Turning Steel Slag Green: How Biochar Is Revolutionizing the Steel Industry

jaryl3
Jun 15
3 min read

Updated: Jun 17

Biochar’s Hidden Role in Decarbonizing Steel Production

As the global steel industry faces pressure to reduce emissions, a quiet revolution is underway. Biochar, a carbon-negative material made from agricultural waste, is being adopted as a sustainable alternative to metallurgical coal and carbon injectants in steelmaking.

This article explores how biochar is being used in Electric Arc Furnaces (EAFs) and blast furnaces, how it can help decarbonize slag and byproducts, and why it’s increasingly viewed as a credit-generating material under international carbon frameworks.

Photorealistic image of biochar being used in a modern steel plant as a sustainable alternative to metallurgical coke. Highlights low-carbon industrial processes, biochar integration into furnaces, and decarbonization in heavy industry. — **Disclaimer:** This image is for illustrative purposes only. It does not represent actual product packaging, carbon content, or certified specifications. For verified biochar specifications and documentation, please contact Greenchar directly.

Where Biochar Fits in the Steelmaking Process

Steel mills generate large carbon footprints through both energy consumption and chemical reactions. Biochar can be introduced in several ways:

1. Carbon Injectant in Electric Arc Furnaces (EAFs)

Biochar is injected during EAF operations to:

Act as a foaming agent to protect the arc
Replace anthracite or coke as a carbon source
Improve slag dynamics and steel yield
Cut Scope 1 CO₂ emissions

📖 Reference: Lehmann et al., 2021 – Biochar Applications in Steelmaking

2. Partial Replacement of Coke in Blast Furnaces

Biochar with >70% fixed carbon and low ash content can replace a portion of coke, with studies showing:

Comparable calorific value (~24 MJ/kg)
Reduced emissions and heavy metal input
Potential for up to 30% CO₂ savings per ton steel

📖 Reference: Nunes et al., 2023 – Biomass Char as an Alternative to Coke in BF

3. Slag Conditioning

Biochar’s high alkalinity and porous structure allow it to:

Improve slag stability
Enhance slag use in cement or road base
Permanently sequester carbon within mineral matrices

📖 Reference: Wang et al., 2020 – Carbon Sequestration in Slag-Biochar Composites

Carbon Credit Potential in Steel + Biochar Projects

Biochar’s integration into industrial metallurgy can qualify for carbon credit methodologies focused on:

Biogenic carbon substitution (Puro.Earth, Verra under development)
Permanent carbon sequestration in slag (experimental MRV models)
CO₂ avoidance via fossil fuel replacement

While not yet mainstream in registries, Greenchar can help design and submit custom methodologies , MRV protocols or pilot credit-eligible projects.

Technical Specifications for Steel-Grade Biochar

When used in steel applications, biochar must meet strict parameters:

Property	Requirement
Fixed Carbon	> 70%
Moisture Content	< 8%
Volatile Matter	< 15%
Ash Content	< 10% (depends on slag tolerance, preferably <5%)
Particle Size	1–5 mm
H/C Ratio	< 0.7
Feedstock Source	Bamboo, hardwood, palm kernel shell

All batches from Greenchar are tested for:

Heavy metals (Pb, Hg, Cd, As)
pH and EC
O/C and H/C ratios for permanence verification

Real-World Case Studies:

Pilot at RWTH Aachen & Vietnam Steel Plant

RWTH Aachen Pilot (Germany): EAF tests showed no adverse effects on steel quality or melting when replacing fossil carbon with biochar .
Vietnam Steel Plant Pilot: Local steel mill replaced 15% of carbon injectants in EAF, achieving 18% CO₂ reduction while maintaining product quality. The project is currently undergoing carbon credit validation.