Green Manganese Pulls Four Metals From Nodules in One Step

Green Manganese said initial bench-scale testing of its hydrometallurgical platform recovered more than 90% of the manganese, nickel, cobalt and copper contained in polymetallic nodules in a single process.

Green Manganese says it has recovered more than 90% of the manganese, nickel, cobalt and copper contained in polymetallic nodules using a single hydrometallurgical process, a result the company reported from initial bench-scale testing. The claim, if it survives the journey from laboratory glassware to a continuous plant, addresses the least glamorous and most stubborn problem in the seabed minerals debate: not how to lift the rocks, but what to do with them once they are on deck.

Why a one-step route matters for nodules

Polymetallic nodules are potato-sized concretions that sit on the deep ocean floor and contain a mix of four metals that the energy transition consumes in bulk. That mixed chemistry is both their attraction and their problem. Conventional processing flowsheets tend to treat nodules as a sequence of separate problems: a high-temperature step to deal with the manganese-rich matrix, then downstream circuits to pull out the nickel, cobalt and copper, each with its own reagents, residues and capital cost. Every additional unit operation adds equipment, energy, working capital and another place for metal to be lost.

A hydrometallurgical platform — hydrometallurgy meaning leaching metals into solution with acids or other chemistry rather than smelting them at high temperature — collapses some of that. Doing it in a single process, as Green Manganese describes it, means one leach handling all four payable metals at once. The company's stated recovery of over 90% across manganese, nickel, cobalt and copper is the headline number because recovery is what determines how much of the orebody actually turns into revenue. A flowsheet that leaves a fifth of the manganese in the residue is a very different business from one that does not.

The result was reported by Mining.com. It is a company disclosure, and it describes initial bench-scale work — the earliest tier of metallurgical testing, typically conducted in batches measured in grams or litres.

What bench scale does and does not prove

Bench-scale testwork is a necessary first gate, not a verdict. It establishes that the chemistry works on a given sample under controlled conditions. What it does not establish is how that chemistry behaves when it runs continuously for weeks, when feed grade varies, when impurities accumulate in the recycled liquor, when reagents have to be regenerated rather than simply added fresh from a bottle, and when the residue has to be dewatered and disposed of at industrial volume.

The usual progression from here is piloting at continuously operating scale, then a demonstration plant, each stage consuming capital and time. Metallurgical recoveries commonly slip between bench and pilot, and the economics of a nodule flowsheet are unusually sensitive to that slippage because manganese is by far the largest component by mass but the cheapest per tonne. Manganese units have to be recovered efficiently and sold into a real market for the flowsheet to pay its way; nickel, cobalt and copper carry the value density but arrive in far smaller quantities.

Investors evaluating claims of this type should watch for three specific follow-ups: whether the recoveries hold on a locked-cycle or continuous test rather than a single batch, what reagent consumption per tonne looks like, and what the process does with the residue. Those three numbers, more than the recovery headline, decide whether a route is commercially viable.

Processing is where the seabed story has repeatedly stalled

The deep-sea minerals sector has spent the better part of a decade arguing about collection systems, environmental baselines and international permitting, and comparatively little time convincing metallurgists that the material can be turned into saleable product at a competitive cost. Onshore nickel laterite and manganese ore already have established, depreciated processing capacity. Any nodule route has to beat that incumbency, not merely function.

That is the structural context for Green Manganese's announcement. A simplified flowsheet is the kind of claim that, if validated at scale, changes the capital intensity of the whole proposition — and capital intensity is the variable that has kept seabed nickel and manganese out of the supply picture despite years of resource definition work.

Permitting sits alongside it as the second unresolved gate. Commercial-scale collection in international waters remains governed by a regulatory framework that is still being negotiated, and national-waters projects face their own approval processes and environmental litigation risk. A processing breakthrough does not move those timelines. It does, however, change what happens if and when they do move: a developer with a proven, low-complexity flowsheet is in a materially better position to attract project finance than one still choosing between competing routes.

The demand backdrop the flowsheet is aimed at

All four metals in the nodule basket sit on critical minerals lists in the United States and Europe, and all four are exposed to concentrated refining capacity outside those jurisdictions. Manganese in particular is under-discussed relative to its role: it is a bulk input to steel and an increasingly important one to lithium-ion cathode chemistries that lean on manganese to reduce nickel and cobalt loadings. High-purity manganese sulphate capacity, specifically, is thin outside a small number of producers.

