Evaluation and modelling of methane production from corn stover pretreated with various physicochemical techniques

Lignocellulosic by-products from agricultural crops represent an important raw material for anaerobic digestion and clean renewable, which is a key component of the circular economy. Lignocellulose is recalcitrant to biodegradation and pretreatments are required to increase methane yield during anaerobic digestion. In this work, the efficacy of different physicochemical pretreatments was compared using corn stover biomass as substrate. Anaerobic digestion of untreated and pretreated corn stover was performed in batch mode at mesophilic temperature (38°C) and organic matter solubilization of pretreated substrates was also investigated. The highest organic matter solubilization occurred in autoclave pretreatment (soluble chemical oxygen demand = 5630 ± 42 mg O₂ L^-1). However, the highest methane yield was obtained using alkaline pretreatment (367 ± 35 mL CH₄ g^-1 VS_added). Alkaline pretreatment increased methane yield by 43.3% compared to untreated control (256 ± 15 mL CH₄ g^-1 VS_added). Two mathematical models (i.e. first-order kinetics and transfer function) were utilized to fit the experimental data with the aim of assessing anaerobic biodegradation and to obtain the kinetic constants in all cases studied. Both models adequately fit the experimental results. The kinetic constant, k, of the first-order model increased by 92.8% when stover was pretreated with sulphuric acid compared with control. The transfer function model revealed that the maximum methane production rate, R_m, was obtained for the sulphuric acid treatment, which was 63.5% higher compared to control.