A new concept for upgrading distributed co-generation plants to quad-generation plants, which combine the production of power, heating, cooling and synthetic natural gas (SNG), is designed and analyzed. Five cases with SNG production ranging from 0% to 100% of total energy outputs are designed to simulate different modes of operation. The quad-generation system is simulated using ASPEN PLUS and described by simulating different portions of the system. This paper also describes the new process, which is of particular interest for improving the total first law efficiency. With this system, It is possible to increase the efficiency of natural resource utilization, minimize the environmental impact in distributed generation, and, by providing flexible operation, better support the integration of intermittent renewables such as wind power. Straw is used as a biomass feedstock for this simulation. The net energy efficiency is used to evaluate the performance of the quad-generation system. The results show that the most efficient case of the proposed system is providing 89.8% net energy efficiency, which is almost 7.6% higher than the lowest efficient case. Based on the flowsheet simulation, this energy assessment compares the proposed quad-generation system to the existing district heating system. (C) 2015 Elsevier Ltd. All rights reserved.