodule collection is being pursued, which is distinct from other forms of deep-sea mining in that the resource is distributed in a thin layer atop the seabed, unlike cobalt-rich crusts or massive sulfides, which are concentrated in specific areas. The second distribution of nodules provides opportunities for dynamic mine planning not available for other mineral sources as many constraints normally affecting mining operations like waste stripping or underground development are absent. Also, the highly mobile ship-based collection system that utilizes robotic collectors is easily relocated to other areas in response to emerging data on environmental constraints such as proximity to fragile habitats, sensitive species, or high cumulative impacts. An adaptive management system has been identified as a vital strategy to address scientific uncertainty of ecological impacts of deep-sea mining. The design features dynamic mine planning, scenario modeling, and impact forecasting. Also, operating data will be transparently viewable in a publicly available dashboard. This paper describes an implementation of a threshold-based framework for an effective adaptive management system designed to leverage the unique characteristics inherent to the resource.

Experimental Investigation Into Soil and Mechanical Pick-up Device Interaction in Nodule Mining of Deep Seabed

This research is focused to experimentally analyze the nodule picking efficiency of a deep sea mechanical pick-up device developed by National Institute of Ocean Technology, India. Experiments were conducted in a simulation tank with different operating parameters on a bentonite soil bed simulating the deep seabed and artificial nodules. Digging depth of the pick-up device, its angle and haulage velocity were the input variable parameters. From the experimental investigations, the values of the operating parameters that result in the highest pick-up efficiency were identified. The nodule picking efficiency increased as the pick-up device inclination was increased and reduced when the digging depth and haulage velocity were increased. The maximum nodule picking efficiency was 85% when the haulage speed, digging depth, and pick-up device inclination were 0.0375 m/s, 25 mm, and 30°, respectively. The research outcome would be useful in actual deep seabed conditions for efficient polymetallic nodule mining. Multiple mining machines with increased working width are proposed for large-scale operations.