Optimum thermal treatment for removing antibiotic resistance genes and retaining nutrients in poultry broiler manure

Poultry broiler manure is a reservoir of antibiotic resistance genes (ARGs), antibiotics, organic carbon, and plant nutrients. However, its direct application leads to spread of ARGs in agricultural fields, causing public concerns. It is thus crucial to identify optimum heating conditions that remove ARGs while retaining nutrients. This study examined the effects of heating temperatures (100–500 °C) and durations (30, 120 and 240 min) on the removals of ARGs and antibiotics from poultry broiler manure and nutrient retention. The results showed that the poultry broiler manure contained a total of 211 ARG subtypes, which were susceptible to temperature. The contents of ARGs and antibiotics decreased with increasing temperature. The temperature had a significant effect on the loss of available phosphorus (r = −0.893, P <0.01), while other nutrients had no significant loss. The results showed that the heat treatment at 110 °C for 240 min maximized the removals of ARGs while the loss of nutrients was minimized. Under these optimum conditions, all ARGs and antibiotics (e.g., oxytetracycline, tetracycline, doxycycline, tilmicosin, tylosin, sulfamethazine, and sulfadiazine) were removed while 91.98 % of total carbon, 99.89 % of total nitrogen, 92.38 % of total phosphorus, 50.10 % of available phosphorus, 99.96 % of total potassium, and 95.02 % available potassium were preserved. These findings suggest that heat treatment at 110 °C for 240 min could be an effective and affordable approach to safe use of poultry broiler manure.