Low-temperature anaerobic co-digestion of swine carcass and swine manure: Impact of high swine carcass loading rate

Proper disposal of mortalities during emergency animal disease outbreaks is critical for livestock operations. To date, carcass disposal by biosecure anaerobic digestion (AD) is limited. Therefore, the objective of this study was to investigate the influence of co-digestion of swine carcass (SC) and swine manure (SM) at higher carcass loading rates (CLRs), i.e., 117, 233, and 467 kgcarcass m-3manure (corresponding to an organic loading rate of 3 g COD L-1 d-1), on the performance and stability of psychrophilic AD in sequencing batch reactors (PADSBRs) at 24.5°C ± 0.5°C. Higher CLR rates were considered primarily to simulate the high mortality rates associated with emergency disease outbreaks. Experimental results indicated that accumulation of propionic acid was observed even at CLR of 117 kgcarcass m-3manure. The slow degradation of the lipid and fat content in SC probably inhibited the AD process, particularly at higher CLR. Inhibition was chiefly due to increasing CLR rather than ammonia concentration. As dilution resulted in possible reduction of accumulated acetic and propionic acids in the PADSBRs at the end of the study, further investigation is underway to establish efficient operating strategies for optimal co-digestion of SC.