Enhancement of anaerobic digestion performance of rice straw by Tween 80: Effects, kinetics, and microbial mechanisms

Anaerobic digestion (AD) of lignocellulosic biomass such as rice straw (RS) was regarded as an effective way to promote renewable energy development. Optimizing the AD capability of RS has thus drawn considerable research interest. This study investigated the effects and underlying mechanisms of Tween 80 on methane production during the AD of RS. The results demonstrated that the addition of Tween 80 significantly enhanced methane yield and microbial activity. Specifically, methane production increased by 17.27 % compared to the control group, with a maximum methane content of 63.02 %. When combined with NaOH pretreatment, the performance was further improved. A cumulative methane yield of 210.71 mL/g TS (253.87 mL/g VS) was achieved, which corresponded to a 74.25 % increase over the control group. The maximum methane content reached 71.91 %. Mechanistic analysis revealed that Tween 80 improves the solubility of hydrophobic substances through micelle formation and reduces interfacial surface tension. These effects enhanced mass transfer and facilitated interactions between enzymes and substrates. Furthermore, Tween 80 facilitated exopolysaccharide (EPS) solubilization and enriched the hydrolytic biological community. The resulting increase in hydrolytic enzyme activity ultimately accelerated substrate transformation. Simultaneously, NaOH pretreatment provided sufficient substrate to further utilize the promoting effect of Tween 80. Overall, the synergistic effect of Tween 80 and NaOH pretreatment offered a promising strategy to improve the efficiency and stability of AD for lignocellulosic biomass. • A method for promoting methane production by adding Tween 80 was established. • Pretreatment of substrates with NaOH can further enhance the effect of Tween 80. • Tween 80 enhances EPS release / solubilization and improves microbial structure. • VFAs and methane yields improved via Tween 80 enhancement of hydrolase activity.