Researchers have developed a new type of engineered biochar that can deliver oxygen in a controlled and stable way, offering a promising solution for environmental remediation and sustainable water and soil management.
"Oxygen supply is critical for maintaining healthy ecosystems, but current materials often release oxygen too quickly or unpredictably," said the study's corresponding author. "Our work shows how biochar can be precisely designed to overcome these limitations and provide reliable oxygen delivery under real-world conditions."
Slow-release oxygen materials such as calcium peroxide are widely used to improve oxygen levels in aquaculture systems and contaminated soils. However, their performance is highly sensitive to environmental factors such as pH, ionic strength, and existing oxygen levels. Under unfavorable conditions, these materials can release oxygen too rapidly or inefficiently, limiting their effectiveness.
To address this challenge, the research team designed a series of modified biochars derived from rice husks, an abundant agricultural waste. By combining chemical modification and structural engineering, they created biochar materials capable of stabilizing calcium peroxide and controlling how oxygen is released over time.
The study compared three modification strategies: nitric acid oxidation, potassium hydroxide activation, and phosphate loading. Each approach altered the surface chemistry and pore structure of the biochar in different ways.
Among them, phosphate-modified biochar emerged as the most effective. It achieved a high loading of calcium peroxide while enabling a slow and sustained release of oxygen. This improved performance was linked to the formation of stable calcium–phosphorus bonds, which helped anchor the oxygen-releasing compound and regulate its behavior.
In contrast, biochar treated with nitric acid showed poor performance due to damage to its pore structure and increased acidity, which reduced its ability to hold calcium peroxide. Meanwhile, potassium hydroxide activation produced extremely high surface area biochar with rapid oxygen release, but less control over release stability.
The researchers also found that both chemical and physical properties of biochar play key roles in determining performance. Phosphorus content and pore size distribution were critical for loading capacity, while surface functional groups and material composition influenced how quickly oxygen was released.
Importantly, the phosphate-modified biochar demonstrated strong environmental adaptability. Its oxygen release remained stable across a range of pH levels, ionic strengths, and initial oxygen concentrations. This robustness makes it particularly suitable for complex natural environments where conditions can vary widely.
"Our findings highlight that the interaction between material structure and environmental conditions is dynamic," the authors explained. "By tuning biochar properties, we can design oxygen-releasing materials that perform reliably in diverse settings."
This research provides new insights into how biochar can be engineered as a functional carrier for controlled-release systems. Beyond oxygen delivery, the design principles identified in this study could be applied to other environmental technologies, including pollutant removal and nutrient management.
As global demand grows for sustainable and efficient environmental solutions, advanced biochar materials like these could play an important role in improving ecosystem health while making use of renewable biomass resources.
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Journal Reference: Zhang, W., Jiang, S., Wang, Y. et al. Chemical anchoring of CaO2 on phosphate-modified rice husk biochar for stabilized oxygen release. Biochar 8, 58 (2026).
https://doi.org/10.1007/s42773-026-00574-3
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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.
