The research, led by Valentina Pusateri of the Technical University of Denmark together with Mikołaj Owsianiak, Marja Rinne, Stig I. Olsen, Michael Z. Hauschild, and Sami Kara, tackles a stubborn blind spot in environmental accounting. Life cycle assessment, the standard tool for measuring the environmental footprint of products, has long struggled with how to treat metal resources. Recent methodological advances have shifted the focus from simple resource depletion toward resource dissipation: the idea that a metal becomes a genuine loss when it flows into a sink from which future users cannot realistically recover it. But existing methods typically treat all unrecovered metals as equally dissipated, ignoring the crucial fact that some stocks are far easier to tap than others, and that accessibility shifts as technologies mature and ore grades decline.

The Danish-Australian team proposed an elegantly simple criterion built on comparative profitability. A metal in a given anthropogenic stock is classified as dissipated when the net present value of extracting it from that stock is lower than the net present value of extracting the same metal from the reference stock, which the researchers defined as the upper continental crust, the most plentiful and dominant source of metals. In other words, if mining companies can always make more profit pulling copper out of the ground than out of a landfill, the landfilled copper is effectively inaccessible, no matter how concentrated it is. The authors were careful to stress that this does not mean the metal cannot physically be extracted; it means that in a global economy with a plentiful alternative source, the stock will not become the dominant supply, and its metal functions remain out of reach for the system as a whole.

To operationalize this dissipation quotient, the team assembled an unusually comprehensive economic dataset. They screened more than 500 publications and reports, ultimately extracting capital and operating expenditure data from 45 studies covering extraction of gold, copper, and iron from mine tailings, landfills, and hoarded stock such as end-of-life electronics. All costs were harmonized to 2024 euros using GDP deflators and exchange rates, and allocated per kilogram of extracted metal. Because revenues from metals are set on global exchange markets regardless of origin, the comparison reduces to a battle of costs: whichever source delivers metal more cheaply wins, and the loser is classified as dissipated.

The numbers reveal stark differences between the three metals. Extracting copper from anthropogenic stocks costs between roughly 6 and 670 euros per kilogram, while gold extraction runs between 28,000 and 44,000 euros per kilogram, a gap of about three orders of magnitude driven by the vastly different concentrations of the metals in waste streams. Iron sits at the bottom of the range, from about 0.07 to 120 euros per kilogram. Hoarded stock, meaning discarded phones, computers, and circuit boards, proved the most expensive source overall, despite its high metal concentrations, because collecting and dismantling small, complex devices is costly. Landfills showed the lowest average extraction costs for copper and iron, while tailings generally emerged as the most accessible stock type across the analysis.

The crucial twist comes from the reference side of the equation. Ore grades have fallen steadily since large-scale mining began, and the researchers projected this decline forward using an exponential decline model calibrated on historical data, cross-checked with a power regression approach. Copper ore grades have historically declined by about 1.72 percent per year, gold by about 1.05 percent, and iron by 0.61 percent. Because energy for mining and processing is the dominant cost driver and rises steeply as grades fall, the cost of primary extraction is expected to climb. At a 25-year horizon, the projected grade decline raises reference extraction costs by less than 10 percent. But by 300 years, the present value of costs is expected to increase by roughly 20 percent for gold, 200 percent for copper, and a striking 330 percent for iron relative to today.

Running the dissipation criterion across three time horizons of 25, 100, and 300 years produced a nuanced and somewhat counterintuitive picture. Accessibility generally increases with time, as primary mining becomes more expensive and the economic gap narrows. Gold consistently emerged as the most accessible metal, classified as non-dissipated in hoarded electronic waste, which aligns with the fact that gold recovery is already the main economic driver of e-waste recycling. Iron in tailings also performed relatively well. By contrast, hoarded iron, drawn from electronic waste where iron is merely a structural contaminant rather than a recovery target, was classified as dissipated across the entire range of uncertainty at every time horizon, with cost differences reaching minus 311 euros per kilogram at 300 years. Most other metal-stock combinations remained, on average, dissipated even at 300 years, though the uncertainty ranges were wide enough that many straddled the boundary.

