Optimal planning and site selection for distributed multiproduct biorefineries involving economic, environmental and social objectives

Biorefineries appear to be a viable solution to replace traditional fossil fuel refineries, but their implementation requires the exploration of several aspects, including feedstock selection, processing routes, products, harvesting sites, processing and markets, as well as numerous other sustainability criteria. The optimal solution to these problems is not immediately obvious. Therefore, this study presents an optimization model to design and plan sustainable biorefinery supply chains that considers numerous relevant issues. These issues include the multiple available biomass feedstocks at various harvesting sites, the availability and seasonality of biomass resources, different potential geographical locations for processing plants that produce multiple products using diverse production technologies, economies of scale for the production technologies, demands and prices of multiple products in each market, locations of storage facilities and a number of transportation modes between the supply chain components. Sustainability considerations are incorporated into the proposed model by including simultaneous economic, environmental and social performance data in the evaluation of the supply chain designs. The problem was formulated as a multi-objective, multi-period, mixed-integer linear program that seeks to maximize the profit of the supply chain, minimize its environmental impact and maximize the number of jobs generated by its implementation. The environmental impact was measured by the Eco-indicator99 according to the life-cycle assessment technique, and the social objective was quantified by the number of jobs generated. The Pareto-optimal solutions were obtained using the ε-constraint method. To illustrate the capabilities of the proposed multi-site system model, a case study was presented that addresses the optimal design and planning of a biorefinery supply chain to fulfill the expected ethanol and biodiesel demands in Mexico. The results indicate that cost-effective and sustainable solutions can be obtained that satisfy Mexican demand by choosing feedstocks that are available year-round and do not significantly adversely impact the environment. Furthermore, the number of jobs generated by implementing the biorefinery supply chain would have a significant social impact.