# Strategies for the Sustainable Management of the Organic Fraction of Municipal Waste
## 3 Results and Discussions
### Raw Materials
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Mixture** & **C/N** & \begin{tabular}{c} **Vtotal** \\ **(m\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **VPO** \\ **(m\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **Vpruning** \\ **(m\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **VOFMW** \\ **(m\({}^{3}\))** \\ \end{tabular} & \begin{tabular}{c} **Weight\({}_{\text{pruning}}\)** \\ **(kg)** \\ \end{tabular} & \
\begin{tabular}{c} **Weight\({}_{\text{pruning}}\)** \\ **(kg)** \\ \end{tabular} &
\begin{tabular}{c} **Weight\({}_{\text{pruning}}\)** \\ **(kg)** \\ \end{tabular} \\ \hline
40\% PO \({}^{*}\), 40\% & \multirow{4}{*}{22.34} & \multirow{4}{*}{3.6} & \multirow{4}{*}{1.4} & \multirow{4}{*}{0.7} & \multirow{4}{*}{302} & \multirow{4}{*}{216} & \multirow{4}{*}{468} \\ pruning, 20\% & & & & & & & & \\ OFMW \({}^{*}\) & & & & & & & & \\ \hline
50\% PO \({}^{*}\), 50\% & \multirow{4}{*}{40.87} & \multirow{4}{*}{3.6} & \multirow{4}{*}{1.8} & \multirow{4}{*}{1.8} & \multirow{4}{*}{0} & \multirow{4}{*}{378} & \multirow{4}{*}{270} & \multirow{4}{*}{0} \\ pruning, 30\% & & & & & & & & \\ OFMW \({}^{*}\) & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mixtures chosen for the experimental test for each pile. Table 3 shows the Matrix of PCA obtained with N, C, EC, and pH in all mixtures. PC1, which explained 51.1% of the variation, significantly separated all mixtures (\(p<0.01\)). This PC1 was related to C and N (Table 3), indicating that all mixtures were separated from the beginning of the composting process up to the final compost by C and N contents. PC2, which explained 35.7% of the variation, significantly separated the different sampling dates related to changes in pH and EC. Thus, pH and EC were the properties that significantly changed over time, with overall increases in pH and decreases  
Figure 2: Trial progress; analytical data. (a) %C; (b) %N; (c) C/N; (d) pH; (e) EC. in EC. The PCA performed (Figure 3) showed that 86.8% of the total variation could be explained by the first two PCs. The content of C decreased during the composting process, as previously reported [23], but decreases were in the same proportion in all mixtures, maintaining the separation of all mixtures throughout the whole process based on C and N. A well-matured compost should present a C/N ratio of \(<\)20, and so mixture 2 would indicate a poor maturity compost [24]. At the end of the test, the quality parameters required by [18] (Table 4) were analyzed; these refer to metals and microorganisms, with optimum quality values being obtained in all cases which were well below the limits of the legislation, as several authors have also found and collected in the review [25]. The nutrients were also analyzed to establish the richness of the compost obtained and its value for possible uses. Table 5 shows that mixture 3 had a higher nutritional power in terms of NPK values, which were similar to the values found in the bibliography [26]. Figure 3: PCA factor scores of variations in C, N, pH, and EC in the three mixtures studied. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **PC1** & **PC2** \\  & **(51.1\%)** & **(35.7\%)** \\ \hline N & 0.911 & \(-\)0.044 \\ \hline C & 0.906 & 0.139 \\ \hline EC & \(-\)0.152 & 0.942 \\ \hline pH & \(-\)0.480 & \(-\)0.850 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Matrix of PCA obtained with N, C, EC, and pH in all mixtures.