The　effects　of　different　types　of　earthen　landfill　covers　and　vapor　on　landfill　gas　emissions　are　not　well　understood.　In　this　study,　an　existing　theoretical　model　of　water　and　multicomponent　gas　(methane,　carbon　dioxide,　nitrogen,　and　oxygen)　flow　was　improved　by　incorporating　vapor　flow.　The　model　was　validated　using　a　published　soil　column　test　simulating　landfill　gas　emissions　through　landfill　covers.　Numerical　simulations　were　conducted　to　investigate　landfill　gas　emissions　through　a　single　clay-layer　cover,　a　cover　with　capillary　barrier　effects　(CCBE),　and　a　three-layer　cover　during　continuous　drying.　The　CCBE　retained　the　lowest　water　content　after　drying,　whereas　the　bottom　clay　layer　in　the　three-layer　cover　stayed　almost　saturated　due　to　the　protection　afforded　by　the　top　two　layers.　Accordingly,　methane　emissions　from　the　CCBE　were　the　highest,　whereas　those　from　the　three-layer　cover　were　the　lowest.　Ignoring　vapor　will　predict　a　drier　soil　state,　and　hence　will　cause　methane　emissions　to　be　overestimated　by　1-2.5　times.　Effects　of　vapor　became　more　significant　as　the　overall　gas　coefficient　of　permeability　of　the　cover　increased.