Trigeneration systems produce heat, power and cooling simultaneously from a single fuel source. With such efficient use of fuel, installing trigeneration systems on-site would be beneficial as it reduces the requirement of external power and fuel, reduces emissions, and improves local power reliability. On the other hand, trigeneration systems need to have a reliable network of component process units, since the high level of integration increases the likelihood of cascading failures. Each unit may not always be available to function because it may require preventive or corrective maintenance during the course of operations. Traditionally, this issue is handled by installing additional process units based on heuristics. This approach, however, may not be able to address complex decisions on whether to purchase a single additional unit with larger capacity or multiple smaller capacity units. Additionally, the decision becomes increasingly complex when seasonal variations in operations are considered. If not addressed appropriately, such decisions may result in excessive capital and/or maintenance costs. To address these issues, this work presents a systematic procedure for the grassroots design of a trigeneration system considering equipment redundancy for variations in raw material and energy demand. To illustrate the proposed approach, a simple case study on designing a grassroots steam turbine configuration for a biomass-based trigeneration system (BTS) is presented.