## 3 Results and Discussion  
### GHG Emissions under Each Scenario  
In this paper, using the existing model of MSW disposal in Beijing as the standard scenario, four scenarios of collection, transportation, and disposal of waste after integrating two systems were designed. Using the guidance method of the IPCC and the LCA framework, the GHG emissions from collection, transportation, and disposal of MSW under the five scenarios in Beijing were estimated and compared. The results are shown in Figure 7, and data are shown in Table 9. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Notation** & **Description** & **Typical Values** \\ \hline \(E_{l}\) & GHG emissions in incineration (\(t\)) & — \\ \(E_{i}\) & Direct emissions from mineral carbon incineration (\(t\)) & — \\ \(E_{e}\) & GHG emissions reduction from electricity generation (\(t\)) & — \\ \(MSW_{i}\) & Mass of waste incinated (\(t\)) & shown in Table 3 \\ \(f_{i}\) & Waste composition & shown in Table 4 \\ \(dm_{i}\) & Dry matter content of wet weight & shown in Table 1 \\ \(CF_{i}\) & DOC content of dry weight & shown in Table 1 \\ \(FCF_{i,t}\) & Fossil carbon fraction of total carbon & shown in Table 1 \\ \(OF_{w}\) & Oxidation factor & 0.95 \\ \(AD_{e}\) & Mass of on-grid energy from incineration (\(MWh\)) & — \\ \(EF_{e}\) & Electricity GHG emissions factor (\(ICO_{2}\)/\(MWh\)) & 0.4506 \\ \(HV_{MSW}\) & Heat value (\(k\)/\(kg\)\(MSW\)) & shown in Table 4 \\ \(\xi\) & Heat efficiency for incineration plant & 20\% \\ \(\zeta\) & Self-used electricity rate for incineration plant & 20\% \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Relevant parameters of GHG emissions calculation model for MSW incineration. Under the five scenarios, the GHG emissions were 4781.37-16387.68 t, with the highest emissions under Scenario 1 and the lowest under Scenario 5. Compared with the situation under Scenario 1, the GHG emissions under Scenario 2, which included recycling of some of the kitchen waste, were reduced by 1764.59 t, and the emission reduction increased with the increase of separation rate of kitchen waste. Under Scenario 3, the disposal via landfill was removed, and the emission reduction compared with Scenario 1 increased significantly to 7759.95 t. Compared to Scenario 2, the benefit of the GHG emission reduction for Scenario 3 was more significant, because the incineration treatment totally replaced landfill. The emission reduction under Scenario 4 was 6791.33 t. Although the recycling resources were separated, the total emissions were still greater than those under Scenario 3, which reflects the advantages of waste incineration. Scenario 5 was the optimal approach. In the case of increasing kitchen waste and recyclable resources, all the residue waste was incinerated, with the emission reduction of 11606.31 t. Relative to Scenario 3, Scenario 5 further reduced emissions by 3846.36 t, which was resulted from the recycling of recyclable resources. When considering the emission reduction benefits of electricity generation from waste and recycling of renewable resources, the net emissions under Scenario 1 to Scenario 5 were successively reduced. Of incineration, landfill, and composting, composting had the lowest GHG emissions per unit (0.117 t), followed by incineration (0.3690-0.5181 t), and landfill had the highest GHG emissions per unit (1.2252-1.2803 t). Therefore, increasing the disposal amount of incineration and composting would lead to an emission reduction effect. [PERSON] et al. found that sanitary landfill's carbon emissions were more than thrice those of composting, and more than twice those generated during burning [20]. In the case of Shanghai, the research also shew the same conclusion that the landfill treatment should be replaced by incineration and composting [56]. So improving the rate of incineration and composting was important to reduce GHG emissions.