Metso sold more stirred grinding mills in 2025 than in any previous year, supplying sites on several continents with more than twenty new Vertimill® units and other models that promise up to 35 percent lower power consumption than traditional ball mills. The record year reflects a sector-wide pivot toward energy-efficient comminution technologies that help miners curb operating costs and carbon emissions while boosting throughput.
Demand for the Finnish supplier’s mills surged as mine operators from copper and gold to iron-ore producers sought sharper control of energy use, which can account for 40 percent of a concentrator’s total power bill. According to Metso’s year-end statement, the 2025 installations added 67 MW of stirred-mill capacity globally, saving an estimated 36,550 kW of electricity and avoiding roughly 135,000 tonnes of carbon dioxide a year—equivalent to the annual footprint of about 20,200 Finns. Sales momentum put the company’s stirred-mill portfolio at the centre of capital projects and brownfield upgrades in regions where the technology had previously been rare.
Metso confirmed the milestone in a December update reported by industry outlet AZoMining, which noted the firm “saw record sales of stirred mills in 2025 as mining customers opted for energy-efficient grinding solutions” AZoMining.
The company’s stirred-mill range—Vertimill®, HIGmill™, Stirred Media Detritor (SMD), and Vertical Power Mill (VPM) designs—uses either gravity-induced or fluidized mechanisms to intensify grinding while limiting energy draw. In new-build plants, the mills are frequently paired with high-pressure grinding rolls (HPGRs) upstream and Metso’s Concorde Cell™ flotation units downstream, creating a multi-stage flowsheet that lifts mineral recovery and reduces kilowatt-hours per tonne.
“Market conditions for stirred milling have evolved dramatically,” said Alan Boylston, Metso’s vice president for stirred mills. In the company’s update, Boylston noted that adoption is now spreading “beyond the traditional mining regions” and into “concentrators that previously had no stirred-mill applications.” Many existing plants are retrofitting secondary and tertiary circuits to take advantage of lower specific energy and modern digital controls.
The 2025 units reached diverse markets across sulphide copper operations in the Americas, gold mines in West Africa and Australasia, and iron-ore concentrators in Scandinavia and Brazil. The units operate at an average of 8,500 hours per year, underpinning the company’s global installed base of roughly 1,000 stirred mills accumulated over five decades of continuous development and supply.
Energy, Emissions, and Economics
Conventional tumbling mills rely on steel balls cascading in a rotating shell, a process that is both power-hungry and prone to generating excessive heat. Stirred mills, by contrast, use a vertical or horizontal chamber filled with small ceramic or steel media agitated by a centrally mounted screw or disc. Because the media are more uniformly distributed, they exert grinding force directly on ore particles, allowing the mill to run at slower tip speeds and lower horsepower per tonne.
Metso reports that across the 67 MW deployed in 2025, sites are reporting electricity reductions of “up to 35 percent,” translating into multi-million-euro savings on annual energy bills at current industrial tariff levels. For operators subject to carbon-pricing regimes, the avoided 135,000 tonnes of CO2 equate to an additional financial benefit. The figures use Finland’s per-capita emissions baseline of 6.7 tonnes; the implied savings mirror the yearly output of a mid-sized European town.
Technology Mix and Service Model
Beyond equipment supply, the stirred-mill range forms part of Metso Plus, a suite of products, services, and digital tools designed to improve environmental performance. Sensors embedded in the mills feed data to cloud platforms that predict liner wear, optimize media charge, and schedule maintenance windows. Metso supports the fleet through its global network of repair centres and on-site field service teams.
The product portfolio covers:
• Vertimill®—a gravity-induced mill widely used for secondary and tertiary grinding.
• HIGmill™—a fluidized-media design suited to fine and ultrafine grinding below 100 microns.
• SMD mills—compact units for regrind duties and lime slaking.
• VPM—a high-capacity vertical stirred mill for bulk tonnage applications.
Each platform can be specified with ceramic or steel media and integrated into bespoke circuits that include HPGRs, ball mills, or flash flotation, depending on ore characteristics. Metso contends that the modular approach enables miners to phase in energy-efficient equipment without a full concentrator rebuild.
Drivers Behind the Spending Wave
Several factors converged in 2025 to propel stirred-mill orders:
• Electricity costs remained volatile in many mining jurisdictions, incentivizing operators to cut power intensity.
• Large producers formalized net-zero roadmaps, tying executive remuneration to emissions targets.
• Ore grades continued to decline, requiring finer grind sizes to liberate metals—a duty for which stirred mills are well suited.
• Governments in Canada, Chile, and Australia tightened disclosure rules around Scope 1 and Scope 2 emissions, increasing reputational pressure on energy-hungry sites.
Boylston said miners now routinely run techno-economic models that assign a carbon price to every megawatt-hour, making the return on efficient comminution “straightforward to justify to boards and investors.” First-time adopters, he noted, are “often surprised by the operational flexibility” of stirred mills, citing rapid media change-outs and low liner consumption.
Placing Stirred Milling in the Wider Comminution Landscape
While stirred mills have carved out a dominant position in fine and ultrafine grinding, conventional SAG-ball circuits remain the workhorse for coarse primary crushing. Industry consultants say the sweet spot for Vertimill® units is typically below 150 microns, with HIGmill™ extending efficient grinding down to 10 microns. In hybrid flowsheets, a SAG or HPGR can provide the initial size reduction, feeding material to a stirred-mill tower for finishing before flotation or leaching.
Analysts at the Coalition for Eco-Efficient Comminution report that switching the final stage of grinding from a ball mill to a stirred mill can yield energy savings of 20–40 percent depending on ore hardness and target grind size. Although capital costs per installed kilowatt are higher, the total cost of ownership is often lower once power, media, and maintenance are factored in over the mill’s 20-year life.
Looking Ahead
Metso expects stirred-mill adoption to continue climbing in 2026 and beyond, driven by what it calls a “structural shift” toward ESG-aligned capital expenditure. The company is expanding manufacturing capacity in Finland and the United States and has hinted at new digital releases that link mill-sensor data to real-time flotation controls.
Industry strategists caution that no single technology can decarbonize comminution on its own; energy-efficient grinding must be paired with renewable power procurement, water-efficient flotation, and responsible tailings management. Still, Metso’s 2025 sales record underscores how quickly the mining supply chain can pivot when cost, carbon, and technology trends align.
The surge illustrates a maturing consensus that sustainability and productivity are not mutually exclusive. By demonstrating quantifiable cuts to kilowatt-hours and emissions across diverse commodities and geographies, stirred milling is moving from niche to mainstream, reshaping how new concentrators are designed and how legacy plants are upgraded.
Sources
- https://www.azomining.com/News.aspx?newsID=18554
