Assessment of modular biorefineries with economic, environmental, and safety considerations

Modular biorefineries correspond to prefabricated units that are assembled on-site and mounted on a steel structure or shipped from the manufacturer. Although the large-capacity biorefineries have typically been stick-built (where the major units of the biorefineries are constructed and assembled on site), there is a growing attention to modular biorefineries to address the needs for distributed manufacturing, resilience, and flexibility. Therefore, it is important to assess modular biorefineries in comparison with the conventional stick-built plants. This chapter provides an assessment of modular biorefineries while focusing on the economic, environmental, and safety objectives. A multicriteria assessment approach is adopted whereby simulation and techno-economic analysis are first carried out to identify a base case for both the modular option and the stick-built option. The environmental metrics are assessed via life cycle analysis. For the safety objective, the relative risk based on the Hazardous Process Stream Index (HPSI) is employed. The HPSI is based on five indicators pertaining to pressure, density, molar flowrate, heat of combustion, and flash point. A case study is solved on methanol manufacture from municipal solid waste. Two design options were considered: a single stick-built plant which produces 7000 t/yr and alternative design encompassing seven trains of modular plants each producing 1000 t/year. The results show that for the case study, the stick-built plants have an economic advantage while the modular units have superior performance in terms of environmental and safety objectives.