Biochar from wood matches the strength of steel

November 01, 2025

Wood has long been valued for its beauty, resilience, and versatility — and now, it’s inspiring a revolutionary new form of carbon stronger than ever imagined.

A groundbreaking study from the University of Toronto has revealed that biochar made from wood can reach hardness levels comparable to mild steel — depending on the direction it’s tested.

Unlocking the strength hidden in wood’s structure

Researchers discovered that the orientation of biochar testing dramatically influences its hardness — by as much as 28 times. This directional difference, or anisotropy, arises from the natural grain and pore architecture preserved from the original wood.

The findings open new pathways for sustainable carbon-based materials with applications in energy storage, filtration, and lightweight structural systems — all made possible by nature’s design.

What is biochar?

Biochar is a carbon-rich substance produced when biomass, such as wood, is heated in the absence of oxygen — a process known as pyrolysis. Traditionally recognized for its role in soil improvement and pollution remediation, biochar’s mechanical potential has remained largely untapped — until now.

The new research challenges previous assumptions, positioning biochar not just as an environmental tool but as a high-performance, eco-friendly material for next-generation engineering.

Inside the experiment: turning wood into steel-like carbon

Led by Professor Charles Jia of the Green Technology Laboratory, the research team analyzed monolithic biochar — solid blocks that retain the wood’s original grain and pore structure.

Samples from seven species, including maple, pine, bamboo, and African ironwood, were heated between 600°C and 1,000°C. The results were striking:

• African ironwood biochar achieved an axial hardness of 2.25 gigapascals, matching that of mild steel.

• Hemlock biochar displayed extreme directional variation, with along-grain hardness exceeding cross-grain values by a factor of 28.5.

Using micro- and nano-indentation testing, the researchers confirmed that at the nanoscale, hardness remained consistent across species — suggesting that the cell-wall carbon structure is universally strong.

From renewable waste to high-performance material

The study also identified a clear link between hardness, density, and carbon content: denser biochar with higher carbon concentration proved significantly more resistant to deformation.

“Biochar is not just an environmental material — it’s a structural one,” said Professor Jia. “By preserving the natural architecture of wood, we can engineer carbon materials with customized mechanical properties for diverse industrial uses.”

A sustainable blueprint for future engineering

Potential applications include:

•  High-strength carbon electrodes for energy storage systems

•  Lightweight composites for aerospace and automotive industries

•  Directional flow filters for water and air purification

Engineers could even design materials that are rigid in one direction and flexible in another, emulating wood’s natural mechanical balance.

By decoding wood’s internal architecture, the University of Toronto team has laid the foundation for a new generation of biochar-based carbon materials that unite strength, sustainability, and design precision — a perfect harmony of nature and technology.