Italian substantial energy dependency has fostered research and development on renewable-fuelled power plants. Among these fuels, woody biomasses guarantee environmental, economic and social benefits, in terms of local promotion for rural population and the subsequent cost reduction per unit of energy produced. However, significant fixed costs still compromise the spreading of these plants: for this reason, during the design stage, particular care will have to be taken to size the plant, minimizing both total costs and environmental impacts. In order to avoid an expensive over-sizing of the biomass plant, we will consider in this issue the case of a mixed installation fed by both traditional fossil fuel and woody biomass. Then we will introduce a detailed model to size this plant, minimizing both variable operating costs and fixed investment costs. Utilizing this algorithm on some of the major Italian cities, we will analyze the most significant results and, by means of a sensitivity analysis, the influence of the external conditions over them.
