Bioconversion of agro-industrial effluent sludge into bio-fertilisers: A sustainable waste management approach

Abstract

The rapid growth of agro-industrial activities has led to the generation of substantial quantities of effluent sludge, posing serious environmental and waste management concerns. Despite these challenges, agro-industrial sludge contains significant amounts of organic matter and plant nutrients, making it a valuable resource for agricultural applications when properly treated. This review explores the conversion of agro-industrial effluent sludge into biofertilisers as a sustainable strategy for waste valorisation and nutrient recycling within a circular bioeconomy framework. It discusses the characteristics of sludge, associated environmental risks and the treatment processes required to ensure safe agricultural use. Major bioconversion approaches, including composting, vermicomposting, microbial inoculation, anaerobic digestion and thermochemical methods, are critically evaluated. The review also highlights the role of beneficial microorganisms in nutrient transformation and recovery, as well as emerging technologies such as biochar-based fertilisers, electrochemical nutrient recovery systems and integrated sludge biorefineries. Findings from laboratory and field studies demonstrate that sludge-derived biofertilisers can enhance soil fertility, improve microbial activity, increase nutrient availability and support crop productivity while reducing dependence on synthetic fertilisers. However, issues related to heavy metals, organic contaminants, pathogen removal, product quality and regulatory compliance remain important challenges. Overall, the bioconversion of agro-industrial sludge into biofertilisers offers a promising pathway for sustainable waste management, resource recovery, environmental protection and resilient agricultural development.