Time filter

Source Type

Wheaton, IL, United States

Chanton J.P.,Florida State University | Hater G.,Waste Management Inc. | Green R.,Waste Management Inc. | Bogner J.,Landfills Inc.
Geotechnical Special Publication | Year: 2010

Microbial methane oxidation in landfill cover soil is a very effective approach for reducing emissions from landfills. Oxidation of methane may be enhanced by the application of materials present on site, such as yard waste or compost. Engineers require a method to quantify methane oxidation in different types of covers. In this paper we will present a simple, effective stable isotope technique for the evaluation of cover soil methane oxidation. The approach exploits systematic variations in the ratio of 13C/ 12C in CH4 prior to and following exposure to methane oxidizing microbes in the soil. The action of the bacteria increases this ratio, due to their preference for utilizing 12CH4 rather than 13CH4. The shift in the ratio following oxidation is proportional to the amount of CH4 oxidized. © 2010 ASCE.

Spokas K.,U.S. Department of Agriculture | Spokas K.,University of Minnesota | Bogner J.,Landfills Inc. | Bogner J.,University of Illinois at Chicago | Chanton J.,Florida State University
Journal of Geophysical Research: Biogeosciences | Year: 2011

We have developed and field-validated an annual inventory model for California landfill CH4 emissions that incorporates both site-specific soil properties and soil microclimate modeling coupled to 0.5 scale global climatic models. Based on 1-D diffusion, CALMIM (California Landfill Methane Inventory Model) is a freely available JAVA tool which models a typical annual cycle for CH4 emissions from site-specific daily, intermediate, and final landfill cover designs. Literature over the last decade has emphasized that the major factors controlling emissions in these highly managed soil systems are the presence or absence of engineered gas extraction, gaseous transport rates as affected by the thickness and physical properties of cover soils, and methanotrophic CH4 oxidation in cover materials as a function of seasonal soil microclimate. Moreover, current IPCC national inventory models for landfill CH4 emissions based on theoretical gas generation have high uncertainties and lack comprehensive field validation. This new approach, which is compliant with IPCC "Tier III" criteria, has been field-validated at two California sites (Monterey County; Los Angeles County), with limited field validation at three additional California sites. CALMIM accurately predicts soil temperature and moisture trends with emission predictions within the same order of magnitude as field measurements, indicating an acceptable initial model comparison in the context of published literature on measured CH4 emissions spanning 7 orders of magnitude. In addition to regional defaults for inventory purposes, CALMIM permits user-selectable parameters and boundary conditions for more rigorous site-specific applications where detailed CH4 emissions, meteorological, and soil microclimate data exist. Copyright 2011 by the American Geophysical Union.

Reddy K.R.,University of Illinois at Chicago | Hettiarachchi H.,Lawrence Technological University | Gangathulasi J.,University of Illinois at Chicago | Bogner J.E.,Landfills Inc. | Bogner J.E.,University of Illinois at Chicago
Waste Management | Year: 2011

This paper presents the results of laboratory investigation conducted to determine the variation of geotechnical properties of synthetic municipal solid waste (MSW) at different phases of degradation. Synthetic MSW samples were prepared based on the composition of MSW generated in the United States and were degraded in bioreactors with leachate recirculation. Degradation of the synthetic MSW was quantified based on the gas composition and organic content, and the samples exhumed from the bioreactor cells at different phases of degradation were tested for the geotechnical properties. Hydraulic conductivity, compressibility and shear strength of initial and degraded synthetic MSW were all determined at constant initial moisture content of 50% on wet weight basis. Hydraulic conductivity of synthetic MSW was reduced by two orders of magnitude due to degradation. Compression ratio was reduced from 0.34 for initial fresh waste to 0.15 for the mostly degraded waste. Direct shear tests showed that the fresh and degraded synthetic MSW exhibited continuous strength gain with increase in horizontal deformation, with the cohesion increased from 1. kPa for fresh MSW to 16-40. kPa for degraded MSW and the friction angle decreased from 35° for fresh MSW to 28° for degraded MSW. During the triaxial tests under CU condition, the total strength parameters, cohesion and friction angle, were found to vary from 21 to 57. kPa and 1° to 9°, respectively, while the effective strength parameters, cohesion and friction angle varied from 18 to 56. kPa and from 1° to 11°, respectively. Similar to direct shear test results, as the waste degrades an increase in cohesion and slight decrease in friction angle was observed. Decreased friction angle and increased cohesion with increased degradation is believed to be due to the highly cohesive nature of the synthetic MSW. Variation of synthetic MSW properties from this study also suggests that significant changes in geotechnical properties of MSW can occur due to enhanced degradation induced by leachate recirculation. © 2011 Elsevier Ltd.