The team then asked whether technological learning could flip these classifications. Using the classic Wright’s law framework, which links cost reduction to growth in cumulative output, they calculated the learning rates that emerging extraction technologies would need to break even with primary mining. For most combinations the required learning rates ranged from about 40 to 80 percent per doubling of output, far above the 15 to 25 percent considered realistic for emerging technologies, making a reclassification unlikely. Tailings were the notable exception. Copper recovery from tailings would need learning rates of only 25 to 40 percent, gold less than 20 percent, values well within reach as technologies mature. This finding dovetails with real-world developments, as copper is already being extracted from old mine tailings that were once written off as inaccessible.

The authors are candid about the limitations. Data availability was uneven, with no cost data at all for gold in landfills, and abandoned or dispersed technosphere stocks had to be excluded entirely. The assumption that anthropogenic metal concentrations stay constant over time may not hold if these stocks become active supply sources, and the assumption that metals recovered from waste fetch the same market price as virgin metal may fail where purity is lower. Yet sensitivity analysis suggested that the classifications are more sensitive to technology maturity and learning than to plausible shifts in reference ore grades. Recognizing this irreducible uncertainty, the researchers recommend a careful vocabulary shift: stocks meeting the criterion should be labeled potentially dissipative, and those clearing it potentially non-dissipative, rather than treated as certainties.

The implications reach well beyond academic methodology. Current footprinting approaches, including influential methods that assume everything not recycled within a given timeframe is dissipated, may systematically overestimate resource use impacts by ignoring the metal-, stock-, and time-specific nature of accessibility. The dissipation curves and breakthrough times generated by this framework could feed directly into next-generation life cycle impact assessment metrics, replacing crude recycling-rate proxies with economically grounded estimates of when, and whether, the metals we bury today will serve future generations. In a world where maximum technical circularity is estimated at only 30 to 40 percent and primary extraction will dominate for decades, knowing which of our discarded riches are truly lost, and which are merely waiting for the economics to turn, is a question whose answer is finally taking quantitative shape.

Subject of Research: Economic dissipation of copper, gold, and iron in anthropogenic stocks for resource footprinting

Article Title: Determining the dissipation of copper, gold, and iron resources in anthropogenic stocks based on extraction economics

Article References: Pusateri, V., Owsianiak, M., Rinne, M., Olsen, S. I., Hauschild, M. Z., & Kara, S. (2026). Determining the dissipation of copper, gold, and iron resources in anthropogenic stocks based on extraction economics. Journal of Industrial Ecology, 30(4), 1743-1759. https://doi.org/10.1007/s44498-026-00118-9

Image Credits: AI Generated

DOI: 10.1007/s44498-026-00118-9

Keywords: anthropogenic stocks, resource dissipation, life cycle assessment, circular economy, mine tailings, landfill mining, urban mining, ore grade decline, extraction economics, metal recycling, resource footprinting, technosphere

The stakes could hardly be higher. Primary platinum group metal production is geographically precarious, with South Africa’s Bushveld Igneous Complex supplying roughly 88.7 percent of the world’s platinum group metals and Russia’s palladium-rich Norilsk-Talnakh region alone accounting for about 43.8 percent of global palladium output. Life cycle assessments place the carbon footprint of producing a single kilogram of refined metal at between 28 and 42 tonnes of carbon dioxide equivalent, while the classic aqua regia leaching route releases toxic nitrogen oxide and chlorine-bearing gases. As millions of converters are scrapped each year, spent automotive catalyst has become the obvious secondary resource, but the industry has lacked a clean, low-energy route that works on the real, unprocessed solid material rather than pre-dissolved metal salts.

The Nottingham team, led by Christine Paul with Frankie Rawson, Katalin Kovács and Helena I. Gomes, turned to Cupriavidus metallidurans CH34, a bacterium with almost legendary resistance to toxic metals. Its defensive arsenal sits on two megaplasmids carrying metal-specific gene clusters including cop, czc and cnr, allowing it to shrug off millimolar concentrations of nickel, zinc, copper and cadmium. Crucially, the organism is also electrogenic: it forms biofilms on graphite electrodes and generates current densities of 15 to 150 milliamperes per square metre. Previous bioelectrochemical studies of precious metals had only ever worked with dissolved metal ions in model solutions, or with real catalyst material that had first been chemically leached. This new work, published in Cleaner Engineering and Technology, is the first to put an electroactive culture in direct contact with untreated spent catalyst solids.

