A study questions how long biochar really locks away carbon

A widely used scientific model may be underestimating the long-term climate benefits of biochar, according to a analysis published in Biochar. The study highlights critical flaws in how scientists currently estimate how long carbon remains stored in this charcoal-like material.

Biochar is increasingly promoted as a carbon dioxide removal strategy because it can store carbon in soils for hundreds to thousands of years. However, the new research suggests that the standard “two-pool” decay model used in policy and carbon markets may not accurately reflect how biochar behaves in the real world.

“Our findings show that current models may significantly overestimate how quickly biochar breaks down,” said lead author Hamed Sanei. “This could mean that biochar is actually more stable and more effective for long-term carbon storage than we previously thought.”

The commonly used model divides biochar into two components: a fast-decaying portion and a more stable fraction. But the authors found that the model assigns such a small proportion to the fast-decaying component that it effectively behaves like a single-pool system, applying higher decay rates to almost all biochar carbon. As a result, the model may exaggerate carbon loss over time.

The study also reveals that the model does not properly account for key factors known to influence biochar stability, such as production temperature and chemical structure. In reality, higher-temperature biochars tend to be more stable, yet this relationship is missing from current model assumptions.

Because most experimental studies only capture short-term decomposition, they primarily measure the loss of easily degradable carbon, leaving the long-term stability of more resistant carbon largely unknown.

The researchers call for improved models that better reflect biochar chemistry and incorporate data from long-term experiments and advanced analytical techniques.

By refining how biochar permanence is calculated, the study aims to strengthen confidence in its role as a reliable tool for climate mitigation.

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Journal Reference: Sanei, H., Petersen, H.I., Chiaramonti, D. et al. Evaluating the two-pool decay model for biochar carbon permanence. Biochar 7, 9 (2025).   

https://doi.org/10.1007/s42773-024-00408-0   

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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. 

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