That is the demand case a single-step nodule flowsheet is implicitly underwriting. Whether it gets tested depends less on chemistry than on capital markets and regulators.

Market setting on the day

The news landed into a soft session for US equities. The S&P 500, tracked by SPY, closed at $757.39, down 0.46% on the day from a previous close of $760.88, with a day range of $756.15 to $760.35, as of 20:00 GMT on 15 September 2026. The Nasdaq 100 proxy QQQ finished at $704.54, off 0.65% from $709.18, and the Dow 30 proxy DIA closed at $521.23, down 0.62% from $524.49. Broad risk appetite was mildly negative rather than disorderly.

That matters for early-stage critical minerals developers in a practical way. Announcements of technical progress tend to be funded by equity raises rather than cash flow, and the receptiveness of the market to a pre-revenue processing story tracks the wider risk tone. A single soft session tells you little; a sustained one changes financing terms.

What to watch next

• Continuous or locked-cycle testwork. Do the 90%-plus recoveries hold outside a batch test, and on more than one nodule sample?
• Reagent and energy consumption. The operating cost case for hydrometallurgy lives or dies here.
• Residue handling. What is left over after four metals are leached out, and what does it cost to store or neutralise it?
• Product specification. Whether the manganese output meets battery-grade specification or only metallurgical-grade, which are very different markets.
• Feedstock access. A flowsheet needs nodules to process; supply agreements or resource access are the other half of the equation.

Until those questions have published answers, the appropriate weight to place on a bench-scale recovery figure is: promising, unproven, and one of several things that all have to go right.

Key facts

• Recovery reported: Over 90% for manganese, nickel, cobalt and copper
• Stage of testing: Initial bench-scale, single hydrometallurgical process
• Feedstock: Polymetallic (deep-sea) nodules
• S&P 500 (SPY) close: $757.39, -0.46%, as of 20:00 GMT 15 Sep 2026

Frequently asked questions

What did Green Manganese actually announce?

The company said initial bench-scale testing of its hydrometallurgical platform recovered more than 90% of the manganese, nickel, cobalt and copper contained in polymetallic nodules, and that it did so in a single process rather than through a sequence of separate recovery steps. The claim is attributed to the company and reflects early-stage laboratory work.

What is a polymetallic nodule?

Polymetallic nodules are small mineral concretions that form on the deep ocean floor over geological timescales. They contain a mix of manganese, nickel, cobalt and copper in a single piece of material. That mixed composition is why processing them is complex: conventional flowsheets typically need multiple stages to separate and recover each payable metal.

Why does single-process recovery matter?

Each additional processing stage adds equipment, energy, reagents, residue streams and capital cost, and each one is a place where metal can be lost. Combining recovery of all four metals into one hydrometallurgical step, if it holds at industrial scale, reduces capital intensity and simplifies the plant, which directly affects whether a nodule project can compete with established onshore supply.

Does bench-scale testing mean the process is commercially proven?

No. Bench-scale work is the earliest tier of metallurgical testing, usually conducted in small batches under controlled laboratory conditions. Commercial validation requires continuous piloting, then demonstration-scale operation, where recoveries can fall as feed varies, impurities build up in recycled solution, and reagents must be regenerated rather than added fresh.

What are the main hurdles to scaling this up?

Three stand out: proving the recoveries survive continuous rather than batch operation, establishing reagent and energy consumption per tonne to support an operating cost case, and demonstrating residue handling at industrial volume. Separately, commercial-scale nodule collection remains subject to unresolved international and national permitting frameworks that a processing advance does not change.

How did the wider market trade on the day of the announcement?

US equities closed modestly lower. The S&P 500 proxy SPY finished at $757.39, down 0.46%, the Nasdaq 100 proxy QQQ at $704.54, down 0.65%, and the Dow 30 proxy DIA at $521.23, down 0.62%, all as of 20:00 GMT on 15 September 2026. Risk tone was soft but not disorderly.

Sources

• Green Manganese demonstrates single process critical metals recovery from polymetallic nodules — Mining.com

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