The experimental design was elegantly simple. Dual-chamber H-type microbial fuel cells were built from borosilicate glass, with carbon felt electrodes separated by a perfluorinated sulfonic acid membrane and a ferricyanide catholyte chosen specifically so that the cathode would never limit the measured response. The anode chambers received untreated spent catalyst powder at loadings of 10,000, 50,000 and 100,000 parts per million, corresponding to pulp densities of 1, 5 and 10 percent, alongside catalyst-free controls. Eight reactor types, each run in biological triplicate, allowed the team to separate purely chemical effects from genuinely biological ones. After 168 hours of operation, inductively coupled plasma mass spectrometry tracked exactly where the platinum, palladium and rhodium had ended up across the liquid, biomass, electrode and residual solid fractions.

The first surprise came from the biomass data. At the lowest loading of 10,000 parts per million, the bacteria actually grew better than in the catalyst-free control, reaching 221.4 micrograms per millilitre of planktonic protein at 96 hours compared with 201.3 in the control, suggesting the moderate metal challenge stimulated rather than suppressed the culture. But at 50,000 and 100,000 parts per million, growth collapsed to just 60 to 75 percent below the control level. Scanning electron microscopy told part of the story: at the higher loadings, aggregated catalyst particles blanketed the carbon felt electrodes, masking the underlying fibre structure and leaving little visible biological material. The electrode-attached population fared better than the free-floating cells, but the overall picture was one of progressive physical and chemical suffocation.

That suffocation had two distinct sources. The first was acidity. Even in completely abiotic reactors, adding catalyst drove the anolyte pH down in a dose-dependent fashion, from 5.95 in the catalyst-free control to 4.87, 4.06 and 3.93 at the three loadings respectively. This chemical acid load occurred entirely without microbial help and, crucially, preceded the decline in bacterial growth, establishing that acidification was a cause rather than a consequence of the biological collapse. The second source was electrical. Open-circuit voltage peaked at an impressive 0.442 volts at 10,000 parts per million, actually exceeding the catalyst-free control, but fell to around 0.12 to 0.15 volts at higher loadings. Internal resistance told the same story, with activation resistance jumping from 142 ohms in the clean biotic reactor to 3688 ohms at low loading and over 7000 ohms at the highest concentrations, while power density plummeted by more than two orders of magnitude across the range.

Cyclic voltammetry added a further layer of insight. The anodic peak current at 10,000 parts per million reached 688.89 microamperes, more than double the 327.65 microamperes of the catalyst-free control, and the Randles-Ševčík slope, a measure of diffusion-coupled electron transfer, was likewise highest at moderate loading. But the weaker linearity of that fit hinted at extra processes beyond simple diffusion control, and at 50,000 and 100,000 parts per million the peak currents fell to 278.25 and 96.24 microamperes respectively, with increasingly non-Nernstian behaviour indicating quasi-reversible to irreversible electron transfer governed by kinetic limitations. In plain terms, the electrochemical conversation between bacteria and electrode was sharpest at moderate catalyst loading and progressively garbled as particles piled up on the surface.

The metal redistribution results were the most striking of all. Rhodium proved to be the star performer: at 10,000 parts per million, the biotic reactors mobilised 17.93 percent of the rhodium input, compared with just 0.87 percent of platinum and 1.20 percent of palladium. Moreover, 10.3 percent of the rhodium ended up associated with the bacterial biomass, a fraction that was below detection in the abiotic controls, pointing to a genuinely selective biological interaction. The explanation likely lies in catalyst chemistry: road-aged three-way catalysts contain rhodium predominantly in oxidised form, whereas platinum sits mostly as metal. Dissolving metallic platinum group metals requires both a high oxidation potential and a complexing ligand such as chloride, neither of which was present in the anolyte, but rhodium that is already oxidised can bypass that demanding first step. The biological contribution, however, was confined to biosorption and accumulation on the biomass rather than true dissolution of the solid matrix, and the authors are careful to note that no oxidation-state analysis confirmed reduction.

Perhaps the most counterintuitive finding was that mobilisation per gram of catalyst was highest at the lowest loading, despite the more favourable pH there. Platinum recovery per unit mass fell from 2.01 hundredths of a milligram per gram at 10,000 parts per million to 0.332 hundredths at 100,000 parts per million, with palladium and rhodium showing the same pattern. This points to accessible surface area, not acidity, as the true bottleneck: at high solids loadings, particles aggregate, the reactive surface shrinks, and the sheer mass of solid available for re-adsorption pulls dissolved species back out of solution. The same pulp-density penalty has been observed in conventional hydrometallurgical processing, where palladium and platinum recovery drops from above 90 percent at 5 to 8 percent solids to below 70 percent at 20 percent.

