Introduction of acid-neutralizing layer to facilitate the stabilization of municipal solid waste landfill

[Display omitted] •Acid-neutralizing layer mitigated the acid accumulation of landfill.•The stabilization process of landfill was enhanced by acid-neutralizing layer.•The landfill gas production increased by 18.3% and CH4 concentration was promoted.•The microbial community richness and the abundance of methanogens were promoted. Rapid stabilization is important for landfill operation and beneficial for treatment capacity recovery, biogas production, and pollution control. Acidification of municipal solid waste (MSW) landfill hinders the degradation of MSW. In this study, a leachate-recirculated landfill bioreactor with acid-neutralizing layer (reactor BL) and a control landfill bioreactor without the acid-neutralizing layer (CL) were operated for 509 days. The pH of the landfill was increased by the acid-neutralizing layer. The landfill gas production volume increased by 18.3 % in reactor BL compared with CL during the study period, and the CH4 concentration was also increased. A greater MSW mass reduction was observed in reactor BL than in CL. Microbial community analysis demonstrated that the presence of the acid-neutralizing layer promoted the abundance of methanogens. Based on these observations, it is believed that application of the acid-neutralizing layer accelerated the stabilization by mitigating the acidification of landfill, which promote the abundance of methanogens and enhance the MSW degradation. These results help to understand the influencing mechanism of acid-neutralizing layer on the landfill stabilization, and provide a new approach for the practical landfill to achieve fast stabilization.