## 3 Results
### Overview of Classified Models  
The considered and classified models are summarized in Tables 1 and 2, separated by top-down and bottom-up modelling approaches [37]. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Ref.** &
\begin{tabular}{c} **View on** \\ **Biogas Plants** \\ \end{tabular} & **Coding/Software** & **Biomass Modeling** & **Region** & **Additional Modeling** \\ \hline
[39] & energy system & oemof [38] & annual chemical biogas potential & northwestern & time-dependent electricity production (wind and photovoltaic) and demand \\ \hline
[40] & energy system & oemof [38] & annual chemical biogas potential & northwestern & time-dependent electricity production (wind and photovoltaic) and demand \\ \hline
[41] & energy system & Engineering Equation & daily chemical biogas potential based on chicken manure and maize silage & - & (photovoltaic), chemical energy production (hydrogen), electrical and thermal energy storage \\ \hline
[41] & energy system & \begin{tabular}{c} Engineering \\ Equation \\ Solver [42] \\ \end{tabular} & \begin{tabular}{c} mainly chemical biogas potential based on \\ chicken manure and \\ maize silage \\ \end{tabular} & \
\begin{tabular}{c} Denmark, \\ Germany, \\ Finland, \\ Norway, \\ Sweden \\ \end{tabular} & - &
\begin{tabular}{c} different waste to energy \\ technologies (e.g., gasification, \\ co-combustion) and other \\ technologies (e.g., heater, steam \\ turbine), all with \\ fixed efficiencies \\ \end{tabular} \\ \hline
[14] & energy system & EnergyPLAN [45] & annual chemical biomass potential & Denmark & (wind, photovoltaic, wave, CHP, power plants), biogas purification \\ \hline
[46] & energy system & Sifre & \
\begin{tabular}{c} annual energy \\ potential of manure \\ and straw \\ \end{tabular} &
\begin{tabular}{c} Danish \\ municipality \\ \end{tabular} & - \\ \hline
[47] & energy system & TIMES &
\begin{tabular}{c} annual energy \\ potential of \\ degradable feedstock \\ \end{tabular} & Ireland & - \\ \hline
[16] &
\begin{tabular}{c} regional \\ potential \\ \end{tabular} & - & electrical energy potential of manure & Northwestern & - \\ \hline
[56] & \begin{tabular}{c} regional \\ potential \\ \end{tabular} & - & \
\begin{tabular}{c} sectional biogas \\ potential of manure \\ (cattle, pigs, sheep, \\ poultry) \\ \end{tabular} & Greece &
\begin{tabular}{c} chronological sequence since \\ 1970; contemplation of regional \\ gas grid \\ \end{tabular} \\ \hline
[57] & \begin{tabular}{c} regional \\ potential \\ \end{tabular} & - & \
\begin{tabular}{c} time-dependent \\ (seasons) biogas \\ potential of \\ agricultural residues \\ and municipal waste \\ \end{tabular} & Croatia &
\begin{tabular}{c} residue-to-product ratios, \\ sustainable removal rates \\ \end{tabular} \\ \hline
[58] & \begin{tabular}{c} regional \\ potential \\ \end{tabular} & - & \
\begin{tabular}{c} methane potential of \\ manure, grass silage, \\ municipal waste \\ \end{tabular} & Finland &
\begin{tabular}{c} Maximum feasible use of \\ regional feedstock due to \\ 30-day HRT; optimizing \\ GHG emissions \\ \end{tabular} \\ \hline
[59] & \
\begin{tabular}{c} regional \\ potential \\ \end{tabular} & - &
\begin{tabular}{c} municipal waste, \\ sludge, manure, silage \\ and crop residues \\ \end{tabular} & Finland & optimizing biogas plant placing \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Biogas top-down modeling (energy systems, regional impact, greenhouse gas (GHG) emission).