The honest conclusion is that this system, as it stands, cannot yet compete with industrial recovery: even at the optimum loading, less than 18 percent of rhodium and under 2 percent of platinum and palladium were mobilised. But the study does something arguably more valuable than demonstrating a working process. It maps the operational window, showing that the transition between sustained and suppressed performance lies somewhere between 10,000 and 50,000 parts per million, and it identifies the two mechanisms, chemical acidification and particulate fouling of the electrode, that constrain it. The authors sketch a roadmap of possible fixes: pH control to decouple acidification from surface effects, pre-washing the catalyst to reduce the acid load at source, fed-batch dosing to keep instantaneous loading within the functional window, or a two-stage configuration that separates mild chemical solubilisation from the bioelectrochemical step that the biology performs best, namely selectively capturing mobilised rhodium. Achieving process-relevant yields, they conclude, will require intervention at the solid-liquid interface rather than tinkering with the microbe itself. For a field desperate to break its dependence on South African ore bodies and 1200-degree furnaces, that is a map worth having.

Subject of Research: Bioelectrochemical recovery of platinum group metals from untreated spent automotive catalyst using Cupriavidus metallidurans

Article Title: Bioelectrochemical treatment of untreated spent car catalyst: Effects of solids loading on platinum group metal redistribution and process limitations

Article References: Paul, C., Rawson, F., Kovács, K., & Gomes, H. I. (2026). Bioelectrochemical treatment of untreated spent car catalyst: Effects of solids loading on platinum group metal redistribution and process limitations. Cleaner Engineering and Technology, 34, Article 101322. https://doi.org/10.1016/j.clet.2026.101322

Image Credits: AI Generated

DOI: 10.1016/j.clet.2026.101322

Keywords: platinum group metals, spent car catalyst, microbial fuel cell, Cupriavidus metallidurans, rhodium recovery, bioelectrochemical systems, urban mining, circular economy, biomining, hydrometallurgy, electroactive bacteria, metal recycling

The intellectual core of the review is the idea that electrochemistry offers a unified theoretical framework for manufacturing metallic systems. Unlike purely thermal or mechanical processes, electrochemical techniques manipulate matter at the level of ions and electrons, allowing engineers to control deposition, dissolution, and transformation with atomic-scale precision. Faraday’s laws established the quantitative relationship between electric charge and chemical change in the nineteenth century, but the past hundred years have seen that foundation expand into sophisticated models of electrode kinetics, mass transport, double-layer phenomena, and interfacial thermodynamics. The authors emphasize that this theoretical unification is what enabled the field to branch so successfully into electroplating, electrowinning, electroforming, electrochemical machining, and, more recently, additive electrochemical manufacturing.

Electroplating remains the most familiar face of the technology. What began as a decorative process for applying thin layers of silver, nickel, and chromium has evolved into a precision engineering discipline essential to corrosion protection, wear resistance, and electronic interconnection. Modern plating baths are formulated with additives that control grain size, crystallographic orientation, and internal stress, producing coatings whose properties can be tuned almost at will. The review highlights how the semiconductor industry’s dependence on electroplated copper interconnects, a breakthrough that sustained the continuation of Moore’s law in the early 2000s, exemplifies the way electrochemical manufacturing quietly underpins technologies that appear, on the surface, to have nothing to do with batteries or beakers.

Beyond coatings, the retrospective surveys electroforming and electrochemical machining as methods for producing complex metallic components that would be difficult or impossible to fabricate by casting or cutting. Electroforming builds parts atom by atom by depositing metal onto a mandrel, enabling the production of lightweight optical reflectors, precision meshes, and microstructured components with tolerances measured in micrometers. Electrochemical machining, by contrast, removes metal through controlled anodic dissolution, shaping superalloy turbine blades and medical implants without introducing the thermal stresses and microcracks associated with conventional machining. Because the tool never touches the workpiece, and because hardness is irrelevant to the process, electrochemical machining remains indispensable for the nickel-based superalloys and titanium alloys that define aerospace propulsion.

