Environmental Fate of Antibiotics and Resistance Genes in Livestock Waste and Digestate from Biogas Plants

Huge amounts of antibiotics are currently being used in both human and veterinary medicine. Moreover, most are recalcitrant to biodegradation and can persist in the environment. In fact these compounds have been increasingly found as micro-contaminants in natural ecosystems and cause particular concern because of the development of multi-resistant bacteria, posing serious risks for human and animal health. In particular, the antibiotics used in livestock farms can persist in manure, causing environmental contamination if used as a biofertilizer. However, farm manure can also be a feed for biogas reactors and the digested effluent (digestate) used as fertilizer or soil improver. The fact that the latter can still contain antibiotic residues and possibly antibiotic resistance genes still remains to be clarified.