Biofuel is one of the alternatives transportation fuel to substitute petroleum in the United States. Fast pyrolysis, as one of the most promising thermochemical based advanced biofuel production techniques, has been brought to the forefront of biofuel industry. With limited information about the manufacturing of fast pyrolysis units, a thorough understanding of stakeholders' requirements is timely and necessary. This study develops a comprehensive analysis of stakeholders' requirements. Subject matter experts were interviewed to rank, review, and evaluate a set of requirements for a variety of fast pyrolysis unit sizes. The requirements with the evaluations were then used to determine the most effective unit size. The analysis showed that the smallest unit size (process an average of 50 tons biomass per day) is the best alternative based on 50% of the high-prioritized requirements. However, 37.5% of the high-prioritized requirements recommended the unit which process at least 2000 tons per day as the best alternative.