A techno-economic assessment of biogas upgrading in a developed market

The development of renewable energies was impressive in recent years on a global scale. This produced changes regarding production processes, citizens' habits, industrial investments and consumer decisions. In this context, the policy-maker played a crucial role. The subsidies are able to determine the development of a specific market. Biogas market spread globally, while biomethane market concentrated in some territories. Green gas can be used as vehicle fuel or injected into the gas grid but also burnt for co-generation. The present work proposes a techno-economic analysis for an existing biogas plant. In particular, the analysis was focused on the comparison between two possible strategic plans, in order to establish which one was the best in terms of profitability: the first one is the expansion of the plant to upgrade biogas to biomethane, whereas the second one is to continue the production of biogas as planned when the plant was constructed. The Discounted Cash Flow (DCF) method was proposed in this paper, and the Net Present Value (NPV) is the main index used. One 250 m3/h biomethane plant located in Italy using pressure swing adsorption (PSA) technique is analysed. The results demonstrated the positive environmental impact deriving from the use of zeolites synthesized from spent fly ash and the profitability is verified only in some scenarios. However, they are limited only to the construction of new biomethane plants, while the upgrading of existing biogas plants are always unprofitable. A Break-Even Point (BEP) analysis quantifies the value of subsidies of biogas and biomethane by which the profitability could be reached. Biomethane can contribute to the development of circular economy models, while the sustainability targets are achieved only in some scenarios.