VIKOR - P-graph Method for Optimal Synthesis of Philippine Agricultural Waste-Based Sustainable Integrated Biorefinery

Abstract

A sustainable integrated biorefinery (SIBR) is a biomass processing facility that converts agricultural wastes or residues into a wide range of valuable products where both economic sustainability and environmental sustainability are optimized. This work proposed a hybrid method that incorporates Vlsekriterijumska Optimizacija I Kompromisno Resenje (VIKOR), a widely used multi-criteria decision-making (MCDM) tool with the P-graph (process-graph) framework. The proposed VIKOR - P-graph model can (i) generate a set of combinatorically feasible solutions, and (ii) rank the solution sets using VIKOR method, simultaneously in the same P-graph model. In other words, all the drawbacks attributed to the sequential optimization methods can, therefore, be avoided. To demonstrate the effectiveness of the proposed hybrid methodology, a case study in the Philippines is presented in this paper. The hybrid P-graph model generated a total of 7 feasible solutions with different configuration for the SIBR based on the overall profit (i.e., economic goal) and carbon emissions (i.e., environmental goal). Results show that the best compromised solution can be obtained when majority (70 %) of the rice husk is used to produce bioethanol, where the required power is supplied by combusting the remaining rice husk and by importing external power. It offers an hourly profit of 161 $/h with a lower (~38.6 %) carbon emissions as compared to the most profitable option (3.504 tCO2-eq/h). This research is essentially a guide for policymakers to make informed decisions that can maximise the benefits of SIBR on a national scale.