# Sustainable Italian Cities: The Added Value of Biomethane from Organic Waste
## 4 Results
### The Calculation of Potential Biomethane Productivity  
Following the economic descriptions, this section provides details on potential biomethane productivity. Table 7 outlines the potential amount of the OFMSW to be treated, according to the four scenarios defined in Section 3.2.  
As expected, the amount of OFMSW changed significantly across the four scenarios. Certainly, the values proposed in the \"To Be\" scenarios were greater than those of the \"As Is\" scenario (equal to 721 ktons). This means that a substantial amount of waste became unsorted waste and some entered landfills, violating the good practices of the waste hierarchy. In this way, these municipalities did not maximize the recycled/recovered quantity. Only Milano, Verona, Venezia, and Padova had a recycling rate greater than 55%; at the same time, this value was lower than 12% in Palermo, Messina, and Catania (see Table 2). For this reason, two scenarios, \"To Be--65%SC\" and \"To Be--65%SC 40%OFMSW,\" were constructed. The target recycling rate of 65% was fixed, and an increase in the sorted waste determined an increase of all of the components in this mix (e.g., the OFMSW, paper, glass, and plastic). The total amount of OFMSW in \"To Be--65%SC\" was 1164 ktons, which was lower than 1420 ktons (\"To Be--65%SC 40%OFMSW\"). In fact, the weight of the OFMSW in the collected waste mix in the \"As Is\" scenario was lower than 40% in all of the municipalities, varying from 17% in Messina to 39% in Padova. It was not possible to compare these two scenarios from an environmental perspective. However, the same cannot be said for the \"To Be--110 kg/inhabitant\" scenario (equal to 1091 ktons). In fact, another good practice of waste management is reducing generated waste. A defined value (in this case 110 kg/inhabitant) could counter this approach.  
According to Equation (1), it was possible to calculate the potential biomethane productivity expressed in m\({}^{3}\) per hour (Table 8). In this way, the value could be interpreted as the biomethane plant size.  
\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 & 53,312 & 82,480 & 111,213 & 97,552 \\ Milano & 139,740 & 157,689 & 176,612 & 148,672 \\ Verona & 25,223 & 29,851 & 36,085 & 28,309 \\ Venezia & 35,904 & 41,480 & 43,316 & 28,810 \\ Padova & 26,460 & 31,518 & 32,393 & 23,081 \\ Trieste & 8570 & 14,075 & 24,467 & 22,466 \\ Genova & 17,802 & 35,196 & 74,695 & 64,196 \\ Bologna & 22,834 & 32,486 & 57,983 & 42,720 \\ Firenze & 46,518 & 62,339 & 62,549 & 42,049 \\ Roma & 255,161 & 400,301 & 439,194 & 316,084 \\ Napoli & 58,017 & 128,481 & 135,049 & 106,721 \\ Bari & 16,309 & 29,397 & 49,745 & 35,662 \\ Palermo & 8458 & 77,453 & 90,222 & 74,111 \\ Messina & 2139 & 12,388 & 29,495 & 26,066 \\ Catania & 4457 & 28,911 & 56,735 & 34,473 \\ \hline Total & 720,904 & 1,164,045 & 1,419,753 & 1,090,970 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Potential amount of the OFMSW conferred to biomethane plants (tons).