How do steel producers use carbon monoxide from CO2 recycling?

Steel producers use carbon monoxide from CO₂ recycling as a direct reducing agent inside the blast furnace, replacing a portion of the coke-derived CO that has traditionally driven ironmaking. By converting captured CO₂ off-gases back into usable carbon monoxide through plasma-based CO₂ recycling, steel plants can close the carbon loop on-site, cut fossil feedstock consumption, and lower their exposure to EU Emissions Trading System costs, all without rebuilding existing infrastructure.

The sections below unpack how CO functions inside a furnace, where it has historically come from, how modern CO₂ recycling changes that equation, and which production routes are best positioned to benefit.

How is carbon monoxide used inside a blast furnace?

Carbon monoxide is the primary reducing agent in blast furnace ironmaking. It reacts with iron ore, iron oxides such as hematite and magnetite, stripping away the oxygen to produce liquid iron and carbon dioxide as a byproduct. Without a steady supply of CO at the right concentration and temperature, the reduction reactions that convert ore into metal simply cannot proceed.

The chemistry is straightforward: CO donates its carbon to the oxygen bound in iron oxide, producing metallic iron and CO₂. This reaction happens at multiple temperature zones as the burden descends through the furnace shaft. In the upper, cooler zones, indirect reduction by CO dominates. In the lower, hotter zones, direct reduction by solid carbon also plays a role, but gaseous CO remains the workhorse throughout.

What makes CO indispensable, rather than hydrogen or other reductants, is its ability to operate across a wide temperature window, its compatibility with existing furnace gas management systems, and the fact that the CO₂ it generates is already captured in the off-gas stream. That off-gas, known as blast furnace gas, is rich in CO, CO₂, and nitrogen, and is typically recycled within the plant for energy recovery. This creates a natural integration point for carbon monoxide from CO₂ recycling: the CO₂ already exits the furnace in a concentrated, capturable stream.

Where does carbon monoxide in steel plants traditionally come from?

Traditionally, carbon monoxide in steel plants is produced by the combustion and gasification of coke, a form of purified carbon derived from coking coal, inside the blast furnace. Hot air blown through tuyeres at the base of the furnace reacts with coke to form CO₂, which then reacts with more coke higher in the furnace to produce CO. The result is a reducing gas atmosphere that drives ironmaking.

Coke is therefore both a structural support for the burden inside the furnace and the chemical source of the CO that does the actual reduction work. This dual role makes coke difficult to eliminate entirely from conventional blast furnace operations, and it is the reason why the steelmaking sector remains one of the most carbon-intensive industries globally.

Beyond the blast furnace itself, steel plants also generate CO-rich process gases from coke ovens and basic oxygen furnaces. These gases are partially recirculated for heating and power generation within the plant, but a significant fraction is still vented or flared. The fossil origin of all this carbon monoxide means that every tonne of iron produced through the conventional route carries a substantial CO₂ footprint, and a corresponding ETS liability for producers operating in Europe.

How does CO₂ recycling produce carbon monoxide for steel plants?

CO₂ recycling produces carbon monoxide by breaking the bond between carbon and oxygen in CO₂ molecules, using energy rather than fossil carbon as the driving force. In plasma-based systems, renewable electricity energizes a plasma field that selectively activates CO₂, splitting it into CO and atomic oxygen. The result is a stream of carbon monoxide that can feed directly back into steelmaking without any fossil input at the conversion stage.

D-CRBN’s patented Plasma ARC™ technology is a validated example of this approach. The system captures CO₂-rich off-gases from blast furnace operations and passes them through a plasma reactor powered by renewable electricity. The process achieves a 90.5% CO₂ conversion rate in a single pass, with an energy requirement of 1,100 kWh per tonne of CO₂, making it at least five times more efficient than conventional reverse water-gas shift routes. Critically, the process produces no byproducts such as carbon black, and it operates at ambient temperatures, which reduces thermal stress on reactor components and lowers maintenance demands.

The plasma reactor design is inherently flexible. It can switch on and off rapidly, allowing it to consume surplus renewable electricity during periods of high wind or solar generation, effectively storing intermittent green energy as chemical feedstock. For a steel plant, this means the electrified CO production system can be sized and scheduled around both process gas availability and electricity pricing, maximizing the economic case without disrupting core operations.

