Mechanically-biologically treated municipal solid waste as a support medium for microbial methane oxidation to mitigate landfill greenhouse emissions

The residual fraction of mechanically-biologically treated municipal solid waste (MBT residual) was studied in the laboratory to evaluate its suitability and environmental compatibility as a support medium in methane (CH4) oxidative biocovers for the mitigation of greenhouse gas emissions from landfills. Two MBT residuals with 5 and 12 months total (aerobic) biological stabilisation times were used in the study. MBT residual appeared to be a favourable medium for CH4 oxidation as indicated by its area-based CH4 oxidation rates (12.2-82.3 g CH4 m(-2) d(-1) at 2-25 degrees C; determined in CH4-sparged columns). The CH4 oxidation potential (determined in batch assays) of the MBT residuals increased during the 124 d column experiment, from <1.6 to a maximum of 104 mu g CH4 g(dw)(-1) h(-1) (dw = dry weight) at 5 degrees C and 578 mu g CH4 g(dw)h(-1) at 23 degrees C. Nitrous oxide (N2O) production in MBT residual (< 15 mu g N2O kg(dw)(-1)d(-1) in the CH4 dw oxidative columns) was at the lower end of the range of N2O emissions reported for landfills and non-landfill soils, and insignificant as a greenhouse gas source. Also, anaerobic gas production (25.6 l kg(dw)(-1) during 217 d) in batch assays was low, indicating biological stadw bility of the MBT residual. The electrical conductivities (140-250 mS m(-1)), as well as the concentrations of zinc (3.0 mg l(-1)), copper (0.5 mg l(-1)), arsenic (0.3 mg l(-1)), nickel (0.1 mg l(-1)) and lead (0.1 mg l(-1)) in MBT residual eluates from a leaching test (EN-12457-4) with a liquid/solid (L/S) ratio of 10:1, suggest a potential for leachate pollutant emissions which should be considered in plans to utilise MBT residual. In conclusion, the laboratory experiments suggest that MBT residual call be utilised as a support medium for CH4 oxidation, even at low temperatures, to mitigate greenhouse gas emissions from landfills. (c) 2007 Elsevier Ltd. All rights reserved.