Resource Mining for a Bioreactor Landfill

Background: A new generation of the sustainable landfill is designed to achieve sustainable Municipal Solid Waste (MSW) management. It is hybrid anaerobic/aerobic biodegradation landfill followed by landfill mining. However, there is limited information on landfill mining, especially the criteria and process for the practitioner to determine the end of the landfill biodegradation to commence landfill mining. Objective: Hence the overall objective of this research was to develop a comprehensive resource mining plan for bioreactor landfills. Method: When waste decomposition becomes slower or stopped, the landfill can be mined to recover resources and utilize the recovered space. The amount of the gas generated, landfill temperature and landfill settlement are indirect measures of landfill activity. Also, the concentration of cellulose (C), hemicelluloses (H), and lignin (L) can describe the biodegradable fractions of waste. Hence the biodegradation in landfills can be monitored by recording the change in methane production, temperature, settlement and the (C+H)/L ratio of waste. Once methane recovery is minimal, landfill reaches a maximum settlement and, ambient temperature plus the (C+H)/L value reaches a stable value of 0.25 indicating end of biodegradation. At this point landfill resources including compost material, non-recoverable waste, and recyclables such as plastics, metal and glass can be mined and recovered. Compost and recyclables can be sold at market value and the non-recovered waste with high energy content can be used as refuse-derived fuel. Once the landfill has been mined space can be reused thus eliminating the need to allocate valuable land for new landfills. Result: The landfill mining detailed in this manuscript utilizes principles from single stream type recycling facilities to ensure feasibility. The first landfill will be excavated and screened to separate the biodegraded soil and compost fraction from the recyclables. Then the screened recyclable materials are transported for further processing in a single stream type separation facility where they will be separated, bundled and sold. Conclusion: A cost calculation was performed for the resource mining of Calgary Biocell and if the mined resources are sold at market values, then the mining of Calgary Biocell would generate approximately $4M.