The Journal of Agriculture and Food Research recently published a study by Cheng Yi, Zhi Zhou, Wei Luo, and their research team at Hunan Agricultural University exploring a sustainable solution to a long-standing challenge in tea cultivation. Tea is one of the most popular beverages on the planet, but the plants are known to naturally soak up high levels of fluoride from the soil. While small amounts of fluoride are fine, excessive intake is linked to health issues like skeletal fluorosis and neurological concerns. This research introduces a specialized, calcium-modified biochar made from tea waste that significantly lowers the fluoride content in the final product while actually improving the environment where the tea grows.

The researchers focused on creating a modified biochar using spent dark tea residue, turning a waste product into a powerful 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. By doping this biochar with 3 percent calcium oxide and treating it with a potassium sulfate wash, they developed a material that effectively locks fluoride away. When applied to soil in controlled experiments, this specific version of biochar reduced the fluoride content in young tea leaves by 48.6 percent. This is a major improvement over standard charcoalCharcoal is a black, brittle, and porous material produced by heating wood or other organic substances in a low-oxygen environment. It is primarily used as a fuel source for cooking and heating.   More or bamboo-based additives used in previous studies. The modified biochar achieves these results through several clever mechanisms, most notably by transforming water-soluble fluoride into stable, insoluble solids that the plant cannot easily absorb.

Beyond simply trapping fluoride in the soil, the modified biochar changes how the tea plant handles the minerals it does take in. The study found that the presence of extra calcium acts as a biological roadblock. Instead of traveling all the way to the leaves, which are the parts humans eventually consume, a significant portion of the fluoride is sequestered in the stems of the plant. This internal redistribution ensures that the most economically and nutritionally important parts of the plant remain safer for consumption. Furthermore, the biochar helps the plant stay healthy and resilient by boosting the availability of nitrogen, phosphorus, and potassium in the rhizosphere, the thin layer of soil directly surrounding the roots.

The environmental benefits of this treatment extend to the microscopic level. The application of the modified biochar was found to restructure the bacterial and fungal communities in the soil. It specifically encouraged the growth of beneficial bacteria like Pseudomonas and Bradyrhizobium, which are known for their ability to tolerate fluoride and assist in nitrogen fixationNitrogen is a crucial nutrient for plant growth, but plants can’t directly absorb it from the air. Nitrogen fixation is a process where certain bacteria convert atmospheric nitrogen into a form that plants can use. Biochar can provide a home for these nitrogen-fixing bacteria, enhancing More. The researchers also observed an increase in certain fungi that help fix fluoride in the soil, preventing it from leachingLeaching is the process where nutrients are dissolved and carried away from the soil by water. This can lead to nutrient depletion and environmental pollution. Biochar can help reduce leaching by improving nutrient retention in the soil.   More away or being taken up by the roots. This shift creates a more robust and functional soil ecosystem that supports sustainable farming.

By using tea waste to protect future tea harvests, this research promotes a circular agricultural model that reduces carbon emissions and waste. The study proves that targeted soil amendments can address food safety concerns while simultaneously rehabilitating the land. Although these results were observed in short-term trials, they provide a strong mechanistic foundation for using modified biochar in commercial tea gardens. This approach offers a practical way for the tea industry to meet strict international safety standards and protect public health without relying on harsh chemicals or expensive, energy-intensive remediation techniques.

Source: Yi, C., Zhou, C., Mo, Y., Peng, X., Chen, L., Xin, S., Liu, Y., Xie, Y., Zhou, Z., & Luo, W. (2026). Study on the mechanism of modified biochar in reducing fluoride content in tea leaves and improving soil environment. Journal of Agriculture and Food Research, 27, 102769.