Perhaps the most consequential section of the review addresses primary metal extraction. Electrowinning and electrorefining have long been the backbone of copper, zinc, and aluminum production, and the authors trace how improvements in cell design, electrode materials, and electrolyte chemistry have steadily reduced energy consumption while improving product purity. The aluminum industry’s shift to inert anodes, still under intensive development, promises to eliminate the carbon dioxide emissions that currently accompany conventional Hall-Héroult smelting. Meanwhile, emerging electrochemical routes for iron and steel, including molten oxide electrolysis and hydrogen-assisted electroreduction, aim to replace the blast furnace, a technology responsible for roughly seven percent of global carbon dioxide emissions. The review frames these developments as the next great chapter in a hundred-year story of electrochemical scaling.

Recycling and urban mining form another frontier where electrochemistry is proving decisive. As the world accumulates end-of-life batteries, electronic waste, and mixed metal scrap, selective electrochemical recovery offers a low-temperature, low-emission alternative to pyrometallurgical smelting. Electrochemical methods can separate metals with high specificity by tuning electrode potentials, allowing cobalt, nickel, lithium, and copper to be reclaimed from complex feedstocks. The review notes that direct electrochemical relithiation of cathode materials, in which spent battery particles are rejuvenated in a molten salt or aqueous electrolyte, could dramatically shorten recycling loops and reduce the environmental burden of the clean energy transition itself. In this sense, electrochemical manufacturing is not only producing the metals of the future but also recovering them.

The retrospective also confronts persistent challenges that have limited electrochemical manufacturing’s reach. Energy efficiency remains a central concern, since many electrodeposition and extraction processes operate far from their thermodynamic minima due to overpotentials, ohmic losses, and side reactions such as hydrogen evolution. Scale-up is another hurdle: laboratory demonstrations of novel electrochemical synthesis often struggle to maintain uniform current distribution and product quality in industrial cells spanning many cubic meters. The authors call for deeper integration of electrochemical engineering with process modeling, machine learning, and in situ characterization, arguing that the field’s next century will depend on closing the gap between interfacial science and plant-scale practice. Standardization of electrolyte management, electrode durability, and life-cycle assessment will be equally critical.

Looking forward, the review identifies additive electrochemical manufacturing as a potentially disruptive convergence of old and new. Techniques that pattern metal deposition with light, scanning probes, or fluidic masks can now print complex three-dimensional structures at room temperature, bypassing the extreme heat and residual stress of laser-based metal printing. Combined with advances in flow cells, ionic liquids, and deep eutectic solvents that widen the window of depositable alloys, these methods point toward digital, electrified factories in which metal parts are grown rather than cast. The authors argue that such approaches align naturally with renewable electricity, since electrochemical processes can flexibly absorb intermittent power in a way that blast furnaces and foundries cannot.

The hundred-year retrospect ultimately delivers a message of continuity and urgency. The unified theories developed across the twentieth century have proven remarkably durable, providing the quantitative scaffolding on which every modern electrochemical manufacturing process rests. Yet the demands of the twenty-first century, decarbonized extraction, circular material flows, and atomically precise fabrication, will test that framework in unprecedented ways. What the review makes clear is that the tools for meeting those demands already exist in embryonic form, scattered across electroplating shops, smelters, battery recyclers, and semiconductor fabs. Consolidating them into a coherent manufacturing paradigm, the authors conclude, is the defining task of electrochemical engineering’s next hundred years.

Subject of Research: A critical retrospective of electrochemistry-enabled manufacturing advancements for metallic systems over the past 100 years

Article Title: Electrochemistry-enabled manufacturing advancements for metallic systems: a critical retrospect from unified theories to diverse applications over 100 years

Article References: Pan, S., Sundaram, M., Bruschi, S., Zheng, Y., Bertolini, R., Stevens, J., Zhao, B., Islam, T., & Ma, S. (2026). Electrochemistry-enabled manufacturing advancements for metallic systems: a critical retrospect from unified theories to diverse applications over 100 years. npj Advanced Manufacturing. https://doi.org/10.1038/s44334-026-00116-6

Image Credits: AI Generated

DOI: 10.1038/s44334-026-00116-6

Keywords: electrochemistry, manufacturing, metallic systems, electroplating, electrowinning, electrochemical machining, metal recycling, decarbonization, additive manufacturing, electrodeposition, Electrochemistry-enabled, advancements