## 3 Results
### Co-Compost Maturity and Stability
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Pile**} & \multicolumn{4}{c}{**Sampling Time**} \\ \hline  & & **4** & **30** & **60** & **100** \\ \hline \multirow{4}{*}{pH} & A & 8.2 \(\pm\) 0.13 Cb & 7.9 \(\pm\) 0.23 Bb & 7.2 \(\pm\) 0.15 Aa & 7.4 \(\pm\) 0.08 ABa \\  & B & 7.7 \(\pm\) 0.13 Bb & 7.5 \(\pm\) 0.03 Aa & 7.4 \(\pm\) 0.04 Ba & 7.5 \(\pm\) 0.03 Ba \\  & C & 7.3 \(\pm\) 0.16 Aa & 7.4 \(\pm\) 0.00 Aa & 7.3 \(\pm\) 0.06 ABa & 7.3 \(\pm\) 0.15 Aa \\ \hline \multirow{4}{*}{EC} & A & 3.0 \(\pm\) 0.29 Ba & 3.0 \(\pm\) 0.33 Ca & 2.9 \(\pm\) 0.21 Ca & 2.7 \(\pm\) 0.2 Ca \\  & B & 2.3 \(\pm\) 0.16 Aa & 2.6 \(\pm\) 0.06 Ba & 2.4 \(\pm\) 0.30 Ba & 2.4 \(\pm\) 0.15 Ba \\  & C & 2.5 \(\pm\) 0.30 Ac & 1.8 \(\pm\) 0.14 Ab & 1.3 \(\pm\) 0.09 Aa & 1.2 \(\pm\) 0.00 Aa \\ \hline \multirow{4}{*}{TOC} & A & 1.72 \(\pm\) 0.63 Aa & 1.72 \(\pm\) 0.04 Aa & 1.65 \(\pm\) 0.05 Aa & 1.86 \(\pm\) 0.06 Aa \\  & B & 4.33 \(\pm\) 1.45 Bab & 4.07 \(\pm\) 0.28 Ba & 5.78 \(\pm\) 0.84 Bb & 3.54 \(\pm\) 0.62 Ba \\  & C & 11.25 \(\pm\) 0.52 Cc & 10.49 \(\pm\) 0.10 Cb & 11.66 \(\pm\) 0.49 Cc & 9.39 \(\pm\) 0.25 Ca \\ \hline \multirow{4}{*}{TN} & A & 0.22 \(\pm\) 0.09 Aa & 0.14 \(\pm\) 0.01 Aa & 0.13 \(\pm\) 0.01 Aa & 0.15 \(\pm\) 0.01 Aa \\  & B & 0.36 \(\pm\) 0.07 Bab & 0.31 \(\pm\) 0.03 Ba & 0.38 \(\pm\) 0.01 Bb & 0.31 \(\pm\) 0.02 Ba \\  & C & 1.17 \(\pm\) 0.08 Cd & 0.74 \(\pm\) 0.02 Cb & 0.71 \(\pm\) 0.00 Cc & 0.58 \(\pm\) 0.02 Ca \\ \hline \multirow{4}{*}{TOC/TN} & A & 8.0 \(\pm\) 7.19 Aa & 12.2 \(\pm\) 2.73 Ab & 12.4 \(\pm\) 2.87 Ab & 12.7 \(\pm\) 4.84 Ab \\  & B & 11.8 \(\pm\) 4.76 Ba & 13.3 \(\pm\) 4.21 ABab & 15.1 \(\pm\) 4.48 Bb & 11.4 \(\pm\) 3.96 Aa \\  & C & 9.6 \(\pm\) 5.69 Aa & 14.2 \(\pm\) 5.08 Bb & 16.4 \(\pm\) 4.12 Cc & 16.2 \(\pm\) 5.20 Bc \\ \hline \multirow{4}{*}{HA} & A & 71.9 \(\pm\) 10.17 Bc & 27.3 \(\pm\) 3.86 Aa & 28.7 \(\pm\) 4.06 Aa & 48.4 \(\pm\) 6.84 ABb \\  & B & 47.6 \(\pm\) 6.73 Aa & 42.1 \(\pm\) 5.95 Ba & 44.8 \(\pm\) 6.34 Ba & 39.6 \(\pm\) 5.60 Aa \\ \cline{1-1}  & C & 56.9 \(\pm\) 8.05 Ab & 50.8 \(\pm\) 7.18 Bab & 41.2 \(\pm\) 5.83 Ba & 52.0 \(\pm\) 7.35 Bab \\ \hline \hline \end{tabular} EC = electrical conductivity (dS m\({}^{-1}\)); TOC = total organic carbon (%); TN = total nitrogen (%); HA = humic acids (%).  
\end{table} 
Table 2: Monitoring of the co-composting chemical properties in 3S:1 GW (A), 1S:1 GW (B) and 1S:3 GW (C) piles (\(\pm\)standard deviation). Different lowercase letters indicate statistically different values (time effect) within each co-compost. Different uppercase letters indicate statistically different values (treatment effect) within each time. Figure 2: Time course of butyrate esterase activity during the co-composting in piles A (3S:1 GW), B (1S:1 GW), and C (1S:3 GW). Different lowercase letters indicate statistically different values (time effect) within each co-compost. Different uppercase letters indicate statistically different values (treatment effect) within each time. Bars represent standard deviation. as ln(NAG)/ln(AP) was above 1 (1.05 \(\pm\) 0.004), while co-compost B and C showed values for ln(NAG)/ln(AP) below 1 (0.96 \(\pm\) 0.012 and 0.93 \(\pm\) 0.005), respectively, resulting more P limited. The C-to N-acquiring enzyme ratio (ln(BG)/ln(NAG)) was below 1 in co-compost A (0.89 \(\pm\) 0.003), confirmed the N-limited condition, while in co-compost B and C, the BG and NAG ratios were close to equilibrium (BG:NAG = 1:1) (B = 0.98 \(\pm\) 0.016; C = 1.01 \(\pm\) 0.011). After 60 days of co-composting, co-compost A showed the values of 1.00 \(\pm\) 0.001 and 0.97 \(\pm\) 0.001 for ln(BG)/ln(NAG) and ln(NAG)/ln(AP) ratios, and as a result, were P-limited. In co-compost B, the ln(BG)/ln(NAG) and ln(NAG)/ln(AP) ratios reached values of 1.02 \(\pm\) 0.016 and 0.93 \(\pm\) 0.013, respectively, shifting from P-limited to C- and P-limited. The co-compost C showed the following values: ln(BG)/ln(NAG) = 1.05 \(\pm\) 0.027 and ln(NAG)/ln(AP) = 0.92 \(\pm\) 0.01, remaining in C- and P-limited conditions.