Biochar affects the dissipation of antibiotics and abundance of antibiotic resistance genes in pig manure

Manure from medicated livestock contains pharmaceutical antibiotics and antibiotic resistance genes (ARGs). Bioavailable antibiotics trigger further ARGs amplification during manure storage. It was tested whether biochar lowers the bioavailability of the antibiotics sulfamethazine (SMZ), ciprofloxacin (CIP), oxytetracycline (OTC) and florfenicol (FF) in manure and the amplification of sul1 and tet(W) ARGs. To that end, liquid pig manure was treated with 5% (w/w) pinecone biochar (BCP). Antibiotics dissipated during 30-d incubation in the order SMZ < OTC < CIP < FF. Added BCP further immobilized SMZ, OTC and CIP, while the effect was not significant for FF. Both sul1 and tet(W) ARGs copy numbers significantly increased by factors of 5.8 and 2.5, respectively, in OTC and SMZ spiked manure. The abundance of sul1 was significantly decreased in BCP amended manure, while the impact on tet(W) was less. Consequently, biochar is suitable for the management of antibiotics contaminated manure during storage.