Can CO2 captured from blast furnace gases be recycled into steelmaking inputs?

Yes, COâ‚‚ captured from blast furnace gases can be recycled into steelmaking inputs. Plasma-based conversion technology makes it possible to split COâ‚‚ molecules back into carbon monoxide, which can then re-enter the blast furnace as a reducing agent, effectively closing the carbon loop within the steelmaking process itself. The sections below unpack how this works, what the technical and commercial barriers look like, and where the technology stands today.

How is COâ‚‚ currently generated in blast furnace steelmaking?

Blast furnace steelmaking generates COâ‚‚ as a direct byproduct of using coke, a carbon-rich fuel derived from coal, to reduce iron ore into molten iron. When coke reacts with oxygen inside the furnace, it produces carbon monoxide, which strips oxygen from iron ore. That carbon monoxide is then oxidized further into COâ‚‚, which exits the furnace as part of the off-gas stream. The result is one of the most carbon-intensive industrial processes on the planet.

Blast furnace off-gas is not pure COâ‚‚. It is a mixed stream that typically contains carbon monoxide, nitrogen, hydrogen, and COâ‚‚ in varying proportions. This complexity matters for downstream processing, because any recycling technology must either tolerate diluted COâ‚‚ inputs or include a separation step before conversion. The sheer volume of gas produced at a single integrated steel plant means that even partial COâ‚‚ recovery and conversion represents a significant decarbonization lever.

Steel production is responsible for roughly 7 to 9 percent of global COâ‚‚ emissions, with blast furnace-based production accounting for the overwhelming majority of that figure. The process is structurally carbon-intensive because carbon is not just an energy source in steelmaking, it is a chemical reactant. That distinction is what makes plasma COâ‚‚ conversion technology particularly relevant: it addresses the chemical role of carbon directly, rather than simply trying to capture and store emissions after the fact.

What does it mean to ‘recycle’ COâ‚‚ into a steelmaking input?

Recycling COâ‚‚ into a steelmaking input means chemically converting captured COâ‚‚ back into carbon monoxide, which can then be reinjected into the blast furnace as a reducing agent. Rather than treating COâ‚‚ as waste to be stored underground, this approach, known as Carbon Capture and Utilization (CCU), turns the molecule into a functional raw material that replaces fossil-derived inputs within the same industrial process.

The distinction between CCU and carbon capture and storage (CCS) is important here. CCS permanently sequesters COâ‚‚ underground, which removes it from the atmosphere but creates no economic value and requires ongoing storage infrastructure. CCU, by contrast, converts COâ‚‚ into something useful, in this case, carbon monoxide that performs the same chemical function as coke-derived CO inside the furnace. This means the steel plant reduces its need for new fossil carbon inputs while simultaneously managing its existing emissions.

In practical terms, recycling COâ‚‚ into a steelmaking input involves three steps: capturing COâ‚‚-rich off-gas from the blast furnace, converting that COâ‚‚ into carbon monoxide using an energy-efficient conversion process, and reinjecting the resulting CO into the furnace or using it elsewhere in the production chain. The carbon does not disappear, it circulates. This circular carbon approach is what makes the concept genuinely different from emissions reduction through efficiency gains or fuel switching alone.

How does plasma technology convert blast furnace COâ‚‚ into carbon monoxide?

Plasma technology converts COâ‚‚ into carbon monoxide by using high-energy plasma, an ionized gas state, to break the bond between carbon and oxygen atoms. Powered by renewable electricity, a plasma reactor creates conditions in which COâ‚‚ molecules are selectively dissociated into CO and atomic oxygen, without the need for fossil-based heat or chemical catalysts. The process produces no byproducts such as carbon black, and operates at ambient temperatures outside the plasma zone itself.

The underlying chemistry is straightforward: COâ‚‚ â†’ CO + Â½Oâ‚‚. What makes plasma the enabling technology is its ability to deliver the precise activation energy needed for this bond-breaking reaction with exceptional selectivity and efficiency. Conventional thermal methods require extremely high temperatures sustained over time, making them energy-intensive and difficult to integrate with variable renewable power sources. Plasma reactors, by contrast, can be switched on and off almost instantaneously, which makes them compatible with intermittent solar and wind electricity, a critical operational advantage as industrial sites increasingly source power from renewable grids.

D-CRBN’s Plasma ARCâ„¢ platform has demonstrated a 90.5% COâ‚‚ conversion rate in a single pass, with an energy requirement of 1,100 kWh per tonne of COâ‚‚. The technology is at least five times more energy-efficient than the reverse water-gas shift reaction, which is the conventional alternative for CO production. CAPEX is 50% lower than second-in-class alternatives, with the reactor’s main structural component being steel rather than rare-earth metals or complex geometries. The system can also handle diluted COâ‚‚ streams containing up to 50% nitrogen, which means it integrates directly with blast furnace off-gas without requiring a complete COâ‚‚ separation step upstream.

Can recycled COâ‚‚ actually replace coke in a blast furnace?

