Asphalt pavements dominate global road networks due to fast construction times and exceptional structural adaptability. However, conventional petroleum-derived asphalt binders generate high carbon footprints during production while releasing toxic fumes—including volatile organic compounds, polycyclic aromatic hydrocarbons, and hydrogen sulfide gas—during high-temperature mixing and paving operations. To resolve these environmental and health challenges, road engineering has turned to biochar as a sustainable, carbon-rich asphalt modifier derived from pyrolyzed agricultural and forestry residues.

Integrating biochar into asphalt materials significantly improves mechanical performance and durability across pavement applications. At suitable addition rates, biochar increases asphalt complex shear modulus and rotational viscosity, providing substantial skeletal reinforcement against high-temperature rutting deformation. Beyond mechanical strengthening, biochar enhances asphalt-aggregate interfacial adhesion by raising surface free energy, creating mechanical interlocking networks, and providing strong resistance against moisture-induced stripping and water damage. Biochar also serves as a protective anti-aging agent by trapping volatile light oils, scattering harmful ultraviolet rays, and quenching oxidative free radicals to keep pavement flexible over time.

The core breakthrough of recent research lies in using green activation techniques to transform biochar into a highly selective pollutant capture medium. While unmodified biochars rely mostly on physical pore confinement to trap small gaseous molecules, surface activation introduces tailored functional groups and metal active sites that chemically target complex pollutants. For example, green activation with tannic acid or phytic acid equips biochar with polyphenolic structures and reactive phosphorus sites that capture polar gases and aromatic hydrocarbons far more efficiently than raw carbon frameworks, outperforming high-dosage raw biochar additions.

Despite these environmental advantages, successful biochar-modified asphalt application depends strictly on precise dosage control and uniform material dispersion. Excess biochar addition or particle agglomeration can unacceptably increase binder viscosity, promote phase separation, and severely degrade low-temperature cracking resistance and fatigue life under cold-weather thermal stress. Furthermore, true sustainability requires evaluating biochar-modified asphalt across complete life-cycle boundaries—accounting for biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More collection energy, transport logistics, and potential pollutant leaching—to guarantee genuine long-term climate benefits and environmental safety.

Source: Ke, Y., Pang, E., Gustave, W., Gu, B., Chen, H., Song, Y., Lin, W., Zhang, X., & He, F. (2026). Performance tailoring and environmental implications of biochar-modified asphalt materials: Toward sustainable road design. Infrastructures, 11(9), Article 305.