Quantifying greenhouse gas (GHG) emissions in waste sector is important to evaluating measures for reduction of GHG emissions. To forecast GHG emissions and identify potential emission reduction for GHG emissions, scenarios applied with environmental policy such as waste reduction and structure change of waste treatment were developed. Scenario I estimated GHG emissions under business as usual (BAU) baseline. Scenario II estimated GHG emissions applied the waste reduction policy and scenario III was under the policy of structure change of waste treatment. Scenario IV was based on the policy of waste reduction and structure change of waste treatment. As for the different scenarios, GHG emissions were highest under scenarios III, followed by scenarios IV, I, and II. Particularly, GHG emissions under scenario III increased due to the increased GHG emissions from the enhanced waste incineration by structure change of waste treatment. This result indicated that the waste reduction is primary policy for GHG reduction from waste. GHG emission from landfill was highest compared to those from incineration. However, the contribution of GHG emission from incineration increased under scenario III and IV. This indicated that more attention should be paid to the waste treatment for incineration to reduce GHG emissions. Quantifying greenhouse gas (GHG) emissions in waste sector is important to evaluating measures for reduction of GHG emissions. To forecast GHG emissions and identify potential emission reduction for GHG emissions, scenarios applied with environmental policy such as waste reduction and structure change of waste treatment were developed. Scenario I estimated GHG emissions under business as usual (BAU) baseline. Scenario II estimated GHG emissions applied the waste reduction policy and scenario III was under the policy of structure change of waste treatment. Scenario IV was based on the policy of waste reduction and structure change of waste treatment. As for the different scenarios, GHG emissions were highest under scenarios III, followed by scenarios IV, I, and II. Particularly, GHG emissions under scenario III increased due to the increased GHG emissions from the enhanced waste incineration by structure change of waste treatment. This result indicated that the waste reduction is primary policy for GHG reduction from waste. GHG emission from landfill was highest compared to those from incineration. However, the contribution of GHG emission from incineration increased under scenario III and IV. This indicated that more attention should be paid to the waste treatment for incineration to reduce GHG emissions.