## 2 Materials and Methods
### Organization of the Experiment, Description of the Analytical Methods  
The composting process was rigorously monitored, focusing on the changes in the temperature and mass of the composting substrate, as well as the chemical properties of both the substrate and the generated leachate. The chemical properties of the waste were evaluated at five-day intervals to ensure a thorough analysis. For this purpose, samples averaging 775 g were collected from various locations within the reactor to ensure that they were representative of the entire reactor. These samples were mixed prior to the analyses to ensure their homogeneity and representativeness of the entire substrate mass. The analyses were then performed in triplicate to ensure the reliability and accuracy of the results. The characteristics that were analysed included the following:  
1. Percent moisture, measured by drying the sample at 105 \({}^{\circ}\)C for 24 h and determining the evaporated water loss by weighing the difference to an accuracy of 0.1 g (ISO 11465:1993) [25];
2. Share of volatile substances, measured by loss on ignition, by milling a dried sample to a size of \(<\)1 mm and heating at 550 \({}^{\circ}\)C for 6 h LOI (ISO 10694:1995) [26]; loss of volatiles was determined with an accuracy of 0.0001 g;
3. Share of total organic carbon, TOC, measured by burning a dried and milled sample at 900 \({}^{\circ}\)C in a Shimadzu TOC-V\({}_{\text{CSN}}\) carbon analyser with an SSM-5000A module and determining the TOC by subtracting the inorganic carbon content from the total carbon content (ISO 10694:1995) [26];
4. Four-day respirometric activity, AT4, determined by the manometric method using a WWT Oxi-Top Control kit (Xylem Analytics Germany Sales GmbH & Co. KG; Weilheim, Germany); the analysis consisted of incubating samples for 4 days at 22 \({}^{\circ}\)C in the presence of a 1M NaOH solution (ISO 16072:2002) [27]. The leachate was collected each day, and the following characteristics were analysed:  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Component**} & **Bulk Density** & **Mass** & **Volume** & **Moisture** & **Share** \\  & **[kg\(\cdot\)m\({}^{-3}\)]** & **[kg]** & **[L]** & **[\%]** & **[\%**\(w\)**\(w\)**]** \\ \hline Kitchen waste & 750 & 115 & 153.3 & 78.0 & 59.0 \\ Leaves & 200 & 55 & 275.0 & 56.6 & 28.2 \\ Deciduous wood chips * & 195 & 15 & 76.9 & 40.2 & 7.7 \\ Coniferous wood chips * & 215 & 10 & 46.5 & 25.3 & 5.1 \\ \hline Final substrate ** & 381.7 & 195 & 551.8 & 66.3 & 100.0 \\ \hline \hline \end{tabular}  
* * Wood waste mechanically ground to a grain size of \(<\)15 mm, ** estimated based on the characteristics of the individual components.  
\end{table}
Table 1: Characteristics of individual components of the test substrate.  
1. pH, determined by the potentiometric method (ISO 10523:2008) [28];
2. Chemical oxygen demand (COD), determined using the dichromatic method (ISO 6060:1989) [29];
3. Ammonium nitrogen content, determined by steam distillation followed by titration with 0.01 N sodium hydroxide solution in the presence of Tashiro reagent as an indicator, (ISO 5664:1984) [30];
4. Volatile fatty acids (VFA) content, determined by steam distillation followed by titration with 0.01 N sodium hydroxide solution in the presence of phenolphthalein as an indicator (APHA 5560) [31];
5. Phosphates, determined by a spectrophotometric method (ISO 6878:2004) [32].  
Additionally, to monitor changes in the granularity of the substrate, fractional analysis was performed three times: at the start of the experiment, on the 30 th day, and on the 45 th day of the process. This analysis was performed manually with sieves, using the following size fractions: (i) <10 mm, (ii) 10-40 mm, (iii) 40-60 mm, (iv) 60-80 mm, (v) 80-100 mm, and (vi) >100 mm.