Single furnace turns low-grade iron ore into clean molten steel

Combining reduction and melting inside one continuous electric furnace cuts industrial carbon emissions in half while reducing domestic production costs by a quarter.

Nearly every modern structure, from skyscrapers and bridges to rail lines and vehicles, relies on steel, yet the underlying chemistry used to make the metal has scarcely changed since the nineteenth century.¹² Most of the world's virgin steel begins with solid iron ore heated alongside coal coke inside towering blast furnaces, stripping oxygen away at extreme temperatures before secondary facilities refine the liquid iron into usable grades.¹³ This traditional sequence generates roughly 7 percent of global carbon dioxide emissions, an output comparable to the entire fashion industry, while requiring multibillion-dollar industrial infrastructure designed to run uninterrupted for half a century.¹³

The challenge facing cleaner manufacturing is not a shortage of ideas, but the harsh economics of commodity metals. Steelmakers operate on slim profit margins, and existing mills cannot easily replace massive capital equipment without risking solvency.¹³ In the United States, domestic operators produce the majority of their finished steel by melting recycled scrap in electric arc furnaces, yet scrap cannot yield every critical grade on its own.³² Because impurities accumulate during recycling, American producers still rely on foreign suppliers for virgin pig iron, importing roughly 90 percent of the raw material required to blend into domestic scrap furnaces.³

How does conventional iron refining create so much pollution?

Conventional steelmaking generates enormous greenhouse gas volumes because it relies on solid carbon to strip oxygen atoms from iron oxide through multiple sequential heating stages.³² In standard blast furnaces, operators burn processed coal, known as coke, to generate heat and carbon monoxide gas.³¹ As the rising gas passes through descending chunks of solid ore, it binds with the oxygen in the ore, creating molten pig iron while releasing vast quantities of carbon dioxide into the atmosphere.¹³ That raw pig iron must then be transferred to a basic oxygen furnace, where additional oxygen is blown through the liquid to burn away excess carbon before the metal can be cast and shaped.³⁴

To make this multi-stage reaction run efficiently, conventional blast furnaces require premium, high-grade iron ore pellets and specialized coking plants, adding expensive pre-processing steps before melting even begins.³⁴ The requirement for solid-state reduction means low-grade ores containing less than 60 percent iron, fine powders, and industrial waste oxides are routinely discarded or left unmined.²⁴ Traditional mills must therefore maintain separate facilities for sintering, coking, reduction, and refining, multiplying both total energy demand and point-source emissions across the plant.³⁴

What changes when iron melts before reduction occurs?

Melting iron ore before stripping its oxygen allows chemical reduction to take place entirely in a liquid phase, collapsing several industrial steps into one continuous furnace. Laureen Meroueh, a mechanical engineer who earned her doctorate at the Massachusetts Institute of Technology, developed this single-step approach and founded the startup Hertha Metals in 2022 to commercialize it.¹³ The system uses an electric arc furnace powered by domestic natural gas and electricity to melt raw ore directly into refined molten steel, doing away with coal coke, sintering facilities, and separate basic oxygen furnaces.³

By conducting gaseous reduction inside the molten liquid rather than across solid rock surfaces, the furnace accepts raw ore of any grade or format, including sub-60 percent purity ores, loose fines, and millscale, which is the oxidized flake waste produced by conventional rolling mills.²³ Meroueh explained that performing reduction while iron oxide is molten removes the strict quality requirements that constrain legacy mills.³ The proprietary process melts the ore, strips the oxygen using injected gas, and adjusts the carbon content simultaneously in one vessel, producing finished liquid steel in a single continuous cycle.

This consolidation reduces overall operating energy use by 30 percent compared with conventional American steel mills, according to company reports.³² Operating with natural gas instead of coal coke cuts carbon dioxide emissions by at least 50 percent, while reducing the overall cost of making steel from iron ore by 25 percent compared with standard domestic methods.¹³ The furnace can also run on clean hydrogen without requiring hardware modifications, a fuel substitution that would eliminate up to 98 percent of carbon emissions once hydrogen supplies become commercially economical.²⁴

How is the continuous single-step furnace verified?

Hertha Metals verified the single-step chemistry by operating a continuous pilot facility in Conroe, Texas, just north of Houston, which has produced one metric ton of liquid steel per day since late 2024.² The company developed the pilot plant with approximately $20 million in venture funding raised from investors including Khosla Ventures, Breakthrough Energy Fellows, Pear VC, and Clean Energy Ventures.¹² The facility operates modular heat exchangers and steam turbines that capture hot off-gas leaving the furnace, regenerating electricity and recovering roughly 35 percent of the system's thermal energy on site.³

In addition to structural steel, the Conroe pilot plant demonstrated production of ultra-high-purity iron reaching 99.97 percent purity.²⁴ High-purity iron constitutes 70 percent of the total mass in permanent rare-earth neodymium magnets, which are essential components in electric vehicle motors, wind turbines, robotics, and defense hardware.² The United States currently imports more than 90 percent of this specialized iron, primarily from suppliers in China, leaving domestic advanced manufacturing vulnerable to foreign supply disruptions.²³

What are the limits of single-step smelting?

Pilot operations producing one metric ton per day demonstrate chemical viability, but they cannot prove commercial durability across hundreds of thousands of operating hours.¹⁴ Industrial steel manufacturing demands continuous, reliable output under severe thermal and mechanical stresses, and scaling pyrometallurgical hardware from single-ton batches to commercial volumes often introduces unforeseen engineering hurdles in refractories, gas flow dynamics, and slag management. Furthermore, the 50 percent emissions reduction relies on abundant fossil natural gas, meaning full decarbonization remains dependent on the future availability and price of green hydrogen.¹

The system's economic advantages also assume modular integration into existing steelmaking infrastructure rather than ground-up mill construction. Traditional steel mills represent decades of capital investment designed to operate for 50 years, making complete facility replacement unrealistic for most producers.³ Hertha Metals plans to integrate its ore-to-liquid furnace directly upstream of existing casting and rolling equipment, but widespread adoption requires established steelmakers to trust unproven reactor designs for their primary iron supply.

Scale remains the decisive hurdle in heavy industry. The company plans to break ground on a commercial demonstration plant capable of producing 10,000 metric tons per year by the end of 2027, focusing initially on supplying high-purity iron to domestic magnet manufacturers.¹³ By 2030, Meroueh aims to partner with established steel producers to deploy a 500,000-metric-ton facility, matching the output of modern commercial mini-mills.¹³ Even at that scale, domestic deployment will represent a modest slice of the 80 million metric tons of steel the United States produces each year, leaving the broader transformation of global heavy industry as an ongoing challenge.¹

This piece was prepared from published announcements, institutional reports, and public records; the founders and researchers have not been interviewed.

References

This article is based on 5 sources, listed in the order they are cited.

1. 1 BR Bridget Reed Morawski announcement · 8 Sep 2026 This founder is making cheaper, cleaner steel See the source
2. 2 H herthametals.com third party · 22 Jul 2025 Hertha Metals Unveils Breakthrough Process to Accelerate American-Made Steel and High-Purity Iron Production - Hertha Metals See the source
3. 3 N news.mit.edu A streamlined way to make steel could reduce America’s reliance on imports See the source
4. 4 O oreaco.com Hertha See the source
5. 5 H herthametals.com third party · 12 Jan 2025 Hertha Metals News | Latest Updates and Press Releases See the source