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.

近年来，在全球范围内，可再生能源的发展令人印象深刻。这产生了有关生产过程，公民习惯，工业投资和消费者决定的变化。在这种情况下，政策制定者发挥了关键作用。补贴能够确定特定市场的发展。沼气市场遍布全球，而沼气市场集中在某些地区。可以将绿色气体用作车辆燃料，也可以将其注入气网，但也可以燃烧以进行热电联产。

本工作提出了对现有沼气厂的技术经济分析。尤其是，分析着重于两个可能的战略计划之间的比较，以便确定哪个计划在获利方面是最好的：第一个计划是扩建工厂以将沼气升级为沼气，而第二个计划是在工厂建成后按计划继续生产沼气。

本文提出了现金流量折现法（DCF），而净现值（NPV）是主要的指标。一250 m ³使用变压吸附（PSA）技术分析了位于意大利的/ h生物甲烷装置。结果表明，使用废粉煤灰合成的沸石对环境产生了积极影响，并且仅在某些情况下验证了盈利能力。但是，它们仅限于新的沼气厂的建设，而现有沼气厂的升级始终是无利可图的。盈亏平衡点（BEP）分析量化了沼气和沼气补贴的价值，以此可以实现盈利。生物甲烷可为循环经济模型的发展做出贡献，而可持续性目标仅在某些情况下才能实现。