Warming May Weaken Biochar’s Climate Benefits in Cropland Soils, Global Study Finds

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.

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.