## 4 Discussion  
Sicily and other southern Italian regions are well behind the rest of the country in terms of anaerobic digestion plants and the agro-energy chain in general [45]. The production potential of bio-methane in many parts of southern Italy is undeveloped and even unknown despite being potentially very high [46].  
Furthermore, there is a great number of agro-industrial processing plants which could provide large quantities of \"integrated biomasses\" like citrus pulp and olive pomace, the last being absolutely appropriate for producing advanced biofuels [32; 33; 34]. In this context of green energy management, the possibility to reduce the wastes obtained by the wholesale market of fruits and vegetables is also a concrete option.  
FWWs are produced in huge quantities by wholesale markets and represent an important category of residues that are difficult to dispose of because of their high perishability. They are easily degraded by the microbial bacteria with a speed dependent on the presence of mechanical damage or excessive ripening. This leads to significant environmental complications and high costs for fruit and vegetable markets both for disposal and for economic losses due to the lack of product sales. Anaerobic digestion may be the most appropriate technology for the disposal and energy valorisation of these residues [47].  
Therefore, it would be preferable that the future policies of development of the biomethane sector take into account the availability and distribution at a territorial level of other agro-industrial biomasses [48], in order to find the optimal location of new anaerobic digestion plants [42; 43; 44; 45; 46; 47; 48; 49].  
The amount of FVWs estimated to be sent to anaerobic digestion plants is just under 46 thousand tons of biomasses. This means that this biomass could make a net contribution  
Figure 7: Estimation of biogas availability.  
to the production of biomethane. However, there is a limit imposed by the Italian law about disposal and reuse. In particular, the by-products produced by the wholesale market are classified as \"waste\" (in accordance with art. n\({}^{\circ}\) 10 of Legislative Decree 205/2010 [50]) because the wholesale market is the final step of the chain before the sale: If the products are not suitable for sale, they are waste. Instead, they can be classified as \"by-products\" (in accordance with art. n\({}^{\circ}\) 12 of Legislative Decree 205/2010 [50]) if they are produced by a farm that sells to the wholesale market. So, if the anaerobic digestion plant is authorised only for the utilisation of by-products and if its manager wants to use digestate as an organic soil improv for agricultural soil, wholesale market FVWs cannot be used as feedstocks.  
This is nonsense because the product at the market does not undergo manipulation or alteration. It is the same product that is considered differently only because its holder (wholesale market or farmer) is different.  
If these biomasses were treated as by-products and not as wastes, producers would avoid landfill disposal costs and could only pay for the delivery to biogas plants. Even more, biogas plant owners might be willing to pay for having these biomasses. Therefore, a virtuous economic circle could be generated: From waste to by-product.