Recycled COâ‚‚ converted into carbon monoxide can partially replace coke’s chemical function in a blast furnace, specifically as a reducing agent for iron ore. Carbon monoxide is the active reducing species inside the furnace regardless of its origin, whether it comes from burning coke or from a plasma reactor fed with captured COâ‚‚. Reinjecting plasma-derived CO into the furnace therefore displaces a portion of the coke that would otherwise need to be consumed to generate that CO in the first place.

The degree of substitution is not one-to-one with coke as a physical fuel, because coke also provides structural support inside the furnace and contributes thermal energy. COâ‚‚-derived carbon monoxide addresses the chemical reduction function, not the structural or thermal roles. This means plasma-based CO recycling works as a complementary decarbonization measure rather than a complete replacement for coke in conventional blast furnace design. The practical outcome is a meaningful reduction in coal consumption and the associated COâ‚‚ emissions, rather than a full elimination of coke dependency in a traditional furnace configuration.

For steelmakers pursuing deeper decarbonization, the plasma CO route is particularly attractive because it does not require a wholesale redesign of existing assets. The electrified feedstock system integrates as a modular add-on, feeding CO back into the process stream without major capital write-offs or infrastructure overhauls. This plug-and-play characteristic is what makes the technology commercially viable in the near term, when most integrated steel plants are not yet ready to transition entirely to direct reduced iron (DRI) or hydrogen-based routes.

What are the main barriers to scaling COâ‚‚ recycling in the steel sector?

The main barriers to scaling COâ‚‚ recycling in the steel sector are energy cost and availability, COâ‚‚ stream quality, integration complexity, and the current economics of competing with fossil-derived carbon monoxide at scale. Each of these barriers is real but addressable, and the viability of plasma-based CCU depends heavily on access to affordable renewable electricity and a supportive carbon pricing environment.

Energy cost and renewable electricity access

COâ‚‚ conversion is an energy-intensive process, and the economics only work if the electricity input is both low-cost and low-carbon. At 1,100 kWh per tonne of COâ‚‚ converted, a plasma system running on expensive grid electricity may struggle to produce CO at a price competitive with fossil-derived alternatives. The business case strengthens considerably when the reactor operates on surplus renewable energy, periods when wind or solar generation exceeds grid demand and electricity prices fall sharply. D-CRBN’s instant on/off reactor design is engineered specifically for this use case, allowing steel plants to absorb renewable energy peaks and convert them into stored chemical value.

COâ‚‚ stream quality and capture infrastructure

Blast furnace off-gas contains COâ‚‚ alongside nitrogen, carbon monoxide, and hydrogen in proportions that vary by operating conditions. While plasma conversion can handle diluted COâ‚‚ streams, some degree of gas conditioning or pre-separation is typically needed before the gas enters the reactor. Steel plants that have not yet invested in off-gas capture and conditioning infrastructure face an additional capital requirement before COâ‚‚ recycling can begin. This is a sequencing challenge rather than a fundamental technical barrier, but it does affect the timeline and cost of first deployment.

Regulatory and carbon pricing alignment

The financial attractiveness of COâ‚‚ recycling is directly linked to the cost of emitting COâ‚‚ under the EU Emissions Trading System (ETS). As carbon prices rise, the avoided cost of emitting COâ‚‚, combined with the reduced need to purchase fossil feedstocks, makes the CCU investment case stronger. In environments where carbon pricing is low or uncertain, the economic incentive to invest in COâ‚‚ recycling infrastructure is correspondingly weaker. Policy stability and clear carbon pricing trajectories are therefore as important to scaling CCU in steel as the technology itself.

Which steelmakers are already testing COâ‚‚-to-feedstock conversion?

Industrial testing of plasma-based COâ‚‚-to-feedstock conversion in the steel sector has already moved beyond the laboratory. The first steel plant in the world to trial this process was ArcelorMittal Gent, where D-CRBN’s plasma reactor used renewable electricity to split COâ‚‚ captured from blast furnace off-gases. The resulting oxygen was consumed in-process to boost reactor efficiency, and the carbon monoxide produced was recycled as a feedstock in steelmaking, a closed-loop demonstration at industrial pilot scale.

This validation at an operating steel facility is significant because it confirms that plasma COâ‚‚ conversion is not a controlled laboratory result. The technology performed under real industrial conditions, processing actual blast furnace off-gas streams and integrating with live production infrastructure. For procurement teams and plant engineers evaluating CCU options, industrial validation at a major integrated steel plant represents a meaningful risk reduction compared with technologies that have only been proven at bench scale.

Beyond the steel sector, D-CRBN has advanced validation work with partners in the chemical sector as well, and multiple demonstration projects are progressing toward commercial deployment. The company’s modular deployment model, containerized systems that integrate directly with existing site infrastructure, is designed to reduce the friction of first adoption and accelerate the path from pilot to full-scale electrified feedstock production. Steel producers evaluating their decarbonization roadmap for the second half of this decade are increasingly looking at COâ‚‚ recycling not as a future option, but as a near-term commercial reality.

For industrial operators ready to explore on-site COâ‚‚ recycling, D-CRBN’s team works directly with plant engineers and sustainability leads to design deployment pathways suited to specific site conditions. The starting point is understanding your COâ‚‚ stream, volume, composition, and available renewable power, and matching those parameters to the right system scale. Get in touch with D-CRBN to begin that conversation.

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