Landfill CH4 oxidation by mineralized refuse: Effects of NH4+[sbnd]N incubation, water content and temperature

Abstract

Mineralized refuse, excavated from a municipal solid waste (MSW) landfill that had been closed for more than 10years, was incubated in livestock wastewater for 150d to accumulate ammonia-oxidizing bacteria and also co-oxidize methane (CH4). The extent of CH4 oxidation and carbon dioxide (CO2) emissions from the incubated mineralized refuse (IMR) were investigated to assess its applicability as a bio-cover material at landfill sites for minimizing total greenhouse gas emission equivalents. From the initial 200mg nitrogen (N) kg−1 incubated for 120h, the nitrate-N content produced in the IMR was twice (P<0.05) that of the untreated original mineralized refuse (OMR) and 3.81 (P<0.05) times that of soil. For an initial CH4 concentration of approximately 10% by volume in the headspace, CH4 consumption and net emission of CO2 from the soil, IMR and OMR all agreed well with first-order and zero-order kinetics models for a 120-h incubation (R2=0.667 and R2=0.995, respectively). Similar to N turnover, the rate of consumption of CH4 by the mineralized refuse was some 50.0% higher than for soil (P<0.05). Based on the net rate of CO2 generation, the CH4 oxidation rate by IMR was 14.2% (P>0.05) greater than for OMR and 56.1% (P>0.05) higher than for soil. Variation of water content and temperature produced substantially higher CH4 consumption rates by IMR than by either OMR or soil. After treatment by livestock wastewater, the CH4 oxidation capacity of mineralized refuse was moderately improved, due to the enhancement of CH4 adsorption by retained suspended solids and the subsequent co-oxidation by the accumulated ammonia-oxidizing bacteria. By correlation analysis for the three experimental materials, CH4 oxidation rate was significantly correlated with specific surface area and organic matter content (P<0.05), and was positively correlated with CO2 generation, NH4+N nitrification and NO3–N generation rate (P>0.05).