# Comparative Analysis of Machine Learning Methods for Predicting Energy Recovery from Waste
## 2 Materials and Methods  
Three machine learning methods, namely ElasticNet, Decision Trees, and Neural Network, were used to model energy recovery from waste. The data on energy recovery from waste for 22 EU countries available in Eurostat (the EU statistical office) database (Eurostat, 2022) are presented in Table 1. Economic and environmental indicators were used as input data for the models. The data were obtained from the Eurostat database [21]and are presented in Table 2. The data for 2013-2020 for 25 European countries were used. The criteria for country selection were based on the availability of comprehensive and reliable data on waste management and energy recovery, as well as the desire to represent a diverse range of waste management practices and energy recovery capabilities across the European Union. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Recovery–Energy Recovery** & **Mean** & **St** & **Min** & **Max** & **Share of WtE in Global Waste Production [\%]** \\ \hline Belgium & 207.78 & 62.79 & 173.00 & 356.00 & 5.81 \\ \hline Bulgaria & 15.11 & 6.97 & 7.00 & 30.00 & 0.56 \\ \hline Czechia & 68.72 & 12.19 & 55.00 & 85.00 & 3.59 \\ \hline Denmark & 421.11 & 15.58 & 397.00 & 447.00 & 17.51 \\ \hline Germany & 172.94 & 22.28 & 142.00 & 193.00 & 11.26 \\ \hline Estonia & 169.94 & 8.44 & 163.00 & 185.00 & 2.05 \\ \hline Greece & 5.06 & 2.60 & 2.00 & 8.00 & 1.39 \\ \hline Spain & 53.44 & 4.36 & 46.00 & 60.00 & 3.26 \\ \hline France & 174.44 & 3.84 & 170.00 & 180.00 & 7.24 \\ \hline Croatia & 0.28 & 0.44 & 0.00 & 1.00 & 3.49 \\ \hline Italy & 85.78 & 17.28 & 49.00 & 99.00 & 4.62 \\ \hline Cyprus & 4.06 & 3.23 & 0.00 & 9.00 & 8.35 \\ \hline Latvia & 10.00 & 3.54 & 5.00 & 15.00 & 6.29 \\ \hline Lithuania & 70.17 & 29.61 & 31.00 & 125.00 & 6.92 \\ \hline Luxembourg & 327.22 & 58.89 & 237.00 & 379.00 & 3.25 \\ \hline Hungary & 49.50 & 8.67 & 34.00 & 62.00 & 7.64 \\ \hline Malta & 0.78 & 0.97 & 0.00 & 2.00 & 0 \\ \hline Netherlands & 225.89 & 15.89 & 206.00 & 250.00 & 7.53 \\ \hline Austria & 229.11 & 31.29 & 202.00 & 298.00 & 7.21 \\ \hline Poland & 55.11 & 22.35 & 15.00 & 74.00 & 2.15 \\ \hline Portugal & 97.72 & 6.63 & 91.00 & 110.00 & 7.15 \\ \hline Romania & 10.56 & 3.64 & 5.00 & 15.00 & 1.38 \\ \hline Slovenia & 46.94 & 29.28 & 1.00 & 82.00 & 2.54 \\ \hline Slovakia & 32.11 & 4.37 & 23.00 & 36.00 & 4.91 \\ \hline Finland & 285.83 & 47.49 & 209.00 & 349.00 & 5.37 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Energy recovery (in kg per capita) for selected European Union countries in the years 2013–2021 [22]. \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline  & **Unit** & **Mean** & **St. Dev** & **Min** & **Max** & **Source** \\ \hline Electricity prices by type of user (EPTU) & kWh & 0.177 & 0.055 & 0.083 & 0.319 & [23] \\ Energy productivity (EP) & Eur/kgOE & 6.728 & 2.883 & 2.178 & 17,020 & [24] \\ Final energy consumption (FEC) & Mtoe & 36.940 & 51.050 & 0.500 & 221.000 & [25] \\ Gross domestic product at market prices & Eur/capita & 27,259.556 & 19,048.670 & 5790.000 & 113,050.000 & [26] \\ (GDPMP) & \% & 36.636 & 15.395 & 9.100 & 70.300 & [27] \\ Recycling rate of municipal waste (RRMW) & Domestic material consumption per capita & t/capita & 16.698 & 7.632 & 7.722 & 48.605 & [28] \\ Environmental tax revenues (ETR) & \% & 7.193 & 1.761 & 3.610 & 11.750 & [29] \\ Share of energy from renewable sources (SERS) & \% & 20.618 & 9.908 & 3.494 & 43.939 & [30] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Selected key indicators in various environmental and energy sectors in selected countries of the European Union for the period 2013–2022 [21]. The following input data were used:  
* Electricity prices by type of user refer to different electricity prices for different categories of users. * Energy productivity measures the efficiency with which the economy or system converts energy into productive activity, i.e., how much economic value is generated per unit of energy used. * Final energy consumption refers to the amount of energy consumed by final users.