Collagen hydrolyzed extract derived from leather waste as a multifunctional additive for the preparation of granular fertilizer

Abstract

Effective treatment and high-valued utilization of chrome leather scraps have always been desired by all tanneries, which is of great significance for green and sustainable development of leather industry. In this paper, we first devised a green and effective approach to obtain collagen hydrolyzed extract (CHE) from chrome leather scraps, and then the obtained CHE was used in the granulation of pastoral soil to prepare CHE-Soil granular fertilizer. The results indicated that chrome leather scraps were effectively dechromed with sodium oxalate and then hydrolyzed by a high-pressure hydrothermal method without any chemical to obtain high-purity CHE. When the 4.5 wt%∼12.5 wt% CHE solution was introduced into the granulation process, the granulation rate of pastoral soil was up to 89.8%∼95.6%. However, the effective granulation rate was decreased due to the increase in large granule size (>5 mm). CHE-Soil granular fertilizer prepared by adding more CHE exhibited better surface roundness and more excellent crush resistance. Moreover, this type of granular fertilizer possessed excellent water retention and slow-released nutrient properties. Pine leaf peony cultivation experiments further showed that the presence of CHE-Soil granular fertilizer rapidly promoted plant growth and effectively increased the harvest of plants. This study indicated that CHE obtained from chrome leather scraps could be effectively used as a nutritious additive with adhesiveness to prepare the granular fertilizer for plant growth, which provides a novel idea for designing valorization methods of leather waste.