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Understanding Landfill Gas Behavior at Elevated Temperature Landfills
Citation:
Krause, M., N. Detwiler, W. Eades, D. Marro, A. Schwarber, AND T. Tolaymat. Understanding Landfill Gas Behavior at Elevated Temperature Landfills. WASTE MANAGEMENT. Elsevier Science Ltd, New York, NY, 165:83-93, (2023). https://doi.org/10.1016/j.wasman.2023.04.023
Impact/Purpose:
Over the previous decade, several landfills have exhibited unusual characteristics due to heat-generating (exothermic) reactions deep within the waste mass. Changes to landfill gas (LFG) composition indicate conditions are not suitable for typical landfill microbes. LFG data from several elevated temperature landfills (ETLFs) are compared and contrasted. The research can inform operators and regulators to understand the range of LFG observations from ETLFs undergoing unique subsurface reactions.
Description:
Landfill gas (LFG) extraction wellhead data were compared to understand the range of observations due to unique conditions at five elevated temperature landfills (ETLFs) in the US. Correlations of CH4 and CO2 show distinct compositional indicators for 1. typical operation, 2. subsurface exothermic reactions (SERs), 3. high moisture conditions and 4. air intrusion that can help operators and regulators diagnose conditions across gas extraction wells. Sometimes, decreased CH4 and increased CO2, H2, or CO content could be correlated to elevated LFG well temperatures. However, because LFG wellhead measurements are influenced by ambient air temperature, not all observations show correlation. In addition, one ETLF exhibited elevated CH4, likely from carbonation (CO2-consumption) of a steel slag which was used as an alternative daily cover (ADC). At the maximum gas well temperature, T = 82 °C/180 °F, CH4 and CO2 concentrations were 47% and 28%, respectively. At ETLFs A, C, and E, H2 > 50% were regularly observed in affected gas wells, higher than reported elsewhere. At the five ETLFs, maximum CO concentrations ranged from 1,400-16,000 ppmv. It is hypothesized that CO (ppmv)/H2 (%) < 100 suggest exothermic reactions of primarily industrial wastes producing hydrogen such as hydrolysis of aluminum wastes whereas CO/H2 > 100 reactions imply thermal degradation of primarily municipal solid waste (MSW). Co-disposal of industrial wastes and MSW and the use of potentially reactive ADCs should remain an important concern for landfill operators and regulators because of their potential long-term impacts to LFG quality.
