Techno-economic analysis of biogas production and use scenarios in a small island energy system

This paper investigates the economic, energy and environmental benefits given by the installation of an anaerobic digester in a small island. Particularly, the island of Procida is chosen as a case study where the production of organic fraction of municipal solid waste is equal to 2477 t/year. Three scenarios are hypothesized for the use of the locally produced biogas, namely: (i) upgrading of biogas and injection into the gas grid for the residential sector (replacing 21% of natural gas consumption); (ii) upgrading and use in transport sector (covering waste trucks, non-organic waste ferry and shuttle buses consumptions); (iii) use of biogas in a Combined Heat and Power (CHP) plant (covering 4% of electricity consumptions). The scenarios are analysed and compared in economic, emissions and energy terms. Although the biogas covers just a small part of consumption, it can still provide a relevant contribution to the island energy system by diversifying the energy mix while increasing the renewable energy sources penetration and also increasing the independence. The results show advantageous payback time (4–5 years), and this is mainly due to the significant savings in the maritime transport and the partial avoidance of the waste disposal on the mainland the incentives.