## 2 Materials and Methods
### Analytical Measurements  
The contents of dry matter as well as its organic and mineral compounds were determined with the gravimetric method. The content of total carbon, organic carbon, and total nitrogen were assayed using a Flesh 2000 analyzer (Thermo Fisher Scientific, Waltham, MA, USA). Protein content was computed by multiplying nitrogen content by a conversion factor of 6.25. Total phosphorus content was determined colorimetrically in ammonium metavanadate (V) and ammonium molybdate, whereas to determine the content of reducing sugars, a method with an anthrone reagent using a DR 2800 spectrophotometer (HACH Lange) was employed. The content of lipids was determined with the Soxhlet  
Figure 3: The anaerobic batch respirometric reactors (AMPTS II) used in stage 1 of the study, including: (**a**) anaerobic incubation unit; (**b**) ex situ CO\({}_{2}\) absorption unit; (**c**) CH\({}_{4}\) production measurement unit; (**d**) software with a data collection and analysis system.  
method (Buchi, Switzerland), whereas biogas composition was determined by means of a GC Agillent 7890 A gas chromatograph.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multirow{2}{*}{**Unit**} & \multicolumn{2}{c}{**Value**} \\ \cline{3-4}  & & **Mowing/Stage 1** & **Hacking/Stage 2** \\ \hline Moving area & ha/year & 2045 & 198 \\ \hline FM mass & MgFM/ha & 18.0 & 6.4 \\ \cline{2-4}  & MgFM/year & 36,806 & 1267 \\ \hline TS content & \%FM & 27.3 & 18.4 \\ \hline TS mass & MgTS/ha & 4.90 & 1.20 \\ \cline{2-4}  & MgTS/year & 10,020 & 240 \\ \hline VS content & \%TS & 84.3 & 87.1 \\ \hline VS mass & MgVS/ha & 4.10 & 1.10 \\ \cline{2-4}  & MgVS/year & 8425 & 210 \\ \hline
**Parameter** & **Unit** & **Value** \\ \hline CH\({}_{4}\) energy & kWh/m\({}^{3}\) & 9.17 \\ \hline Thermal efficiency in cogeneration & \% & 43 \\ \hline Electric efficiency in cogeneration & \% & 38 \\ \hline Heat consumption for process purposes & \% gross energy & 30 \\ \hline Electric energy consumption for process purposes & \% gross energy & 9 \\ \hline Generator operating time & h/year & 8000 \\ \hline \hline \end{tabular}
\end{table}
Table 4: The input data for the mass-energy balance.  
\begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{1}{c}{**Indicator**} & \multicolumn{1}{c}{**Unit**} & \multicolumn{1}{c}{**Computation Method**} \\ \hline  & & substrate mass (MgFM/year) \\  & & \(\times\)percentage content of TS (\%FM) \\ Annual methane production & m\({}^{3}\)/year & \(\times\)percentage content of VS (\%TS) \\  & & \(\times\) biogas production potential (m\({}^{3}\)/MgVS) \\  & & \(\times\)methane fraction in biogas (\%) \\ \hline Annual energy production & kWh/year & annual methane production (m\({}^{3}\)/year) \\  & & \(\times\)methane calorific value (9.17 kWh/m\({}^{3}\)) \\ \hline Theoretical thermal power & kW & methane production per hour (m\({}^{3}\)/h) \\  & & \(\times\)methane calorific value (9.17 kWh/m\({}^{3}\)) \\  & & \(\times\)thermal efficiency in co-generation (43\%) \\ \hline Theoretical electric power & kW & methane production per hour (m\({}^{3}\)/h) \\  & & \(\times\)methane calorific value (9.17 kWh/m\({}^{3}\)) \\  & & \(\times\)electric efficiency in co-generation (38\%) \\ \hline \multicolumn{3}{c}{theoretical thermal power (kW)} \\ Gross heat production & GJ/year & \(\times\)operation time (8000 h) \\  & & \(\times\)3.6 (unit conversion from kWh to GJ) \\ \hline Heat consumption for process purposes & GJ/year & gross heat production \(\times\) 0.3 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Methodology of estimating energy indicators.