Environmentally Friendly Carboxymethyl Cellulose Hydrogels Derived from Waste Paper and Sawdust as a Urea Release Agent

Abstract

This study investigates the development and application of cellulose hydrogel-based slow-release fertilizers derived from waste materials, specifically waste paper and sawdust, in cultivating water convolvulus. The slow-release fertilizers were created using carboxymethyl cellulose (CMC) derived from these waste sources with citric acid as a cross-linker, aiming to enhance nutrient efficiency and sustainable agricultural practices. The CMC hydrogels demonstrated high water swelling─approximately 10 times its dry weight, enhancing soil moisture holding levels across different soil types. Notably, the slow-release fertilizer derived from sawdust (HyU_CMC_SD) showed the highest urea absorption (330.8 ± 2.3 mg/g) and a high urea release rate in water and soil owing to its polymeric chain property. Cultivation trials over 25 days revealed that water convolvulus grown with the sawdust-derived slow-release fertilizer had the most extended stem growth, while the slow-release fertilizer from waste paper (HyU_CMC_P) provided gradual, more prolonged release, supporting consistent plant growth post-14 days of growing. Overall, slow-release fertilizers from the CMC hydrogels proved effective in slowing nutrient release, conserving soil moisture, and minimizing nutrient leaching. This research suggests that cellulose hydrogel-based slow-release fertilizers from waste materials offer a promising approach for sustainable and efficient agricultural production.