Application of optimized hydrothermal, ozone and superalkali pretreatment techniques for qualitative biogas production from corn straw: A comparative assessment

Abstract

Pretreatment methods are prominently used to enhance methane production from any raw materials, with hydrolysis remaining a key bottleneck among such energy-environment balance pretreatment methodologies. This research explored the comparative potency of ozone (solid–liquid ratio-time-ozone dose), hydrothermal (solid–liquid ratio-time–temperature) and super-alkali (superalkali dose-time–temperature) pretreatment on corn straw by employing the required optimizing parameters. Response Surface Methodology (RSM) for each pretreatment processes were corroborated for batch and semi-continuous reactors. Comparing the three pretreatment methods, ozone pretreatment was leading to the utmost amount of methane production of 160.18 mL CH₄/g VS, which was 85.72% higher than that of the untreated group. The results demonstrated that the process leverages ozone’s strong oxidizing capacity to break down lignin, achieving a high delignification rate of 74.2% while retaining substantial fractions of cellulose and hemicellulose. No significant accumulation of phenol was observed following ozone pretreatment, with the system concentration remaining below the inhibitory threshold of 100 mg/L. In semi-continuous reactor, the tolerance to inhibitors and process stability were investigated simultaneously. The ozone-pretreated group exhibited a 7.8% increase in average biogas production, indicating microbial capability to degrade exogenously added inhibitory derivatives. An economic analysis was reviewed to strengthen the lucrative influence of ozone, ozone pretreatment of corn straw resulted in a 56.7% improvement in net profit. These findings indicate that ozone pretreatment can effectively recover resources from waste and improve the value conversion efficiency of waste.