A study highlights hidden environmental risks of biochar use
image: Challenges in safe environmental applications of biochar: identifying risks and unintended consequence
Credit: Mingying Dong, Mengyuan Jiang, Lizhi He, Zirun Zhang, Williamson Gustave, Meththika Vithanage, Nabeel Khan Niazi, Bo Chen, Xiaokai Zhang, Hailong Wang & Feng He
Biochar has been widely promoted as a sustainable solution for improving soil health, cleaning polluted water, and capturing carbon. However, a comprehensive review warns that its environmental safety may be more complex than previously thought.
In a study published in Biochar, researchers systematically examined the potential risks associated with the production and environmental application of biochar, a carbon rich material derived from heating biomass under low oxygen conditions. While its benefits have been extensively studied, the authors argue that unintended consequences require greater attention to ensure safe and sustainable use.
“Biochar is often seen as an environmentally friendly material, but its risks depend strongly on how it is produced and used,” said lead author Mingying Dong. “Understanding these risks is essential for guiding its safe application in agriculture and environmental management.”
Over the past decade, biochar has gained global popularity due to its ability to improve soil fertility, immobilize pollutants, and reduce greenhouse gas emissions. Its porous structure and large surface area make it highly effective at adsorbing contaminants such as heavy metals and organic pollutants. However, the new review reveals that biochar can also act as a source and carrier of harmful substances.
The researchers categorize these risks into two main types. The first involves pollutants that originate within the biochar itself. These may include heavy metals from contaminated feedstocks, toxic organic compounds such as polycyclic aromatic hydrocarbons formed during high temperature processing, and environmentally persistent free radicals that can generate reactive oxygen species. These substances may be released into soil and water, posing risks to ecosystems and human health.
The second type of risk arises after biochar is applied to the environment. Due to its strong adsorption capacity, biochar can accumulate pollutants from surrounding soil or water. While this reduces pollutant mobility in the short term, the contaminants may remain bioavailable and potentially harmful. Environmental aging processes, such as exposure to sunlight, rainfall, and microbial activity, can further alter biochar properties and lead to the gradual release of previously trapped pollutants.
The study also highlights the growing concern surrounding nanobiochar, tiny particles that can form as biochar breaks down over time. These particles are highly mobile and can travel through soil, enter groundwater, and even be taken up by plants. This raises questions about potential impacts on food safety and ecological systems.
Beyond environmental transport, the review examines the biological effects of biochar on plants, animals, microorganisms, and humans. While moderate applications can benefit soil ecosystems, excessive or contaminated biochar may inhibit plant growth, disrupt microbial communities, and harm soil organisms. Inhalation of fine biochar particles during handling may also pose respiratory risks.
To address these challenges, the authors emphasize the need for improved risk assessment and management strategies. They propose a framework that considers feedstock selection, production conditions, and environmental context to evaluate biochar safety. Tools such as chemical analysis, toxicity testing, and environmental modeling can help predict potential risks before large scale application.
“Biochar has great potential, but it should not be treated as a one size fits all solution,” the authors note. “Careful design, testing, and regulation are necessary to maximize benefits while minimizing unintended consequences.”
The findings provide important guidance for researchers, policymakers, and industry stakeholders working to develop safer and more sustainable biochar technologies.
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Journal Reference: Dong, M., Jiang, M., He, L. et al. Challenges in safe environmental applications of biochar: identifying risks and unintended consequence. Biochar 7, 12 (2025).
https://doi.org/10.1007/s42773-024-00412-4
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About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.