Biochar is increasingly viewed as a powerful tool for restoring degraded ecosystems, improving soil health, reducing greenhouse gas emissions, and immobilizing pollutants. But a new review published in Biochar highlights a key question for scientists, land managers, and policymakers: how much biochar should be used?
The answer, the authors report, is not "as much as possible." Instead, biochar works best within ecosystem-specific application windows. Too little may fail to restore soil function or control pollution, while too much can disturb soil pH, reduce microbial diversity, increase the bioavailability of some pollutants, and weaken restoration outcomes.
Led by Xiaoyong Bai and colleagues, the study integrated soil profile data, biogeochemical information, and microbiome-related evidence from six major ecosystems: agricultural land, grassland, forest, coastal wetlands, desert, and polar tundra. The team constructed a global biochar remediation threshold map and proposed practical application strategies tailored to different ecological settings.
"Our study shows that biochar should be treated as a precision restoration material, not a universal additive," said corresponding author Xiaoyong Bai. "The same application rate can produce very different outcomes in different ecosystems. Identifying the right threshold is essential for maximizing ecological benefits while avoiding new environmental risks."
The review identifies recommended application ranges of 5 to 30 tonnes per hectare for agricultural ecosystems, 5 to 40 tonnes per hectare for grasslands, 5 to 40 tonnes per hectare for forests, 10 to 50 tonnes per hectare for coastal wetlands, 10 to 40 tonnes per hectare for deserts, and 20 to 60 tonnes per hectare for polar tundra ecosystems.
Within these ranges, biochar can enhance ecological functions in several ways. The study reports that appropriate biochar use can increase soil water-holding capacity by about 10 to 14.3 percent, reduce greenhouse gas emissions by about 16.4 to 31.5 percent, lower heavy metal availability, increase soil organic matter, and support beneficial microbial activity. These benefits are especially important as land degradation, climate change, salinization, pollution, and extreme weather place growing pressure on ecosystems worldwide.
However, the authors caution that biochar thresholds are dynamic rather than fixed. The safe and effective range depends on the properties of the biochar, including raw material and pyrolysis temperature, as well as soil texture, soil organic matter, contamination status, climate conditions, and human management practices. For example, sandy soils, saline wetlands, freeze-thaw regions, and highly fertilized agricultural systems may require different application strategies even when they fall within the same broad ecosystem category.
To translate threshold science into practice, the authors propose a framework of "threshold identification, mechanism analysis, and targeted intervention." Recommended strategies include biochar plus fertilizer strip or spot application in farmland, staged low-dose application in grasslands, low-dose dispersal in forests, seasonal surface and localized application in coastal wetlands, rhizosphere-targeted application with water-saving management in deserts, and zoned medium- to low-dose management in polar regions.
The study also addresses a major gap in current biochar research. Many previous recommendations have focused on single ecosystems, especially farmland, or have provided broad dosage ranges without explaining why thresholds differ across regions. By linking material properties, ecological functions, and management strategies, the new review provides a quantitative basis for developing regional standards for biochar production and application.
"As biochar moves from research plots to large-scale ecological restoration, precision matters," Bai said. "Using the right amount in the right place can help biochar contribute to soil recovery, pollution control, climate mitigation, and sustainable land management."
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Journal Reference: Bai, X., Yuan, X., Li, X. et al. How much biochar should be used in global ecological restoration?. Biochar 8, 100 (2026).
https://doi.org/10.1007/s42773-026-00603-1
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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.
