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

摘要

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 (CH_4) 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 CH_4 oxidation as indicated by its area-based CH_4 oxidation rates (12.2-82.3 g CH_4m~(-2)d~(-1) at 2-25 ℃; determined in CH_4-sparged columns). The CH_4 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 μg CH_4 g_(gw)~(-1), h~(-1) (dw = dry weight) at 5 ℃ and 578 μg CH_4 g_(dw)~(-1) hr~(-1) at 23 ℃. Nitrous oxide (N_2O) production in MBT residual (< 15 μg N_2O kg_(dw)~(-1)d~(-1) in the CH_4 oxidative columns) was at the lower end of the range of N_2O emissions reported for landfills and non-landfill soils, and insignificant as a greenhouse gas source. Also, anaerobic gas production (25.6 1 kg_(dw)~(-1) during 217 d) in batch assays was low, indicating biological stability of the MBT residual. The electrical conductivities (140-250 mSm~(-1)), as well as the concentrations of zinc (3.0 mg 1~(-1)), copper (0.5 mg 1~(-1)), arsenic (0.3 mg 1~(-1)), nickel (0.1 mg 1~(-1)) and lead (0.1 mg 1~(-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 can be utilised as a support medium for CH_4 oxidation, even at low temperatures, to mitigate greenhouse gas emissions from landfills.