## 2 Materials and Methods
### Co-Composting Set Up and Monitoring  
The co-composting was carried out at \"Gorini Piante\" facilities (Pistoia, Italy), where three piles (6 m\({}^{3}\) each) were designed as follows (_v-v_): A = 3S:1 GW; B = 1S:1 GW; C = 1S:3 GW. Urea (1 kg per m\({}^{3}\)) was added to each pile, to facilitate the composite process in its initial phase. The piles were regularly homogenized, and the temperature was monitored as reported in [PERSON] et al. [17] (2023). The temperatures were measured during co-composing using a thermometer (Checktemp(r)1, Hanna Instruments, Padova, Italy). The probe was inserted at least 1 m deep inside each pile to obtain a representative measure of the entire pile mass. Samples from each pile were collected before starting the co-composting and after 4 (T4), 30 (T30), 60 (T60), and 100 (T100) days, until the reduction in the total enzyme activities occurred as observed in [PERSON] et al. [17] (2023). At each sampling time, the pH, electrical conductivity (EC), total nitrogen (TN), total organic carbon (TOC), TOC/TN, and humic acids (HA) were assessed. The germination index (GI) was only measured at T100.  
One hour of water extraction (1:5 _v-v_) was carried out at room temperature for EC and pH determination. Afterwards, specific electrodes were used (EC: Hanna Instruments, Padova, Italy; pH: SevenMulti, Mettler Toledo, Milano, Italy). TOC and TN were determined by dry combustion using a FlashSmart elemental analyzer (Thermo Fisher Scientific, Milan, Italy). HAs were determined on co-compost samples (1 g) by extraction with 0.05 M sodium pyrophosphate (pH = 9) overnight. H\({}_{2}\)SO\({}_{4}\) was added to the surnatant and titration with 0.5 N Mohr salt was carried out [32] ([PERSON] et al., 1996). The hydrocarbon (C \(>\) 12) concentrations were determined using a gas chromatography-mass spectrometry (GC-MS) [33] (EPA 8270 E, 2018). Trace 1300 instrument with AS 3000 autosampler (Thermo Scientific, Waltham, MA, USA), following the official method [34] (UNI EN 14039, 2005). The GI was determined on seedling roots and seed of _Lepidium sativum_ incubated for 72 h at 25 \({}^{\circ}\)C on co-compost water extract (1:5, _v-v_) in Petri dishes [35] ([PERSON] et al., 2002).  
\begin{table}
\begin{tabular}{l l l l} \hline Chemical Parameters & \multicolumn{1}{c}{**S**} & \multicolumn{1}{c}{**GW**} \\ \hline pH & & 7.68 \(\pm\) 0.04 & 6.51 \(\pm\) 0.01 \\ EC & dS/m & 4.20 \(\pm\) 0.02 & 0.17 \(\pm\) 0.01 \\ TOC & \% & 1.41 \(\pm\) 0.03 & 34.1 \(\pm\) 5.7 \\ TN & \% & 0.18 \(\pm\) 0.01 & 1.64 \(\pm\) 0.02 \\ TOC/TN & & 7.83 & 20.8 \\ \hline \multicolumn{4}{l}{Organic contamination} \\ \hline C \textgreater{} 12 & \multicolumn{1}{c}{mg kg\({}^{-1}\)} & \multicolumn{1}{c}{\(133.5\pm 10.2\)} \\ PCB & \multicolumn{1}{c}{mg kg\({}^{-1}\)} & \multicolumn{1}{c}{\(<\)LOD} \\ \hline Heavy metals & & & \\ \hline Cu & & 56.6 \(\pm\) 4.7 & 35.3 \(\pm\) 5.6 \\ Zn & & 108 \(\pm\) 1.0 & 24.6 \(\pm\) 2.4 \\ Cd & \multicolumn{1}{c}{mg kg\({}^{-1}\)} & \multicolumn{1}{c}{\(<\)LOD} \\ Ni & & 50.8 \(\pm\) 1.0 & 7.02 \(\pm\) 0.30 \\ Pb & & 16.6 \(\pm\) 0.7 & 3.11 \(\pm\) 0.91 \\ Cr & & 58.5 \(\pm\) 5.6 & 19.3 \(\pm\) 3.1 \\ \hline \end{tabular}  
* EC = electrical conductivity; TOC = total organic carbon; TN = total nitrogen; C \textgreater{} 12 = hydrocarbons C \textgreater{} 12; PCB = total polychloro biphenyls; LOD = limit of detection.  
\end{table}
Table 1: Properties of the dredged sediments (S) and green waste (GW) used in the co-composting.