# Sustainable Italian Cities: The Added Value of Biomethane from Organic Waste
## 1 Introduction
In supporting this shift, however, government initiatives play a key role. Policies vary significantly in their tactics to promote the green energy transition in times of crisis, according to the specific aim pursued (i.e., profit, jobs, or EU targets) [32; 33]. Sweden demonstrates best practice among member states in the development of green fuels [34], and some authors have focused their attention on the relationship between achieving regulatory compliance and improving biofuel sustainability [35]. In Sweden, public organizations make a significant contribution to the shift--some municipalities use environmentally friendly cars, Sweden'ia steers via a taxi queuing system, and Stockholm Public Transport procures biogas, matching the production of municipal wastewater treatment plants [19]. The development of CE models is verified by the recovery of some wastes that are perceived as resources and not only issues. Agricultural residues [36] and organic waste [37] are two such examples. Figure 1: Map of the biogas–biomethane chain. Adapted from the literature [27]. Furthermore, some researchers have demonstrated that, while OFMSW management is complex, OFMSW can be valorized through transformation into biomethane [38]. The co-digestion of multiple feedstocks is technically feasible, and the best method for enhancing biogas production is to combine the potential results of biomethane with continuous AD testing [39]. Energy crops present a significant methane potential, and they have been widely used in biogas plants; however, their use may determine a change in land use, which would penalize agriculture [40]. The use of residual biomass achieves a better environmental performance than the use of dedicated biomass [41]. Within this context, Italy represents an interesting case study, because of its developed biogas market and its undeveloped biomethane market [27; 42]. Years ago, the Italian Biogas Consortium elaborated a roadmap for the production of approximately 8 billion Nm3/year biomethane [43], and the Italian Biomethane Decree (signed 2 March 2018) aims at promoting the production of biomethane in order to increase the share of green fuels in the Italian transportation sector [44]. The novelty of this work is based on the following assumptions: (i) biomethane is a promising renewable resource that may support decarbonization in the transport sector; (ii) single cities can promote CE models to increase the sustainability of the energy sector; (iii) quantitative analyses may provide valuable information to investors and policymakers; (iv) Italy is a paradoxical case study, as it has all of the available input for a biomethane market, but the development of this market has not yet occurred; and (v) biomethane supports the interaction between renewable energy and waste management. Focusing on 15 Italian municipalities, the research uses both economic and environmental analyses to demonstrate the added value of biomethane from organic waste. The paper presents a comparative analysis of four scenarios, including the current one. Starting with the amount of OFMSW produced in each geographic entity, a strategic analysis is introduced to define the optimal plant size in order to manage these flows. The production decision is necessarily long-term, because the lifetime of a biomethane plant is 20 years [27; 45], and the interaction between renewable energy and waste management seeks to achieve a CE model. Subsequently, an economic analysis based on discounted cash flow (DCF) is proposed, and the index of the reference is the net present value (NPV). Baseline and alternative case studies are constructed on the basis of the defined critical variables. The value of the subsidy is fixed by decree through the Certificates of Emission of Biofuel in Consumption (CIC) for the first 10 years, but their value is not known for the last 10 years.