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

## TL;DR

This paper introduces a new type of fertilizer made from chitosan and liquid digestate that can slowly release potassium and phosphorus to support plant growth.

## Contribution

The novel contribution is the development of cryo-structured chitosan sponges with controlled release properties for agricultural nutrients.

## Key findings

- Cryo-structured sponges were successfully created using chitosan and liquid digestate.
- The sponges showed controlled release properties for potassium and phosphorus.
- Characterization techniques confirmed the incorporation of liquid digestate into the sponges.

## Abstract

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.