Transforming leather waste into NPK fertilizers: A sustainable approach to boosting malabar spinach (Basella alba) growth

Abstract

The leather industry generates significant solid waste, posing serious environmental challenges. This study presents a sustainable approach to mitigating this issue by developing NPK-enriched organic fertilizers from chrome-tanned leather shaving wastes (CTLSWs), chicken and fish bone meal, and biochar derived from banana and orange peels. CTLSWs were treated with 10% NaOH for 24 h, successfully removing 99.98% of chromium. Two fertilizer formulations were developed: F-1, composed of dechromed collagen, chicken bone meal, and banana peel biochar in equal proportions, and F-2, containing dechromed collagen, fish bone meal, and orange peel biochar in a different ratio. Both formulations were characterized using SEM-EDS and FTIR analyses and evaluated for their impact on Malabar spinach (Basella alba) growth. Among the formulations, F-1 exhibited superior performance, increasing plant height by 23.43%, the number of leaves by 73.33%, leaf area by 67.54%, and branch numbers by 96.7% compared to the control. It also resulted in the highest dry matter accumulation in shoots (75.56%) and roots (9.82%), along with the best vigor index and germination rate. Although F-2 also enhanced plant growth, it was less effective than F-1. Both formulations improved nutrient uptake while keeping chromium levels in leaves within WHO safety limits. This study demonstrates an innovative and eco-friendly method for transforming hazardous leather waste into highly effective organic fertilizers. F-1 emerged as a promising alternative to chemical fertilizers, offering a sustainable solution for enhancing agricultural productivity while addressing environmental concerns.