Our technology

Step 1. Input materials

The technology is designed to process a wide range of oxidised materials, including ores, slags, mill scale, and other oxidised metal-bearing residues. While adaptable to diverse feedstocks, GreenIron’s initial focus is mill scale generated by the steel industry.

Step 2. Pre-processing

If the input material consists of fine particles, it is first agglomerated into larger units using a suitable binder. Forming briquettes, pellets, or extrudates ensures proper gas permeability during the subsequent heating and reduction stage.

The prepared batch with input material is charged into a perforated metal bucket, allowing process gases to flow uniformly through the material and onward to the heat recovery system. The batch is pre-heated to minimise processing time and optimise conditions for the subsequent reduction step.

Step 3. Reduction

The reduction stage is the core of GreenIron’s technology.

What is reduction?
Metals in ores and residues rarely occur in pure, usable form for steel production. Reduction is the chemical process in which oxygen is removed, enabling the recovery of pure metal. Traditionally, this has been carried out in blast furnaces or other fossil-based processes associated with significant CO₂ emissions.

The bucket with the prepared batch is placed inside the GreenIron reduction furnace and heated to approximately 600 °C. The furnace atmosphere is first flushed with nitrogen (N₂) to eliminate residual oxygen. Hydrogen gas (H₂) is then introduced, initiating the reduction reaction.

Hydrogen acts as the reducing agent, reacting with and removing oxygen from the material. The released oxygen then combines with hydrogen to form water (H₂O) as the only by-product.

The system is designed to operate efficiently using gravity, controlled temperature, and pressure variations. It is also circular and energy-efficient: outgoing process gases transfer heat to the incoming hydrogen stream, minimising heat loss and reducing overall energy demand.

Step 4. Customer product

Once the reduction process is complete, the finished batch is cooled, stored, and packaged for dispatch to the customer for use in steelmaking.

The recovered metal retains the original chemical composition of the input material – oxidised scale is converted back into metallic form. This enables steel producers to have their own by-products reduced and recycled, allowing seamless reintroduction into production, enhanced circularity, and improved material yield.

What makes GreenIron’s technology different?

Hydrogen-based reduction

Hydrogen enables carbon neutral reduction while producing only water as a by-product, unlike traditional blast furnace processes or other fossil based processes that rely on coke and emit CO₂.

Batch-based flexibility

The batch-based process allows different materials and compositions to be processed within the same system, providing high operational flexibility.

Modular furnace design

Each GreenIron furnace has a small footprint and is designed for modular deployment, enabling:

• Local processing close to steel plants
• Stepwise, scalable expansion

Resilient operation

The process can operate effectively with intermittent power, making it well suited for integration with renewable energy systems.

Materials and Flexibility

GreenIron’s technology can process a wide range of metal oxides and residual materials, including:

• Iron-based residuals e.g. mill scale and filter dust
• Oxides containing nickel, copper and molybdenum

GrenIron’s near-term focus is on steel industry by-products, with the technology designed to expand into additional segments over time.

Validation and Industrial Readiness

GreenIron’s technology has been validated through extensive R&D and industrial development:

• Patented process and system design
• R&D furnace in operation since 2020
• First full-scale commercial facility in Sandviken, Sweden since 2025.