Landfill mining: A step forward to reducing CH4 emissions and enhancing CO2 sequestration from landfill

Landfill management is a major challenge for sustainable development in terms of climate change and resource scarcity. Landfill leachate contains high concentrations of nitrogen (N) and phosphorus (P), which cause eutrophication if discharged improperly. However, the nutrients can be recovered and reused as fertilizers for agriculture, contributing to resource recovery, circular economy, food security, and net zero emissions. Recent advances in landfill management have transformed landfills into resource recovery facilities that can produce nutrient-energy-material (NEM) products for applications through biological or physico-chemical process. Through a literature survey, this article reviews NEM recovery from landfills such as biogas production and composting. This work also discusses the benefits and challenges of NEM recovery for sustainability transition towards net zero emissions, while analyzes knowledge gaps and future research directions for landfill management and NEM recovery. It was conclusive from 193 articles published between 1993 and 2024 that landfill mining presents a promising solution for mitigating CH4 emissions and enhancing CO2 sequestration, both critical in reducing the overall greenhouse gas footprint of waste management. From landfill leachate and/or landfill gas, engineers can recover and recycle nutrients (for fertilizer), materials (for chemistry), and biogas (for electricity). Through landfill management, roadmaps towards decarbonization can be cost-effective and sustainable so that a maximum value of the waste can be extracted before it is discarded. Key findings reveal that CH4 emissions can be reduced by uncovering buried waste, while soil and residual organic material enhance CO2 sequestration through microbial activity. Additionally, this review highlights the economic and environmental benefits of material recovery from landfills, including metals and plastics. Overall, this work emphasizes landfill mining as a sustainable strategy for improving waste management practices, while contributing to climate change mitigation.