Conversion of Leather Industry Solid Waste to Organic Fertilizer by Vermicomposting: Use for Plant Growth

Abstract

The generation of leather industry solid waste is a matter of concern for its potential polluting ability. This study assessed vermicomposting of leather industry-generated lime flesh and shaving waste through a mix with cattle dung using Eisenia fetida earthworm, aiming at sustainable reuse in agriculture. The chromium content of shaving waste was optimized to under 2 mg/kg using hydrogen peroxide with potassium carbonate treatment. The lime flesh was treated with hydrochloric acid treatment. Treated shaving waste and lime flesh were mixed with cattle dung in a proportion of 1:1 and 2:1 in different vermicompost fields. After 30 days 40 Eisenia fetida were introduced in each field and vermicomposted for 90 days within a moisture of 50%. The number of earthworms increased in the 1:1 portion of vermicompost. The number of earthworms, pH, total organic carbon (TOC), total Kjeldahl nitrogen (TKN), carbon and nitrogen ratio (C: N), total potassium (TK) and total phosphorus (TP) readings was taken at 0, 30, 60 and 90 days respectively. Composting resulted in a significant reduction of pH, and TOC. A reduction in C: N ratio by approximately nine-fold and an increase in TKN and TP was observed. A slight reduction of TK was also observed. The results indicated that the earthworm Eisenia fetida has been able to convert the lime flesh and shaving waste into nutrient-enriched fertilizer products in the same proportion of waste and cow dung. The vermicompost was applied on the Napier grass plantation and the accumulation of heavy metal effect on plants was investigated for eco-friendly plant growth. The composts and plants’ different parts were analysed for heavy metals. It was found to be under the permissible limits recommended by WHO. The vermicompost enhanced the organic matter significantly and nutrients were improved for better crop yield.