Abstract
Methane emissions from municipal solid waste (MSW) landfills and waste management comprise 15 – 18% of the global anthropogenic methane emissions budget (Krautwurst et al., 2017). Although landfills are strictly regulated in California and required to capture emitting methane gas, the gas control systems designed to capture excess gas require constant maintenance and often leak. The geography, geology, microclimate, and management practices vary between facilities. Understanding how ambient temperature, precipitation, and pressure influence fugitive methane emissions is essential because it can help landfill operators maintain and reduce excess emissions by understanding the facility's local area.
This project reviews previous Landfill Methane Rule (LMR) annual reports in calendar years 2012 – 2020 of two landfill facilities located in different microclimates within Northern California. The present work focuses on how environmental variables affect methane emissions from landfills. The following hypotheses will be tested: 1) methane emissions exhibit a seasonal pattern, 2) moisture influences methane emissions, 3) California Air Resources Board (CARB) and LMR’s measurement techniques produce similar methane emission values. Precipitation, temperature, and atmospheric pressure data were collected from the National Oceanic and Atmospheric Administration (NOAA) stations closest to the facility. CARB staff collect data in 2020 from landfills using a Toxic Vapor Analyzer 2020 (TVA2020), soil meter, Garmin GPS receiver, anemometer, and barometer to collect methane, soil moisture, soil temperature, the GPS location of each wellhead sampled, ambient temperature, and atmospheric pressure. All variables were compared graphically and with statistical analysis to determine the influence of environmental parameters on methane emissions. Data collected by CARB staff is compared to LMR reports using ArcGIS. Results from the two methods did not produce similar spatial patterns or magnitudes of fugitive methane emission. These data show spatial variability through the years and minor influences of seasonal changes on methane emissions. Methane emissions are typically lowest in the summer and higher in the winter or spring, but do not show a statistically significant correlation. The literature points to microbial activity creating and oxidizing methane at landfill facilities during certain temperature and precipitation conditions. These findings contribute to the identification of fugitive methane emissions from landfills by further understanding microbial bacteria in the soil. This project attempted to find environmental influences on methane emissions at landfills. Many of the results showed weak and inconsistent relationships between environmental variables and fugitive methane emissions. Therefore, environmental variables cannot be shown to be the dominant control of fugitive methane emissions and landfill owners and operators should focus on wellhead maintenance during the required monitoring due to higher averaged emissions from the CARB dataset.