Delayed methanogenesis and enhanced methane production in swine manure with Chlortetracycline residues: a biphasic effect on biogas efficiency

Biogas production from animal manure is a promising alternative to fossil fuels; however, antibiotic residues may affect process efficiency. This study evaluated the impact of chlortetracycline (CTC) on biogas production from swine manure by analysing CH4, CO2, H2S, and O2 at concentrations of 50, 100, and 500 mg/kg. CTC significantly reduced methane production during the early stages, with decreases of 70.22% on day 30 and 74.61% on day 43 at 500 mg/kg. However, methane production recovered over time, increasing by up to 25% from day 56 onwards. By day 69, methane production increased by 119.18% and 194.29% at 100 and 500 mg/kg, respectively. These results indicate a time-dependent effect of CTC, characterised by initial inhibition followed by recovery of methanogenic activity. The findings highlight the importance of considering temporal dynamics when assessing the impact of antibiotics on anaerobic digestion.