HDPE membrane is now commonly used in sanitary landfills,although there has been insufficient evaluation of its effect on GHG emissions.In this study,GHG emission scenarios were investigated at the Dongbu landfill,using three different cover material scenarios: HDPE covering,at an 88%coverage rate; no covering,on the working face; and a novel material-OWC as a trial material.Results showed that the HDPE membrane produced a high CH4 retention,99.8%(CH4 mean flux of 12.24 mgC m-2·h-1)compared with the air-permeable OWC surface(mean flux of 5932.8 mg C m-2·h-1),given the same landfill age.Newly dumped waste at the working face tended to emit a large fraction of N2O,with average fluxes of 10.42 mgN m-2·h-1,while N2O emissions were minuscule at both the HDPE and the OWC sites.At the OWC site CH4 emissions were elevated under high temperatures but gradually dropped as landfill age increased.The massive presence of CO2 at both the working face and the OWC site suggested that the decomposition of organic matter is sustained by the continual dumping of fresh waste.Most importantly,the annual GHG emissions were 9.71 Gg yr-1 in CO2 equivalents for the landfill as a whole,of which the OWC-covered site contributed the most CH4(41.8%),and the working face contributed the most N2O(97.2%).HDPE membrane is therefore a highly recommended capping material for GHG control.