Biochemical　decomposition　of　high　kitchen　wastes　in　landfills　in　China　results　in　(i)　a　high　content　of　vapor　in　landfill　gas　(LFG)　and　(ii)　a　noticeable　temperature　gradient　across　the　earthen　final　cover　(EFC).　Yet,　it　is　unclear　how　vapor　and　temperature　gradients　affect　moisture　and　gas　transport　through　EFC　and　microbial　aerobic　methane　oxidation　(MAMO).　A　theoretical　model　of　moisture-gas-heat　reactive　transport　considering　MAMO　and　effects　of　vapor　flow　and　temperature　gradients　was　developed,　and　a　series　of　parametric　studies　were　included.　The　model　was　verified　by　published　test　results.　The　parametric　simulation　results　show　that　vapor　from　landfill　wastes　can　replenish　water　to　EFCs　in　dry　seasons,　which　results　in　(i)　the　relief　of　water　shortage　of　vegetation　and　MAMO　and　(ii)　LFG　emission　reduction.　Effects　of　vapor　inflow　become　more　significant　under　larger　temperature　gradient.　In　cold　seasons,　temperature　gradients　can　promote　MAMO　to　reduce　methane　emissions,　and　enhance　evaporation　to　reduce　percolation.　When　evaporation　rate　at　the　surface　exceeds　30　times　vapor　influx,　vapor　inflow　has　negligible　effects　on　moisture　and　gas　transport　in　EFCs.　Neglecting　effects　of　vapor　and　temperature　gradient　can　lead　to　misjudgments　on　anti-seepage　performance　and　methane　emission　reduction　performance　of　EFCs.　©　2022