Biochar shows strong promise for locking more carbon in soils, global review finds
A global analysis suggests biochar can substantially increase soil carbon sequestration, while its effects on soil CO2 flux and microbial respiration remain less certain
image: Biochar’s effect on the soil carbon cycle: a rapid review and meta-analysis
Credit: Madina Bekchanova, Tom Kuppens, Ann Cuypers, Marijke Jozefczak & Robert Malina
As the world searches for practical ways to slow climate change, soil is gaining attention as one of Earth’s most important carbon reservoirs. A review and meta-analysis published in Biochar suggests that biochar, a carbon-rich material made by heating biomass under limited oxygen, could significantly improve the ability of soils to store carbon.
The study, led by Madina Bekchanova and colleagues, analyzed 75 peer-reviewed studies and 250 observations from around the world to examine how biochar affects three major components of the soil carbon cycle: total CO2 flux, total microbial respiration, and carbon sequestration. The results show that biochar increased soil carbon sequestration by an average of 61%, with a confidence interval of 36% to 90%. In contrast, biochar’s effects on total CO2 flux and microbial respiration were not statistically significant.
“Soils are not just a place where crops grow. They are active carbon systems that can either release carbon to the atmosphere or help store it for the long term,” said the study’s lead author. “Our analysis shows that biochar has clear potential to strengthen soil carbon storage, but its effects depend strongly on how and where it is used.”
Biochar is produced from materials such as crop residues, wood, or manure through pyrolysis. Because of its stable, aromatic carbon structure, biochar can remain in soil for long periods and may help delay the return of carbon to the atmosphere. This makes it an attractive option for climate mitigation, sustainable agriculture, and soil improvement.
However, the study also highlights that biochar is not a one-size-fits-all solution. Its effects varied depending on experimental design, geographic region, application rate, feedstock type, and pyrolysis temperature. Incubation experiments generally showed stronger responses than field or greenhouse experiments, likely because laboratory conditions are more controlled. The authors found that the Middle East, Europe, and Asia showed notable potential for improving carbon sequestration with biochar.
Application rate also mattered. Higher biochar application rates tended to increase carbon sequestration and microbial respiration. Feedstock type played an important role as well. Biochar made from manure and digestate was linked to higher microbial respiration, while woody biochar was associated with greater CO2 flux. Lower pyrolysis temperatures showed promise for improving carbon sequestration and microbial respiration, although the authors caution that more studies are needed because the number of observations in this category was limited.
The findings help clarify a key question in climate-smart agriculture: whether biochar can improve soil carbon storage without unintentionally increasing carbon losses. According to the authors, the answer is promising but nuanced. Biochar significantly improved carbon sequestration overall, yet its impacts on CO2 release and microbial activity were inconclusive.
“These results suggest that biochar can be a valuable tool for carbon management, especially when its production conditions and application strategies are carefully matched to soil and climate conditions,” the lead author said. “Future studies should focus more on long-term field evidence so that farmers, land managers, and policymakers can make better decisions.”
The authors emphasize that optimizing biochar use will require more region-specific and soil-specific research. While laboratory studies provide important mechanistic insight, field conditions involve more complex factors such as crop growth, tillage, erosion, leaching, soil moisture, and microbial community shifts.
Overall, the study supports biochar as a promising soil amendment for carbon sequestration, but also calls for careful management and further long-term research. As agriculture faces growing pressure to reduce greenhouse gas emissions while maintaining productivity, biochar may become an important part of a broader strategy to build healthier soils and a more stable climate.
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Journal Reference: Bekchanova, M., Kuppens, T., Cuypers, A. et al. Biochar’s effect on the soil carbon cycle: a rapid review and meta-analysis. Biochar 6, 88 (2024).
https://doi.org/10.1007/s42773-024-00381-8
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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.