Deployment follows a modular, plug-and-play model. The system integrates directly into existing gas infrastructure, processes diluted CO₂ streams containing up to 50% nitrogen, and requires no plant rebuild. For steel producers evaluating Carbon Capture and Utilization pathways, this lowers both the capital commitment and the operational risk of adoption considerably.

What are the cost and carbon advantages for steel producers?

Steel producers that adopt CO₂ recycling to generate carbon monoxide gain two compounding advantages: lower feedstock costs relative to fossil-derived CO, and a reduced CO₂ footprint that directly cuts ETS compliance costs. Both benefits strengthen the competitive position of the plant without requiring a switch to an entirely different production route.

Feedstock cost and price stability

Conventional CO production is tied to coking coal and natural gas prices, both of which are subject to geopolitical volatility and long-term supply uncertainty. Electrified CO production from recycled CO₂ decouples feedstock cost from fossil commodity markets. When the electricity input comes from renewable sources, particularly during periods of grid oversupply, the effective cost of producing CO can be highly competitive with fossil-derived alternatives. D-CRBN’s plasma technology carries a CAPEX 50% lower than second-in-class reverse water-gas shift systems and an OPEX 30% lower, driven by high energy efficiency and conversion rates. These economics are not marginal improvements; they represent a structural cost advantage that allows recycled CO to compete on price rather than relying on a sustainability premium.

Carbon footprint and ETS exposure

Every tonne of CO₂ that is recycled into carbon monoxide on-site is a tonne that does not need to be reported as an emission, or purchased as an allowance under the EU ETS. As carbon prices remain a material cost for European steel producers, the ability to convert point-source CO₂ into a productive input rather than a liability has a direct bottom-line impact. The lower carbon footprint of the resulting steel also strengthens the producer’s position in markets where customers are beginning to demand product-level carbon disclosure and low-carbon certification. Explore the full plasma conversion technology to understand how the process integrates into existing carbon accounting frameworks.

Which steel production routes are compatible with recycled carbon monoxide?

Recycled carbon monoxide from CO₂ recycling is compatible with both blast furnace-basic oxygen furnace (BF-BOF) routes and, to a growing degree, direct reduction-based routes that use syngas as a reductant. The integration pathway differs by route, but neither requires a fundamental redesign of the core production process.

In the BF-BOF route, which still accounts for the majority of global steel output, the blast furnace already operates on a carbon monoxide-rich atmosphere. Recycled CO produced on-site from captured blast furnace off-gases can be reinjected into the gas circuit, partially replacing the coke-derived CO and reducing the quantity of coke required per tonne of iron. This is the model validated at the first industrial plasma trial in the steel sector, where D-CRBN’s reactor used renewable electricity to split CO₂ captured from blast furnace off-gases and returned the resulting carbon monoxide as a steelmaking feedstock. The oxygen co-produced in the splitting reaction was consumed in-process, adding further efficiency.

For direct reduction routes, the relevant product shifts from pure CO to syngas, a mixture of CO and hydrogen, which serves as the reductant in shaft furnaces producing direct reduced iron. D-CRBN’s plasma systems can also process CO₂ alongside methane to produce syngas without fossil-based inputs or external hydrogen supply. This makes the technology relevant for producers transitioning toward lower-carbon direct reduction pathways, where syngas composition flexibility is a key operational requirement. The electrified syngas production pathway addresses this need directly.

Across both routes, the common requirement is a reliable source of CO₂-rich off-gas, something blast furnaces and direct reduction plants generate in abundance. The modular deployment model means producers can start at a scale below 100 ktpa CO and expand as confidence in the technology builds, without committing to large upfront infrastructure changes. For plants ready to move from evaluation to deployment, the logical next step is to discuss an electrified feedstock solution tailored to the specific gas streams and production volumes of the site.

Steel producers operating under tightening carbon regulation and facing long-term fossil feedstock risk have a concrete, proven option available today. CO₂ recycling through plasma conversion turns the blast furnace’s own emissions into the reducing agent that keeps it running, a circular model that is both technically sound and commercially competitive. To explore how this fits your operations, get in touch with D-CRBN directly.

Electrified CO

Electrified SYNGAS

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