Cryo-Structured Chitosan Sponges with Controlled Release Properties for Liquid Digestate as Potential Agricultural Fertilizers

Phosphorus and potassium are two of the most essential macronutrients that often work together to support plant health and productivity. If one of these elements is deficient, it can lead to reduced plant growth, low yields, and poorer crop quality. For this reason, fertilizers contain these nutrients to replenish soils that have been depleted over time. As a sustainable approach, this study proposes new cryo-structures based on chitosan and liquid digestate with controlled release properties for potassium and phosphorus. For this purpose, commercial chitosan (a biopolymer extracted from marine waste) was used along with a liquid digestate, obtained through anaerobic digestion, to develop cryo-structured sponges. The incorporation of liquid digestate in the cryo-structured sponges was confirmed using different characterization techniques (FTIR, TGA/DTG, SEM, and EDX), while the release mechanism for phosphorus and potassium was investigated using ICP-OES spectroscopy.