Effects of organic loading rate and pretreatments on digestion performance of corn stover and chicken manure in completely stirred tank reactor (CSTR)

Abstract

The performance, system stability, and microbial community response in anaerobic co-digestion (AcoD) of corn stover (CS) and chicken manure (CM) were investigated by running completely stirred tank reactor (CSTR) under controlled organic loading rate (OLR). Prior to anaerobic digestion (AD), potassium hydroxide (KOH) or liquid fraction of digestate (LFD) was applied to pretreat CS, respectively. The results showed that the daily biogas production (DBP) in co-digestion showed a gradual increasing trend with an increase in the OLR from 65 g TS·L−1 to 100 g TS·L−1. The daily methane production per g volatile solids (DMP-VS) in co-digestion increased by 23.0%–27.1%, 18.7%–18.8%, and 17.5%–18.0% at the OLRs of 65, 80, and 100 g TS·L−1, respectively, upon pretreatment with KOH or LFD, as compared to that in co-digestion CSTR without any pretreatment. In addition, all co-digestion CSTRs were operated in stable state. Approximately half of the total carbon in the substrates was recovered in the form of a biogas product, with the carbon mass balance being impacted by the OLR as well as pretreatment. The diversity as well as function of the microbial community varied in response to different OLRs and pretreatment methods. The majority of bacterial genera were strongly correlated with operational parameters. The study indicates that management of OLR and selection of proper pretreatment method could enhance the efficiency and productivity of CS and CM co-digestion in CSTR.