Development of a fuzzy optimization methodology for the systematic design of a microalgal multifunctional bioenergy system

The sole production of biofuels from microalgae poses economic challenges. Hence, the simultaneous production of various bioenergy and biochemical as co-products with algal biofuels makes it economically feasible. In order to synthesize an integrated design of multiple product system using microalgal feedstock, the concept of microalgal multifunctional bioenergy system (MMBS) was proposed. This dissertation focused on the development of a fuzzy optimization methodology for the systematic design of an MMBS with varying design objectives. Three thematic issues were presented in the conceptual design of an MMBS: 1) multi-criteria evaluation of varying cultivation systems, 2) multi-objective performance evaluation of cultivation systems in an MMBS, and 3) emphasis in the reduction of carbon footprint. In addressing issue 1, a stochastic analytic hierarchy process decision framework was established in selecting a suitable cultivation system for the sustainable production of biofuels. In addressing issue 2, two fuzzy linear programming (FLP) model were developed to assess the optimal performance of varying cultivation system in an MMBS and to design an algal polygeneration supply-chain across multiple regions. In addressing issue 3, a fuzzy mixed-integer linear programming (FMILP) model was established in selecting the optimal thermochemical process for the MMBS for negative carbon emission and a fuzzy fractional programming (FFP) model was developed to simultaneously design an MMBS given a carbon footprint allocation dictated by the customer. The results showed that flat-panel photobioreactor and the raceway pond were the preferred cultivation system for conservative (risk-averse) scenarios and optimistic (risk-inclined) scenarios, respectively. Furthermore, a conservative scenario in selecting a cultivation system together with slow pyrolysis was preferred for the optimal performance of the MMBS. Future work would involve the design of an MMBS producing high-valued products such as algal meals and nutraceuticals together with the algal biofuels as co-product