In this paper, a biogas fuelled power generation system is considered. The system is based on a molten carbonate fuel cell (MCFC) stack integrated with a micro gas turbine for electricity generation, coupled with a pressure swing absorption system (PSA) for hydrogen production. The aim of this work is the optimal design of the system plant considering thermodynamic and economic objective functions. Optimization is performed by modifying the design parameters characterizing the operation of the fuel cell, the reformer and the micro-turbine. The corresponding costs and performances are obtained using a model developed at component level. Pinch analysis technique and a general heat exchanger network are used in order to select the optimal configuration of the heat exchangers. As a result, the Pareto front relating maximum efficiencies and minimum unit cost of electricity is obtained. The design corresponding with minimum cost of electricity, 0.036 (sic)/kWh, is characterized by an electrical efficiency of about 0.46. The design corresponding with maximum efficiency, about 0.62, is characterized by a unit cost of electricity of 0.055 (sic)/kWh. In the last part of the paper the effects produced by single variation of the design variables on unit cost of electricity and electrical efficiency are discussed. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.