Considerations for Using Polymetallic Nodules as Alternative Metal Extraction Resource: Focus on Energy-Related Applications

The worldwide imperative for transitioning to sustainable energy depends on the availability of essential minerals such as copper, lithium, nickel, cobalt, and rare earth elements. Some minerals and metals are especially susceptible to supply shortages and have been classified as “critical” due to the dangers connected with their availability and accessibility. Certain key metals possess diverse applications that extend beyond their utilization in clean technology. Polymetallic nodules (PMN) are being explored as a substitute source for essential materials like Co, Ni, Mn, Cu, etc., which are needed for the clean energy transition in the electrical mobility sector. These minerals are mostly used for energy storage purposes rather than energy generation. Unlike land-based resources that are processed individually to recover each metal, PMN contains multiple essential metals that can be simultaneously retrieved. Extracting battery metals from seabed resources would mitigate supply vulnerabilities associated with terrestrial resources. While there is currently no evidence of terrestrial resource depletion, recent initiatives in Australia involving alternative ore exploitation and the use of nickel pig iron from laterite ores in China and Indonesia for battery-grade nickel sulfate production indicate a growing interest in utilizing terrestrial resources. This chapter compares the energy needed to create battery metal precursors and metal from polymetallic sea nodules with the energy required to produce these precursors from land-based resources as part of the cathode mix. These values exhibit a favorable comparison. This comparison enables the allocation of energy costs in MJ/km for the energy consumed during battery production. Consequently, the emissions associated with the assigned energy during a life cycle study of a vehicle utilizing a particular battery capacity can be approximated as grams of carbon dioxide per kilometer (gm CO2/km). The superiority of polymetallic nodules is increased when energy allocation is specifically directed toward the production of saleable manganese product. India has recently been researching the utilization of PMN resources in the energy storage sector. This research has focused on developing flow sheets, determining the energy requirements for production, and assessing GHG emissions. The gross energy needs (GER) for hydrometallurgical operations, ranging from 9000 to 15,600 MJ/T, and pyrometallurgical processes utilizing CNG, which is 10,000 MJ/T, while recovering manganese bearing products, are translated to energy requirements for battery use in MJ/km and emissions. Utilizing renewable energy sources in the established processes might further decrease the emissions generated during the process. While it seems promising to utilize sea bed nodule resources for battery precursor production with reasonable energy use and emissions per kilometer for specific cases, further research is required to actualize this potential. This entails recalculating the net present value of products obtained from sea nodule processing based on additional experiments.