Evaluation of the Temperature Range for Biological Activity in Landfills Experiencing Elevated Temperatures

Abstract

There have been reports of municipal solid waste landfills with waste and gas wellhead temperatures of at least 80−100 °C, which is in excess of temperatures reported at typical landfills. Landfills experiencing heat accumulation over a broad area present a number of challenges involving leachate and gas quality and quantity, and the associated collection infrastructure. The objectives of this research were to evaluate the impact of temperature on methanogenesis and fermentation in landfills, and to evaluate the extent to which microbial populations acclimate when perturbed to either lower or higher temperatures relative to their in situ temperature. Samples excavated from two landfills exhibiting elevated temperatures were utilized as inocula for small-and reactor-scale experiments. The optimum temperature for methane generation in the thermophilic range was 47.5−57.5 °C, with yields reduced by ∼37 and 75% at 62.5 and 67.5 °C, respectively. While microbial populations did not acclimate above 67.5 °C, methanogenic activity resumed when waste was cooled. 16S rRNA sequencing revealed that Methanothermobacter likely plays a key role in facilitating methane production in landfills operating in the thermophilic range and that microbial community diversity decreased at higher incubation temperatures. There was evidence that fermentation occurs up to 77.5 °C, well above the upper limit for methanogens measured in this study. Model simulations predict that fermentation reactions contribute a ∼3−10 °C rise in waste temperature.

Landfill Emissions of Methane Inferred from Unmanned Aerial Vehicle and Mobile Ground Measurements

“…Much attention has recently been devoted to Elevated Temperature Landfills (ETLFs), in which sub-surface temperatures rise beyond normal range due to biological and chemical reactions among waste products and the trapping of heat by liquids [14,15]. While this may suppress the methane content of landfill gas by exceeding the optimal range of temperatures for methane generation [16], physical deterioration of the gas collection system due to elevated temperatures may lead to fugitive emissions of methane.…”

Quasi-Mechanistic 3D Finite Element Model Predicts Temperatures in a U.S. Landfill

“…From 2012 to 2016, temperatures on both the northern and southern parts of the slices (Figure 4a) increased. An elevated temperature zone (ETZ) was defined as a waste temperature >70 °C based on Schupp et al 31 who showed that methane yields were reduced by 75% at 67.5 °C and by ∼90% at 72.5 °C in refuse samples excavated from a landfill that was exhibiting elevated temperatures. An ETZ formed in the southern part of the landfill, where the maximum temperature is predicted to reach 100 °C (Figure 4b).…”

Effect of increased temperature and leachate recirculation on biogas production and settlement of municipal solid waste

“…The results show that the CH 4 /CO 2 ratios start from 0.06, 0.2 and 0.5 for each test, respectively, and then approach the stable range after around 40, 7 and 7 days, respectively. Temperatures higher than the optimum temperature, up to 55°C and 57.5°C, according to Benson (2017) and Schupp et al (2021), respectively, have been shown to reduce the primary gas ratio due to methanogenic microbial community diminishing. Based on the primary gas ratio, it can be concluded that all three sets of tests were under stable methanogenic conditions, with the only difference being the onset time and rate of reaching stable methane production.…”