Impact of corn stover particle size and C/N ratio on reactor performance in solid-state anaerobic co-digestion with dairy manure

Abstract

ABSTRACTGreen energy generation from agricultural waste has the potential to minimize dependency on fossil and reduce the resultant environmental impact of this fuel provided anaerobic reactor performance is optimized. Hence, the interactive impact of carbon to nitrogen (C/N) ratio, particle size, and co-digestion of dairy manure (DM) and corn stover (CS) on solid-state anaerobic digester (SSAD) performance was investigated with four treatments (DMCS24S, DMCS24L, DMCS28L, and DMCS32L) in this solid-state study. Novel scanning electron microscope (SEM) image analysis utilized to describe the corn stover using ImageJ indicated that corn stover of particle size 0.18–0.42 mm had lower rough surface texture relative to the 0.42–0.84 mm size. This observation not only influenced the ingestate degradation, the bioconversion rate was negatively affected by 0.18–0.42 mm particle size of corn stover. Notably, increase in C/N ratio led to decrease in total ammonia nitrogen (TAN) and alkalinity concentration (Alk), hence, treatments with the lowest C/N ratio had better reactor performance in terms of suitable process parameters such as Alk, pH, ORP, and TAN. Furthermore, DMCS24L treatment had the highest methane yield (106 mL/g VS) and net methane energy (2.92 MJ/kg). Interestingly, modified Gompertz model gave the best kinetic description of the methane production. This SSAD mesophilic study suggests that corn stover, with particle size of 0.42–0.84 mm, co-digested with dairy manure under a C/N ratio of 24 has the potential to enhance methane yield and optimize reactor performance.Implications: The utilization of agricultural waste for bioenergy generation through solid-state anaerobic digestion could be enhanced through the interactive impact of substrate particle size, carbon-to-nitrogen (C/N) ratio and co-digestion, which has not been previously studied. These ternary factors significantly improved reactor performance and enhanced methane yield when corn stover of 0.42–0.84 mm particle size was co-digested with dairy manure to achieve a C/N ratio of 24.