A biomass-based trigeneration system produces heat, power and cooling energy simultaneously. To synthesize a biomass-based trigeneration system, decision makers are required to consider a wide range of technologies based on various factors (e.g., capital investment, operating cost, availability and reliability of the technologies, etc.). In addition, both short-term and long-term uncertainties that may arise during the course of operations should also be taken into consideration. If not considered at the synthesis stage, uncertainties would prevent the designed energy system from meeting the required energy demands and cause possible bottlenecks during operation. With such consideration, not all available technologies are economically and operationally sensible. Thus, it is essential to develop a systematic approach to synthesize a biomass-based trigeneration system with consideration of uncertainties. In this work, a multiperiod optimization approach for the systematic synthesis of a biomass-based trigeneration system with variations in raw material supply and corresponding energy demand is presented. Following the concept of multiperiod optimization approach, the fraction of occurrence for each biomass supply and energy demand scenario is included. Meanwhile, the maximum capacities of each technology that can operate in all scenarios are determined. In addition, selection of design capacities based on available sizes in the market is also performed simultaneously. To illustrate the proposed approach, a trigeneration system with palm-based biomass as feedstock is solved.