Researchers at the Universidade Federal de Lavras in Brazil have investigated the conversion of Nile tilapia (Oreochromis niloticus) scales into nutrient-rich biochar to serve as a sustainable phosphorus source for agriculture. Published in 2026, the study analyzed the physicochemical transformations of fish scales under slow pyrolysis at temperatures ranging from 300°C to 600°C. The analytical results confirm that thermal processing effectively transforms raw aquaculture waste into a stabilized mineral matrix. By characterizing the resulting biochars through elemental analysis and scanning electron microscopy, the team established a clear link between processing temperatures and the efficiency of nutrient delivery in wheat cultivation.

The primary challenge addressed by this research is the environmental mismanagement of aquaculture residues and the inefficiency of conventional phosphate fertilizers. Fish scales are a significant byproduct of the Brazilian fishing industry, yet they are frequently discarded, leading to waste disposal issues despite their high phosphorus and calcium content. Furthermore, traditional highly soluble phosphorus fertilizers are prone to rapid soil fixation or leaching, which reduces nutrient use efficiencyNutrient use efficiency refers to how effectively plants can take up and utilize nutrients from the soil. Biochar can improve nutrient use efficiency by enhancing nutrient availability and retention in the soil.   More and necessitates frequent applications. Developing a method to stabilize these organic residues into a format that releases nutrients in synchronization with plant demand is essential for advancing circular economy goals in the fertilizer sector.

The researchers implemented a solution by engineering biochars specifically designed for controlled phosphorus elution. Using slow pyrolysis, the team stabilized the hydroxyapatite structure found in the fish scales, with higher temperatures (600°C) yielding a more porous and mineral-dense material. They utilized the Peppas-Sahlin and Korsmeyer-Peppas mathematical models to analyze the kinetics of phosphorus release, ensuring the material functioned as a legitimate slow-release fertilizer. This engineering approach allowed for a “diffusion-controlled” mechanism, where the phosphorus is released gradually into the soil rather than in a single, wasteful burst characteristic of raw biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More.

The outcomes of the study indicate that fish scale biochar produced at 600°C maximizes phosphorus availability, with approximately 84% of the total phosphorus content remaining accessible to plants. In greenhouse trials using wheat, the biochar treatments significantly improved plant growth parameters compared to untreated soil, demonstrating its efficacy as a functional replacement for mineral phosphorus. The study concludes that increasing pyrolysis temperatures enhances the phosphorus-to-carbon ratio and provides a consistent nutrient supply throughout the crop cycle. This research provides a scalable framework for turning fish processing waste into high-value, sustainable agricultural inputs.

Source: Vitor, G. S., Oliveira, J. E., Paiva, A. M., Boaventura, T. P., & Melo, L. C. A. (2026). Effect of pyrolysis temperature on phosphorus release from fish scale biochar in wheat crop. Chemical Engineering & Technology, 49(e70181).