A new global analysis suggests that the climate mitigation potential of biochar could be overestimated if warming-driven carbon losses are not considered, especially in agricultural soils.
Biochar, a carbon-rich material produced by heating plant or animal residues in low-oxygen conditions, has attracted growing attention as a promising tool for improving soil health and storing carbon. But as the planet warms, scientists are asking a critical question: will biochar-amended soils continue to hold carbon as effectively under higher temperatures?
A new study published in Biochar provides an important warning. By analyzing 2079 paired observations from 32 peer-reviewed studies, researchers found that warming significantly increased carbon dioxide emissions from soils treated with biochar. Across all ecosystems, warming raised CO₂ emissions from biochar-amended soils by an average of 77%. The effect was especially strong in croplands, where emissions increased by 117.5%, compared with 30.9% in forest soils.
"Our findings do not mean biochar is ineffective," said corresponding author Junjie Lin. "They show that biochar strategies must be designed with climate warming in mind. Without considering warming effects, we may overestimate how much carbon biochar can help store in agricultural soils."
The study highlights a major concern for cropland management. Agricultural soils are often disturbed by tillage, irrigation, and fertilization, which can make soil organic carbon more accessible to microbes. Under warmer conditions, microbial activity can accelerate the breakdown of soil carbon and biochar-associated carbon, releasing more CO₂ back into the atmosphere.
Warming magnitude was the strongest driver of increased CO₂ emissions, outweighing the effects of soil properties and biochar characteristics. However, the type and application of biochar also mattered. Woody biochars triggered stronger warming responses than crop- or grass-derived biochars. Higher pyrolysis temperatures, higher application rates, smaller particle sizes, and certain soil properties were also linked to greater warming-induced CO₂ release.
"These results suggest that one-size-fits-all biochar recommendations are not enough," said co-corresponding author Fei Li. "Farmers, land managers, and policymakers need site-specific guidance that considers land use, soil conditions, biochar feedstock, production temperature, and expected warming."
The authors suggest several practical strategies to help reduce the risk of warming-driven carbon loss. These include using non-woody feedstocks such as crop residues or grasses, producing biochar at lower or moderate pyrolysis temperatures, and applying biochar at optimized rather than excessive rates. Croplands, where the warming response was strongest, may require stricter management and closer monitoring.
The findings also have implications for climate accounting. Biochar is increasingly included in carbon removal and soil carbon management frameworks, but many life-cycle assessments may not fully account for how future warming could alter soil CO₂ emissions. The authors argue that warming effects should be integrated into biochar life-cycle assessments and soil carbon models to produce more realistic estimates of biochar's climate benefits.
The study also notes important data gaps. Many available observations come from laboratory experiments and temperate regions, while tropical, polar, arid, semi-arid, and high-latitude ecosystems remain underrepresented. More field studies with realistic warming gradients are needed to better understand how biochar performs under real climate change conditions.
The message is clear: biochar remains a valuable tool for sustainable soil management, but its climate benefits depend on how and where it is used. In a warming world, smarter biochar design and region-specific application guidelines will be essential for ensuring that biochar contributes effectively to carbon sequestration and climate mitigation.
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Journal Reference: Xu, T., Xu, Q., Lei, Y. et al. Warming increases CO2 emissions in biochar-amended cropland soil. Biochar 8, 106 (2026).
https://doi.org/10.1007/s42773-026-00628-6
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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.