Bogner J.E.,Landfills Inc. | Bogner J.E.,University of Illinois at Chicago | Spokas K.A.,University of Minnesota | Chanton J.P.,Florida State University
Journal of Environmental Quality | Year: 2011

Compared wiThnatural ecosystems and managed agricultural systems, engineered landfills represent a highly managed soil system for which there has been no systematic quantification of emissions from coexisting daily, intermediate, and final cover materials. We quantified the seasonal variability of CH4, CO2, and N2O emissions from fresh refuse (no cover) and daily, intermediate, and final cover materials at northern and southern California landfill sites wiThengineered gas extraction systems. Fresh refuse fluxes (g m-2 d-1 [± SD]) averaged CH4 0.053 (± 0.03), CO2 135 (± 117), and N2O 0.063 (± 0.059). Average CH4 emissions across all cover types and wet/dry seasons ranged over more than four orders of magnitude (<0.01-100 g m-2 d-1) wiThmost cover types, including boThfinal covers, averaging <0.1 g m-2 d-1 wiTh10 to 40% of surface areas characterized by negative fluxes (uptake of atmospheric CH4). The northern California intermediate cover (50 cm) had the highest CH4 fluxes. For boThthe intermediate (50-100 cm) and final (>200 cm) cover materials, below which methanogenesis was well established, the variability in gaseous fluxes was attributable to cover thickness, texture, density, and seasonally variable soil moisture and temperature at suboptimal conditions for CH4 oxidation. Thin daily covers (30 cm local soil) and fresh refuse generally had the highest CO2 and N2O fluxes, indicating rapid onset of aerobic and semi-aerobic processes in recently buried refuse, wiThrates similar to soil ecosystems and windrow composting of organic waste. This study has emphasized the need for more systematic field quantification of seasonal emissions from multiple types of engineered covers. © 2011 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Bogner J.E.,University of Illinois at Chicago | Bogner J.E.,Landfills Inc. | Chanton J.P.,Florida State University | Blake D.,University of California at Irvine | And 2 more authors.
Environmental Science and Technology | Year: 2010

Methane-oxidizing "biocovers" were constructed at the Leon County Landfill (Florida). The primary goal was to determine if a biocover placed above the existing thin (15 cm) intermediate clay cover would be capable of mitigating CH4 and nonmethane hydrocarbon (NMHC) emissions to the atmosphere in this subtropical environment. A secondary goal was to maximize the use of locally recycled materials for biocover construction. The biocovers consisted of 30 or 60 cm of ground garden waste placed over a 15 cm gas distribution layer (clean crushed recycled glass from discarded fluorescent lights). The deep biocover reduced methane fluxes relative to the controls during temporal monitoring over more than a year; in large part, thesereductionswereattributabletoincreasedmethaneoxidation. Both the shallow and the deep biocover exhibited significant percentages of negative fluxes (uptake of atmospheric methane) relative to the nonbiocover controls which had consistently positive fluxes. The overall annual effectiveness/performance of the biocover was limited by seasonally high moisture contents and the thin gas distribution layer. For NMHCs, the deep biocover demonstrated substantial reductions for nonmethane hydrocarbon emissions with high percentages of negative fluxes for several hydrocarbon groups, especially the aromatics, alkanes, and lower chlorinated compounds. Ranges of measured NMHC emissions (10-9 to 10-3 g m-2 d-1) were similar to previous studies in the literature. Conservative calculations based on field data for total NMHC emissions from the 60 cm biocover area indicate that current U.S. Environmental Protection Agency (EPA) regulatory methods overestimate emissions by more than 2 orders of magnitude, suggesting that improved field-validated methods are needed. © 2010 American Chemical Society.

Discover hidden collaborations