Resilient and Sustainable Biogeochemical Landfill Cover for Mitigating Fugitive Gas Emissions

Municipal solid waste (MSW) landfills are a significant source of greenhouse gas emissions, contributing to global climate change. Conventional landfill gas (LFG) management systems, such as gas collection and soil cover (SC) systems, are limited in their ability to fully capture and mitigate these emissions. This research explores the development of an innovative biogeochemical cover (BGCC) system designed to enhance the mitigation of methane (CH₄) and carbon dioxide (CO₂) through microbial oxidation and mineral carbonation processes, respectively. The proposed BGCC system integrates biochar-based biocovers for CH₄ oxidation and alkaline industrial byproducts for CO₂ sequestration, offering a more comprehensive approach to gas mitigation compared to traditional SC systems. The study initially focused on near-field-scale testing of a BGCC system incorporating pinewood biochar based biocover and basic oxygen furnace (BOF) slag, comparing it to conventional SC systems. The BGCC system demonstrated higher CH₄ removal efficiency (74.7–79.7%) at moderate influx rates (23.9-25.5 g CH₄/m²·day) and achieved complete H₂S removal, while also sequestering CO₂ through mineral carbonation. However, CO₂ breakthrough occurred after 156 days of continuous exposure, likely due to desiccation of the BOF slag layer. Microbial analysis revealed that Type I methanotrophs, such as Methylobacter, dominated the BGCC systems, driving CH₄ oxidation. To further enhance the BGCC system’s performance and reduce reliance on BOF slag and pinewood biochar, alternative materials were investigated. Batch experiments identified cement kiln dust (CKD) as a promising replacement for BOF slag due to its higher CO₂ sequestration capacity (225 mg/g compared to 98.1 mg/g for BOF slag). Similarly, rice husk (RH) biochar exhibited the highest CH₄ oxidation potential (6595.4 µg CH₄/g) among six biochars produced from different feedstocks, including pinewood biochar. Following the evaluation of these alternative materials, a modified BGCC system incorporating RH biochar and CKD (BGCC-RHCKD) was developed and compared to the previously developed BGCC-PWBOF (pinewood biochar and BOF slag) and SC systems. The BGCC-RHCKD system achieved 100% CO₂ removal efficiency without breakthrough, outperforming BGCC-PWBOF, while maintaining CH₄ removal efficiency comparable to that of the SC system at moderate influx rates (20.77-22.80 g CH₄/m²·day) during Phase 1. Microbial analysis revealed that Type I methanotrophs, such as Methylobacter luteus, dominated the BGCC systems (BGCC-RHCKD and BGCC-PWBOF), driving CH₄ oxidation. Overall, this study demonstrates that BGCC systems offer a comprehensive solution for LFG management by effectively mitigating CH₄, CO₂, and H₂S emissions while promoting the circular economy through the valorization of waste materials. The adaptability of BGCC systems to variable gas compositions and influx rates, coupled with their dual capability for emission reduction and resource recovery, positions them as a sustainable and resilient alternative to conventional LFG management practices.