Alkaline thermal pretreatment at mild temperatures for biogas production from anaerobic digestion of antibiotic mycelial residue

Abstract

This paper aims at lowering the temperature for thermal pretreatment (TPT) of antibiotic mycelial residue (AMR) by alkali addition but without significantly worsening subsequent anaerobic digestion (AD) for biogas. Batch TPT and AD experiments were conducted in a bench-scale autoclave and several bench-scale anaerobic digesters, respectively. The results showed that the methane yield (<200ml·(gVS)−1) was visibly lower with lowering pretreatment temperature, compared to that (290ml·(gVS)−1) for TPT at the optimal temperature of 120°C, while it rebounded to 231ml·(gVS)−1 when proper amounts of alkali were employed (to adjust the pH of the AMR to 12) for TPT at 80°C. Further analysis indicated that low-temperature alkaline TPT was significantly less energy-consumption compared to only TPT, at cost of small amounts of alkali. It was more convenient and economical to implement AD of AMR in combination with alkaline TPT at mild temperatures for biogas.