Comparison of the Reactor Performance of Alkaline-Pretreated Corn Stover Co-digested with Dairy Manure Under Solid-State

Abstract

Solid-state anaerobic digestion is a promising path to optimize green energy generation from waste management. This mesophilic study investigated the performance of sodium hydroxide (4%NaOH), ammonium hydroxide (2%NH4OH, and 4%NH4OH), and calcium hydroxide (8%Ca(OH)2) pretreated corn stover (Cs) co-digested with dairy manure (Dm) to achieve 4%NaCsDm, 2%AqCsDm, 4%AqCsDm, and 8%CaCsDm treatments. Results showed that 8%CaCsDm had shortened detention time (79 days) and increased methane yield (178 L/kg VS) in comparison with other treatments. In addition, propionic acid concentration in treatment 4%NaCsDm was elevated beyond a safe threshold (> 0.9 g/L) for methanogens, which is unlike the significant bioconversion that occurred for other treatments. Though, free ammonia concentration for 2%AqCsDm and 4%AqCsDm pre-digestates were within the safe limit (< 53 mg/L) relative to other treatments, 8%CaCsDm sufficiently reduced the initial inhibitory concentration to a safe threshold at the cessation of the experiment. Additionally, 8%CaCsDm treatment had the highest VFA bioconversion rate (80%). Therefore, this study demonstrated that 8%CaCsDm treatment could effectively improve reactor performance in solid-state anaerobic co-digestion.