Biochar in EAF Steelmaking: Cutting CO₂ by 20.9% Per Tonne
New research shows wood biochar in EAF steelmaking cuts CO₂ by 20.9% at 25.6 kg/t. See the costs, feedstock trade-offs and what it means for buyers.
New research in Ironmaking & Steelmaking: Processes, Products and Applications shows that biochar in EAF steelmaking can cut carbon emissions significantly without redesigning the furnace. In a detailed case study of mass, energy and emissions, wood biochar replaced coke fines at 25.6 kg per tonne of crude steel and reduced CO₂ emissions by 20.9%.
For procurement managers and sustainability officers, the study answers the questions that matter most: which biochar works, how much is needed and what it costs. It also shows that the choice of feedstock can make or break the business case.
Why Electric Arc Furnaces Still Depend on Fossil Carbon
Electric arc furnaces (EAFs) melt scrap steel or direct reduced iron using powerful electric arcs. Because they run on electricity rather than blast furnace coke, EAFs are widely seen as the lower-carbon route to steel.
EAFs still emit carbon, though. Most operations add coke fines, which are small particles of coal-derived coke. The fines supply chemical energy and help form foamy slag, a layer that shields the furnace and improves energy efficiency. Many plants also use natural gas burners to speed up melting.
In the case study, the baseline furnace used 359.3 kWh of electricity per tonne of crude steel. Any input that moves that number up or down directly affects operating cost and the indirect emissions that come from grid power.
How Biochar in EAF Steelmaking Performs
Biochar is a carbon-rich solid made by heating biomass with little or no oxygen, a process called pyrolysis. Its carbon comes from plants that recently absorbed CO₂ from the atmosphere, so it can replace fossil carbon with a much lower climate impact. For background, see our [link:what-is-metallurgical-biocarbon] guide.
The researchers modeled three types of biochar as substitutes for coke fines:
| Biochar feedstock | Replacement rate (kg/t crude steel) | Change in power use (kWh/t) |
|---|---|---|
| Wood biochar | 25.6 | -4.2 |
| Rice husk biochar | 39.4 | +41.5 |
| Corn stover biochar | 60.0 | +63.0 |
Wood biochar is the clear frontrunner
Wood biochar was the only option that reduced power consumption, taking 4.2 kWh/t off the 359.3 kWh/t baseline. It also delivered the strongest climate result: a reduction of 83.8 kg CO₂ eq per tonne of crude steel, or 20.9%.
The study names wood biochar as the most viable substitute, with minimal power consumption trade-offs.
Feedstock Selection: Why Not All Biochar Is Equal
For buyers, the most practical finding is the gap between feedstocks. Rice husk biochar raised power demand by 41.5 kWh/t, and corn stover biochar raised it by 63 kWh/t.
Both agricultural biochars also need much more material to do the same job. Corn stover biochar requires 60.0 kg/t, more than twice the wood biochar rate. That means more material to buy, ship, store and feed into the furnace.
Agricultural residues usually contain more ash (non-combustible mineral content) than wood, which probably explains part of the difference in furnace performance. The takeaway for procurement teams is simple:
- Specify the feedstock in supply contracts, not just biochar
- Request fixed carbon and ash content data for every lot
- Be cautious with lower-priced, high-ash products, because extra power use can wipe out the savings
- Choose feedstock based on regional availability only after confirming how it performs in the furnace
Our [link:biochar-specifications-guide] explains the key quality parameters in more detail.
Adding Biomethane for a Combined Pathway
The study also looked at biomethane, a renewable gas made from organic waste that is chemically similar to natural gas. Replacing fossil natural gas took 4.51 Nm³ of biomethane per tonne of steel, supplying 136.6 MJ/t of energy.
The cost impact was small, at only 0.4–1.6 USD per tonne. That makes biomethane an easy first step for many EAF operators.
With biomethane and wood biochar deployed together, total emissions fell by 92.7 kg CO₂ per tonne of steel. Neither change required a fundamental furnace redesign, which shortens the path from pilot to full production.
What Does Biomass Substitution Cost?
Decarbonization is rarely free, and the study is open about the cost. Depending on the biochar feedstock, substitution added $7 to $23 per tonne to production costs.
| Metric | Value |
|---|---|
| Biomethane cost impact | 0.4–1.6 USD/t steel |
| Biochar substitution cost premium | 7–23 USD/t steel (depends on feedstock) |
| Wood biochar CO₂ reduction | 83.8 kg CO₂ eq/t (20.9%) |
| Biomethane + wood biochar reduction | 92.7 kg CO₂/t |
Producers facing carbon pricing should weigh this premium against the cost of the emissions it avoids. The study describes biomass substitution as economically competitive for facilities that prioritize emissions reduction.
What This Means for CBAM and ESG Compliance
The EU Carbon Border Adjustment Mechanism (CBAM) puts a price on the embedded emissions of imported steel, in line with what domestic producers pay under the EU Emissions Trading System (EU ETS). Lower-emission steel is becoming a commercial advantage, not just a line in a report.
For sustainability officers, using wood biochar in the EAF gives a measurable, process-level reduction that can be documented per tonne. For that reduction to count, buyers should:
- Secure a consistent, traceable supply of wood biochar
- Keep chain-of-custody records showing where the biomass came from and that it was sustainably sourced
- Use carbon accounting methods that match the reporting frameworks customers and regulators rely on
For a deeper look at reporting, read our [link:cbam-steel-compliance-guide].
Conclusion
This case study gives one of the clearest pictures yet of how biochar performs in EAF steelmaking under real process constraints. Wood biochar stands out: 25.6 kg/t replaces coke fines, power use drops slightly and emissions fall by 20.9%. Combined with biomethane, reductions reach 92.7 kg CO₂ per tonne.
For buyers, the main lesson is that feedstock quality drives results. Decarbonization starts with sourcing the right biochar with verified specifications.
Explore verified biochar suppliers on BiocharLink and compare wood biochar specifications side by side in our [link:biochar-marketplace].
Source: A case study on biomass steelmaking in electric arc furnaces: Mass, energy and emission analysis. Ironmaking & Steelmaking: Processes, Products and Applications. https://doi.org/10.1177/03019233261429765