A Multi-Criteria Decision Analysis (MCDA) approach was designed and used to evaluate different Fast Pyrolysis Unit (FPU) sizes. The MCDA approach is implemented via two models: Excel worksheet and automated model via Logical Decision® software. The proposed MCDA approach is an integration of the Pugh Concept Selection Matrix, Weighting Sum Method (WSM), and sensitivity analysis using Logical Decision® software. The data for the problem was collected from ten Subject Matter Experts (SMEs) using Pugh Matrix. In addition, two other integrated MCDA approaches were used to solve the same problem. The first approach integrated the Pugh Matrix and WSM. The second approach integrated the Pugh Matrix and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The designed framework is presented to identify Biofuel Production Stakeholders (BPS), their perspectives, and their requirements. The small FPU was found to be the best alternative using the three approaches. Furthermore, all these approaches allowed ranking of different alternatives based on the five perspectives of manufacturing biofuel production units: economic, environmental, technical, legal, and social perspectives. These five perspectives rely on 18 requirements that were frequently mentioned in previous research. The use of each approach gave different insight about the problem which could help decision-makers to understand the problem better and discuss the alternatives in depth. Sensitivity analysis suggested that the medium FPU is the best alternative in specific conditions under the perspectives-level analysis. On the other hand, it was suggested that the large FPU is the best alternative under specific conditions at the requirements-level analysis. An interesting finding from this research is that from the environmental perspective the medium FPU is recommended as the best alternative instead of the small FPU. In addition, the TOPSIS analysis provided the theoretical positive and negative ideal solutions to help the decision makers gain a better perception of the optimal design of FPUs. Moreover, WSM was found to be the simplest MCDA tool to use. In contrast, TOPSIS was found to be a more complicated tool yet similar to WSM both could not examine result robustness. The proposed approach provided the result robustness limitations.