The world’s permafrost regions—vast areas where soil remains frozen for years—hold one of the largest and most unstable carbon reserves on the planet. As global temperatures rise, this frozen ground begins to thaw, releasing ancient stores of soil organic carbon (SOC) back into the atmosphere as CO2​ and CH4​, potentially accelerating climate change. Scientists are racing to find sustainable strategies to lock this carbon back down. A recent study published in the journal Carbon Balance and Management by Haiyin Wu, Shuying Zang, Hanxi Wang, and Dianfan Guo addresses this challenge by evaluating the impact of biochar on carbon sequestration in the vulnerable Daxing’anling permafrost region of Northeast China.

The researchers conducted a controlled, year-long incubation experiment using two representative soil types from the region: low-carbon forest soil and high-carbon peatland soil. They amended the soils with an 8% weight-to-weight (w/w) application of corn straw-derived biochar, a form of charcoal produced by heating agricultural waste. The results confirmed the material’s remarkable dual potential: biochar not only significantly increased the soil’s ability to store carbon but also substantially reduced the rate at which greenhouse gases were released.

The most striking impact was observed in the forest soils. After 360 days of monitoring, biochar addition increased the total Soil Organic Carbon (SOC) content by an impressive 60.57%. This stabilization translated directly into climate mitigation: cumulative CO2​ emissions from the forest soil were cut by 19.37% overall. The mitigation effect was especially potent during the simulated freeze-thaw periods, such as the spring thaw, where CO2​ emissions were reduced by as much as 33.61%. The biochar also significantly improved the soil’s physicochemical health, for instance, increasing electrical conductivity in the forest soil by 166.62%.

How does biochar achieve this profound stability? The key lies in its physical and chemical properties. Biochar is highly porous and recalcitrant—meaning it resists microbial breakdown. The researchers used advanced carbon isotope tracing (δ13C) to track the fate of the added carbon. They found that biochar significantly enhanced the formation of Mineral-Associated Organic Carbon (MAOC). MAOC is the most stable fraction of carbon, physically protected by binding to mineral particles and soil aggregates. In the forest soils, biochar caused MAOC to increase by a substantial 175.89% by the end of the second cycle, effectively locking the native soil carbon into long-term storage. This locking mechanism is so effective that the authors calculated the theoretical persistence of the added biochar in the forest soil at approximately 875 years.

However, the study highlighted that biochar’s effectiveness is highly dependent on the soil type. In the high-carbon peatland soil, the benefits were less pronounced compared to the forest soil. While peatland SOC still increased, the effect was marginal at 5.64%. Likewise, the reduction in CO2​ emissions in peatland was lower, at 9.70%. This difference is largely due to the initial soil properties. Peatland already contains massive amounts of stable organic carbon, meaning the microbial communities are less sensitive to biochar’s effects. The persistence of biochar in the peatland was also estimated to be shorter, at around 527 years. The study also found that biochar reduced the diversity and richness of bacterial communities in the forest soils, a finding that supports the idea that the microbes responsible for breaking down carbon were suppressed.

This research provides vital, context-specific data supporting biochar’s role as a practical and enduring solution for climate change mitigation. By successfully demonstrating that cost-effective agricultural waste can be converted into a soil amendmentA soil amendment is any material added to the soil to enhance its physical or chemical properties, improving its suitability for plant growth. Biochar is considered a soil amendment as it can improve soil structure, water retention, nutrient availability, and microbial activity.   More that cuts CO2​ emissions and stabilizes carbon for centuries, the study offers a powerful scientific basis for developing carbon management strategies in globally critical permafrost ecosystems. Future efforts should focus on tailoring biochar application rates based on specific soil characteristics to maximize these benefits.

Source: Wu, H., Zang, S., Wang, H., & Guo, D. (2025). Impact of biochar on carbon sequestration in permafrost region of Northeast China. Carbon Balance and Management, 20(44).