They note that global demand by 2050 could reach about 60 million tonnes of copper for motors and grids, plus up to 10 million tonnes of nickel and 1.4 million tonnes of cobalt for batteries, implying more than a doubling of copper and nickel demand and a fivefold increase for cobalt relative to current levels. The team emphasizes that land-based mining of these metals already leads to extensive deforestation, generates 4 to 5 billion tonnes of waste rock and slag each year, and in the case of cobalt often relies on child labor according to UNICEF assessments.
The press release highlights deep sea polymetallic nodules in the Clarion-Clipperton Zone of the Pacific as an alternative resource because they contain manganese along with significant copper, nickel and cobalt.
A Max Planck team has demonstrated a smelting route in which dried deep sea ores are reduced with hydrogen in an electric arc furnace to extract these metals with much lower CO2 emissions than carbon-based processes. In the journal Science Advances they compare their hydrogen-based approach with the process used in the Nori-D project of Canadian company TMC, which relies on carbonaceous compounds for reduction.
According to the study, using hydrogen as the reductant can cut CO2 emissions from deep sea ore processing by more than 90 percent when combined with green hydrogen and renewable electricity. The researchers also calculate that their route uses nearly 20 percent less energy overall and requires fewer process steps than the carbon-based alternative. They stress, however, that deep sea mining itself still creates environmental pressures, so any deployment must be evaluated within a broader life cycle assessment.
Director Dierk Raabe states that he previously opposed deep sea mining to avoid repeating the impacts of terrestrial extraction but has reconsidered under strict environmental conditions. He argues that extraction of metals from deep sea nodules would avoid child labor and substantially reduce deforestation and waste compared to land deposits.
For one billion electric car batteries, University of Delaware researchers estimate that land deposits would generate around 63 billion tonnes of waste rock, whereas sourcing the same metals from deep sea ores would produce about 9 billion tonnes of rock waste.
Doctoral researcher Ubaid Manzoor explains that the group reduces dried deep sea ores directly in an electrically operated arc furnace using a hydrogen plasma. When the ore is melted and then cooled slightly before introducing hydrogen, the team can recover nearly all copper as pure metal, while hydrogen injection produces an alloy rich in copper, nickel and cobalt along with several manganese oxides, some of which are suitable as battery materials.
The composition of the alloy depends on the reduction time, and separating copper first simplifies subsequent processing of the remaining alloy. Manzoor notes that the group has already published a related process for extracting nickel from land-based ores with lower climate impact.
The researchers see their work as one component in a comprehensive assessment of whether and how deep sea mining should proceed. They provide process and emissions data intended to inform international negotiations that compare the environmental impacts of deep sea versus land-based mining and processing. Manzoor says the goal is to supply a sustainable extraction method and robust data for such decisions, while Raabe concludes that moving away from a CO2-intensive economy will require accepting some difficult trade-offs.
Research Report:Low-waste, single-step, sustainable extraction of critical metals from deep-sea polymetallic nodules
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