## 3 Results and Discussion
### Anaerobic Digestion
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Indicator**} & \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Unit**} & \multicolumn{4}{c}{**Stage/Variant**} \\ \cline{3-6}  & & & \multicolumn{4}{c}{**Stage 0**} \\ \cline{3-6}  & & & **Variant 1** & **Variant 2** & **Variant 3** \\ \hline \multirow{4}{*}{Biogas} & Rate (r) & cm\({}^{3}\)/gCOD-h & 7.1 \(\pm\) 0.4 & 6.0 \(\pm\) 0.2 & 3.2 \(\pm\) 0.3 \\ \cline{2-6}  & Production rate & [1/h] & 0.10 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 & 0.05 \(\pm\) 0.01 \\ \hline \multirow{4}{*}{Methane} & Methane content & \% & 64.0 \(\pm\) 3.9 & 62.3 \(\pm\) 2.1 & 60.2 \(\pm\) 5.1 \\ \cline{2-6}  & Rate, r & cm\({}^{3}\)/gCOD-h & 0.10 \(\pm\) 0.01 & 0.08 \(\pm\) 0.01 & 0.05 \(\pm\) 0.01 \\ \cline{2-6}  & Production rate & [1/h] & 4.5 \(\pm\) 0.3 & 3.3 \(\pm\) 0.2 & 1.9 \(\pm\) 0.2 \\ \hline \multirow{4}{*}{**Indicator**} & \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Unit**} & \multicolumn{4}{c}{**Stage 1**} \\ \cline{3-6}  & & & **Variant 1** & **Variant 2** & **Variant 3** \\ \hline \multirow{4}{*}{Biogas} & Rate, r & cm\({}^{3}\)/gCOD-h & 7.1 \(\pm\) 0.3 & 6.3 \(\pm\) 0.5 & 4.5 \(\pm\) 0.1 \\ \cline{2-6}  & Production rate & [1/h] & 0.10 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 & 0.07 \(\pm\) 0.01 \\ \hline \multirow{4}{*}{Methane} & Methane content & \% & 70.4 \(\pm\) 2.7 & 69.2 \(\pm\) 4.3 & 67.9 \(\pm\) 3.1 \\ \cline{2-6}  & Rate, r & cm\({}^{3}\)/gCOD-h & 0.10 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 & 0.06 \(\pm\) 0.01 \\ \cline{2-6}  & Production rate & [1/h] & 5.1 \(\pm\) 0.2 & 4.4 \(\pm\) 0.4 & 2.6 \(\pm\) 0.1 \\ \hline \multirow{4}{*}{**Indicator**} & \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Unit**} & \multicolumn{4}{c}{**Stage 2**} \\ \cline{3-6}  & & & **Variant 1** & **Variant 2** & **Variant 3** \\ \hline \multirow{4}{*}{Biogas} & Rate, r & cm\({}^{3}\)/gCOD-h & 8.1 \(\pm\) 0.3 & 7.2 \(\pm\) 0.3 & 6.1 \(\pm\) 0.2 \\ \cline{2-6}  & Production rate & [1/h] & 0.11 \(\pm\) 0.01 & 0.10 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 \\ \hline \multirow{4}{*}{Methane} & Methane content & \% & 69.1 \(\pm\) 2.4 & 69.0 \(\pm\) 4.0 & 67.2 \(\pm\) 3.1 \\ \cline{2-6}  & Rate, r & cm\({}^{3}\)/gCOD-h & 5.1 \(\pm\) 0.2 & 4.5 \(\pm\) 0.3 & 3.6 \(\pm\) 0.2 \\ \cline{2-6}  & Production rate & [1/h] & 0.10 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 & 0.08 \(\pm\) 0.01 \\ \hline \multirow{4}{*}{**Indicator**} & \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Unit**} & \multicolumn{4}{c}{**Stage 3**} \\ \cline{3-6}  & & & **Variant 1** & **Variant 2** & **Variant 3** \\ \hline \multirow{4}{*}{Biogas} & Rate, r & cm\({}^{3}\)/gCOD-h & 8.8 \(\pm\) 0.2 & 7.3 \(\pm\) 0.2 & 6.9 \(\pm\) 0.3 \\ \cline{2-6}  & Production rate & [1/h] & 0.11 \(\pm\) 0.01 & 0.10 \(\pm\) 0.01 & 0.10 \(\pm\) 0.01 \\ \cline{2-6}  & Production rate & [1/h] & 0.10 \(\pm\) 0.01 & 0.10 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 \\ \cline{2-6}  & Constant (k) & [1/h] & 0.10 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 \\ \hline \multirow{4}{*}{**Indicator**} & \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Unit**} & \multicolumn{4}{c}{**Stage 4**} \\ \cline{3-6}  & & & **Variant 1** & **Variant 2** & **Variant 3** \\ \hline \multirow{4}{*}{Biogas} & Rate, r & cm\({}^{3}\)/gCOD-h & 9.0 \(\pm\) 0.2 & 7.7 \(\pm\) 0.3 & 6.5 \(\pm\) 0.2 \\ \cline{2-6}  & Production rate & [1/h] & 0.11 \(\pm\) 0.01 & 0.10 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 \\ \cline{2-6}  & Methane content (k) & [1/h] & 0.11 \(\pm\) 0.01 & 0.10 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 \\ \hline \multirow{4}{*}{**Indicator**} & Methane content & \% & 69.8 \(\pm\) 1.4 & 70.6 \(\pm\) 2.1 & 70.1 \(\pm\) 1.7 \\ \cline{2-6}  & Rate, r & cm\({}^{3}\)/gCOD-h & 5.7 \(\pm\) 0.1 & 4.9 \(\pm\) 0.2 & 4.5 \(\pm\) 0.1 \\ \cline{2-6}  & Production rate & [1/h] & 0.10 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 \\ \cline{2-6}  & Constant (k) & [1/h] & 0.10 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 & 0.09 \(\pm\) 0.01 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Characteristics of the kinetics of AD process in individual experimental variants.