Chapter Fifteen - Bioconversion of hazardous organic wastes using invertebrates

Abstract

Bioconversion of solid organic wastes into value-added products is a viable and low-cost option for waste management. However, solid organic wastes containing contaminants such as biosolids, animal manures, food wastes, and crop residues are a challenge for the viability of the biological decomposition process and the environmental safety of the resultant compost. Currently, composting, anaerobic digestion, and vermicomposting are the most common techniques for treating potentially hazardous organic wastes. Recently, insects larvae are emerging as a viable strategy for decomposing hazardous organic residues, including plastic wastes. In this chapter, we examine and compare the effects of vermicomposting and insect-based bioconversion on removing heavy metals, legacy and emerging organic pollutants, and pathogens, including antibiotic-resistant genes. Although there is a huge body of literature reporting how vermicomposting alters metal speciation and reduces pathogens, pharmaceuticals, and other organic pollutants, the mechanisms underpinning such beneficial effects are still speculative, and more research is needed to explore the toxicity of these pollutants (and derived metabolites) on the biological processes of vermicomposting. The final scope of using vermicomposting and insect-based bioconversion as bioeconomy options in managing hazardous organic wastes is the production of pollutant-free or nontoxic composts. To this, the inclusion of biochar (carbonaceous material generated by pyrolysis of biomass) in these biotransformation processes accelerates the organic matter decomposition and improves the quality of the resultant carbonaceous-rich composts as fertilizers. Both biotechnologies are considered nature-based solutions for alleviating at least three main soil threats: soil organic matter decline, contamination, and loss of soil biodiversity.