Chapter Seven - Fate of bio-contaminants in organic wastes during composting and vermicomposting processes

Abstract

Organic wastes contaminated with potentially toxic bio-contaminants, e.g., antibiotics and heavy metals, pose serious environmental risks to soils and food chains. Therefore, strategies are needed to decrease or remove these contaminants during recycling of organic wastes. In this chapter, the fates of bio-contaminants in organic wastes are first introduced during thermophilic composting, vermicomposting, coupling composting, and vermicomposting processes. Specifically, composting process can remove antibiotics and markedly decrease the bioavailability of heavy metals, but it increases the total contents of heavy metals at the end of thermophilic composting. In contrast, vermicomposting process has a limited effect on removal of antibiotics but effectively removes a considerable content of heavy metals from the organic wastes. Intriguingly, coupling composting and vermicomposting processes are a new strategy for safe utilization of organic wastes by eliminating both antibiotics and heavy metals from the organic wastes. Next, advanced techniques of synchrotron-radiation-based spectromicroscopies, e.g., micro-X-ray fluorescence (μ-XRF) and μ-Fourier transform infrared (μ-FTIR), are introduced and combined to thermophilic composting and/or vermicomposting processes, for the purposes of identifying the binding characteristics of heavy metals and changes of functional structures in organic wastes. Taken together, this chapter provides a step toward understanding the fate of bio-contaminants in organic wastes during thermophilic composting and vermicomposting processes.