With more renewable introduction, distributed generation emerges to be important. Combining multiple utility outputs in a single unit, formally called 'polygeneration' is a good option using available local resources, say biomass. However, such plants are to be economically feasible and environmentally acceptable also for sustainable operation. In this paper, a step-by-step feasible sustainable system design of a polygeneration plant to deliver power, heating, cooling and fresh water is reported. It is simulated by Aspen Plus (R). The plant is optimized and assessed from thermodynamic, economic and environmental viewpoints. Results show that up to 20% of primary energy savings is possible by optimum process integration and 25 kt/y of CO2 emission may be reduced. Gasifier, combustion chamber and condenser destruct exergy mostly. Payback period of the plant is 6.66 years and fuel feed rate of the plant should be more than 20 t/d for a feasible sustainable operation. (C) 2015 Elsevier Ltd. All rights reserved.