Effects of multiple antibiotics on greenhouse gas and ammonia emissions during swine manure composting.

Antibiotics are commonly used in intensive farming, leading to multiple antibiotic residue in livestock waste. However, the effects of multiple antibiotics on the emissions of greenhouse gas and ammonia remain indistinct. This paper selects sulfamethoxazole and norfloxacin to represent two different types of antibiotics to explore their effects on gaseous emissions. Four treatments including CK (control), SMZ (spiked with 5 mg kg-1 DW sulfamethoxazole), NOR (spiked with 5 mg kg-1 DW norfloxacin), and SN (spiked with 5 mg kg-1 DW sulfamethoxazole and 5 mg kg-1 DW norfloxacin) were composted for 65 days. Coexistence of sulfamethoxazole and norfloxacin facilitated the biodegradation of organic carbon, and significantly (p < 0.05) increased the cumulative CO2 emission by 31.9%. The cumulative CH4 emissions were decreased by 6.19%, 23.7%, and 27.6% for SMZ, NOR, and SN, respectively. The total NH3 volatilization in SMZ and NOR rose to 1020 and 1190 mg kg-1 DW, respectively. The individual existence of sulfamethoxazole significantly (p < 0.05) ascended the N2O emission rate in the first 7 days due to the increase of NO2--N content. In addition, coexistence of sulfamethoxazole and norfloxacin notably dropped the total greenhouse gas emission (subtracting CO2) by 15.5%.