A new study reveals that biochar, a carbon-rich material increasingly promoted for sustainable agriculture, can significantly reduce methane emissions from rice paddies. However, its climate benefits depend strongly on how much nitrogen fertilizer is applied.
Rice cultivation is a major global source of methane, a potent greenhouse gas. As rice feeds nearly half of the world’s population, finding ways to reduce emissions without compromising food production is a critical challenge. In this new research, scientists combined large-scale data analysis with field experiments to better understand how biochar influences methane emissions in rice systems.
“Our results show that biochar has strong potential to mitigate methane emissions, but this benefit is not guaranteed,” said the study’s corresponding author. “It depends on how farmers manage nitrogen inputs.”
The research team analyzed 146 datasets from 51 independent studies worldwide, using advanced statistical approaches including network meta-analysis and machine learning methods. They compared different organic amendments commonly used in agriculture, such as straw, compost, manure, and biochar.
The findings were clear. Among all materials tested, biochar consistently showed the lowest methane emissions. In contrast, straw and manure tended to increase emissions significantly.
However, the study also uncovered an important caveat. The amount of mineral nitrogen fertilizer applied to fields emerged as the most influential factor controlling biochar’s effectiveness. When nitrogen inputs remained below approximately 291 kilograms per hectare, biochar reduced methane emissions. But when nitrogen levels exceeded this threshold, biochar actually increased methane emissions.
To validate these findings, the researchers conducted field experiments in a rice growing region in eastern China. The results confirmed the pattern observed in the meta-analysis. Under high nitrogen conditions, biochar significantly increased methane fluxes and emission potential compared to control treatments.
This counterintuitive effect may be explained by interactions between nitrogen, microbes, and carbon cycling in flooded soils. High nitrogen levels can stimulate plant growth and microbial activity, providing more substrates for methane-producing microorganisms. At the same time, excess nitrogen may suppress methane oxidation, tipping the balance toward higher emissions.
The study also identified another important factor: the carbon to nitrogen ratio of biochar itself. Biochar with lower ratios, typically derived from crop residues, showed stronger methane reduction potential. This suggests that both material design and field management must be considered together.
“These findings highlight that biochar is not a one-size-fits-all solution,” the authors noted. “Its climate benefits depend on aligning biochar properties with appropriate fertilizer management.”
The implications are significant for sustainable agriculture and climate mitigation. Biochar has been widely proposed as a carbon-negative technology that can improve soil health while reducing greenhouse gas emissions. This study suggests that its effectiveness in rice systems can be optimized through careful control of nitrogen inputs.
By integrating global data with real-world experiments, the research provides one of the most comprehensive assessments to date of how biochar interacts with agricultural management practices to influence methane emissions.
As policymakers and farmers look for practical ways to reduce agriculture’s climate footprint, the study offers a clear message. Biochar can be a powerful tool, but only when used under the right conditions.
“Optimizing nitrogen management is key to unlocking the full mitigation potential of biochar,” the authors said.
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Journal Reference: Huang, W., Liu, X., Deng, Y. et al. Mineral nitrogen input modulates the methane mitigation potential of biochar in rice systems: based on meta-analysis and field experiment demonstration. Biochar 8 , 60 (2026).
https://doi.org/10.1007/s42773-025-00563-y
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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Biochar
Experimental study
Mineral nitrogen input modulates the methane mitigation potential of biochar in rice systems: based on meta-analysis and field experiment demonstration
21-Feb-2026