## 3 Results  
Horticultural producing areas acquired by the ISTAT database were deeply analyzed for the different provinces by providing a GIS map to show their territorial distribution. In detail, ISTAT data were used to localise, on a territorial level, the distribution of cultivated areas dedicated to horticultural production. By adopting the Jenks tool, available in the QGis software, the Sicilian provinces were grouped in three different classes in order to maximise the differences in the cultivated areas. As a result, the areas that showed the highest horticultural surface areas were the provinces of Palermo, Agrigento and Caltanissetta, as shown in Figure 2.  
Then, the horticultural cultivated areas were subdivided into horticultural open field crops and horticultural greenhouses (Table 1) by showing different distributions within the Sicilian provinces, as reported in Figure 3a,b. The distribution of the horticultural cultivated areas allows the identification of two different areas for horticultural production located in the south-west and in the south-east of the island, respectively, for open field crops and greenhouses. The second step was the analysis of the horticultural production, since the most productive areas could not correspond to the most cultivated areas. The next step was focussed on wholesale market localisation. After a direct interview with the regional coordinator of wholesales market activities, the Sicilian active wholesale markets were located within Sicily region by considering their GPS coordinates, and a GIS map was made as shown in Figure 4.  
Figure 2: Distribution of horticultural cultivated area within the Sicily region (ISTAT, from 2015 to 2019). In order to quantify wholesale market residues and waste production, firstly all the wholesale market data (i.e., production flows) were analysed based on the available database, and by using the GIS tool (i.e., Heatmap plugin) a heat map of their production was made (Figure 5). Figure 3: (**a**) Distribution of horticultural open field crop cultivated areas. (**b**) Distribution of horticultural greenhouse cultivated areas (ISTAT from 2015 to 2019). As reported in Figure 5, firstly (in orange) all the wholesale markets data were elaborated for the production of a heat map; then, among them, the wholesale markets with the biggest flow production were selected (in pink), and their data were elaborated by adopting again the heat map tool. An overlay of the two produced heat maps was carried out in order to show the high difference of flow production (Figure 5). Figure 4: Wholesale market localisation within Sicily region (data obtained by direct interviews). Figure 5: Wholesale markets heat map distribution based on their flow production. In detail, the largest and most important wholesale markets, sited in the provinces of Catania, Ragusa, and Palermo, were selected as a sample for carrying out a face-to-face survey analysis with the aim of estimating the quantity of FVWs. The surveyed data are summarised in Table 3 in order to define an average percentage of potential horticultural wastes in the period between 2015 and 2019. As shown in Figure 6, by considering all the horticultural products, the provinces of Syracuse, Ragusa, Agrigento, Catania, Palermo and Caltanissetta were highlighted as the most productive ones. Furthermore, the results of the analysis of the production of the three selected biggest wholesale markets confirmed the results obtained with the ISTAT database on the horticultural production by highlighting three different areas (Figure 6). The last step of the study was the computation of the potential biogas production by recycling FVWs. As reported in Table 3, the FVWs were computed, and by using Equation (1) the potential biogas was estimated to be about 7 million of Nm\({}^{3}\)[44]. In detail, as reported in Figure 7, the heat map with potential biogas production obtainable by the three selected wholesale markets was produced.