# Sustainable Italian Cities: The Added Value of Biomethane from Organic Waste
## 4 Results
### Calculation of Potential Biomethane Profits--Baseline Scenario  
The decisional criteria used in this work were as follows:  
* A plant was built only if economic feasibility was reached, according to plant size. As demonstrated in Figure 3, a 200 kt plant was the minimum size. * The pant size was defined according to Table 8, with allowance for a slight approximation by excess. * The plant size varied from 200 kt to 500 kt, in multiples of 50 kt. * The NPV obtained in the baseline scenario was considered the economic profit of reference. Table 9 presents the number of biomethane plants, the definition of the plant size, and the calculation of the economic profit for each municipality. For example, there were four 500 m\({}^{3}\)/h plants and one 400 m\({}^{3}\)/h plant in Rome in the \"As Is\" scenario, and eight 500 m\({}^{3}\)/h plants constructed in two \"To Be\" scenarios. The main results are reported in Table 10. Fifteen municipalities could achieve profit in an \"As Is\" scenario characterized by eight 500 m\({}^{3}\)/h plants; two 250 m\({}^{3}\)/h plants; and one 200, 300, 350, 400, and 450 m\({}^{3}\)/h plant. This determined a biomethane productivity equal to 6200 m\({}^{3}\)/h; considering an operational period of 8000 h, the production of biomethane was equal to 49.6 million m\({}^{3}\) (approximately 5% of the amount supported by incentives (1100 million m\({}^{3}\))--see Section 3.3). The advantages of biomethane could be explained from an environmental perspective (about 78.1 thousand tons of CO\({}_{2}\).eq were avoided annually, and, consequently, 1.6 million tons of CO\({}_{2}\).eq were avoided over a period of 20 years) and an economic perspective (as the value of profits were 85 million \(\mathfrak{C}\) during the project lifetime). The results of this work underline that biomethane plants support the attainment of several goals, as follows:  
* The OFMSW produced by the citizens can pose a challenge to the ecosystem. In fact, the incorrect management of these flows towards landfills or long-distance transport to a limited number of plants increases GHG emissions. Thus, the biogas-biomethane chain reduces environmental damage [95; 96]. * The biomethane obtained by OFMSW transforms this waste into a resource. Several economic opportunities are generated and the profitability of plants undertaking this processing can reduce the tax bills paid by citizens. In fact, economic feasibility is also obtained when net revenues are reduced in the treatment of the OFMSW [27; 61]. The final goal is to stimulate the citizens \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Scenarios** & **As Is** & **To Be—65\%SC** & \
\begin{tabular}{c} **To Be—65\%SC** \\ **40\% OFMSW** \\ \end{tabular} &
\begin{tabular}{c} **To Be—110** \\ **kg/Inhabitant** \\ \end{tabular} \\ \hline Torino & 500 & 773 & 1043 & 915 \\ Milano & 1310 & 1478 & 1656 & 1394 \\ Verona & 236 & 280 & 338 & 265 \\ Venezia & 337 & 389 & 406 & 270 \\ Padova & 248 & 295 & 304 & 216 \\ Trieste & 80 & 132 & 229 & 211 \\ Genova & 167 & 330 & 700 & 602 \\ Bologna & 214 & 305 & 544 & 401 \\ Firenze & 436 & 584 & 586 & 394 \\ Roma & 2392 & 3753 & 4117 & 2963 \\ Napoli & 544 & 1205 & 1266 & 1001 \\ Bari & 153 & 276 & 466 & 334 \\ Palermo & 79 & 726 & 846 & 695 \\ Messina & 20 & 116 & 277 & 244 \\ Catania & 42 & 271 & 532 & 323 \\ Total & 500 & 773 & 1043 & 915 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Potential biomethane productivity (m\({}^{3}\)/h). to separate waste in order to lower their waste collection bill. Should this occur, the revenues received by the municipalities would be reduced, and, consequently, the payments made by the municipalities to the OFMSW treatment plants would also be reduced. * Biomethane produced by OFMSW increases the share of renewable energy in the transport sector. This goal is urgent.