A recent study by researchers at Pondicherry University in India has purportedly found that three species of earthworms are effective in removing up to 75 percent of heavy metals from domestic solid waste streams. Swati Pattnaik, et al., “Remediation of heavy metals from urban waste by vermicomposting using earthworms: Eudrilus eugeniae, Eisenia fetida and Perionyx excavates,” Int’l J. of Environment & Waste Management, September 2012. The study reports that earthworms can remove cadmium, copper, lead, manganese, and zinc from solid waste during processing, allowing for reuse of the waste products. The process of using worms to extract heavy metals from waste streams is known as “vermicomposting.”
According to the study, the worms do not become hazardous waste with the accumulated heavy metals in their systems, and the metals do not kill them. The researchers claim that the compost produced by vermicomposting could be used to grow human food without the risk of heavy metals accumulating in the crops. They suggest that more study is necessary to determine if such methods can be cost-effective on a large scale.