Scientists craft biochar from wood waste that rivals steel in strength

Researchers at the University of Toronto have developed biochar made from wood waste that exhibits hardness comparable to mild steel, marking a significant advancement in sustainable materials. Their study reveals that the mechanical strength of biochar is highly anisotropic—varying by more than 28 times depending on the testing direction—due to the preserved natural grain and pore structure of the original wood. By heating different wood species, including African ironwood and hemlock, at temperatures between 600 °C and 1,000 °C, the team demonstrated that both wood type and pyrolysis conditions critically influence the resulting biochar’s strength, with African ironwood biochar reaching an axial hardness of 2.25 gigapascals. This research challenges the traditional view of biochar solely as an environmental aid for soil improvement and pollutant cleanup, positioning it instead as a promising structural material for green engineering. The findings highlight that the wood’s intricate pore network—not the carbon itself—drives the direction-dependent mechanical properties,