Toward a sustainable economic production quantity model employing triple bottom line strategy: Uncertain multi-objective optimization with lost sales and full back-order

The triple bottom line (TBL) strategy has provided the manufacturers with optimized production systems to achieve their economic, environmental, and social goals simultaneously. This paper presents a multi-objective mixed-integer programming model for the sustainable economic production quantity (S-EPQ) based on the TBL strategy. The model is to optimize the total profits, environmental emissions of manufacturing activities, and the turnover cost of the workers, which leads to keeping a sustainable number of workers as the social factor based on the working hours. According to numerous uncertain factors in the production process, demand uncertainty and the possibility of shortage have been considered including lost sales and full back-order. Due to the NP-hardness of the problem, Particle Swarm Optimization (PSO) algorithm is employed to find the optimal solutions and make the operational decisions of the production system. To prove the applicability of the proposed sustainable production system, a case study was conducted in the dairy industry of Iran. Moreover, an extensive analysis was done to evaluate the performance of the proposed multi-objective optimization model and heuristic solutions, and finally, some managerial insights were carried out for manufacturers of the dairy industry respecting the challenge of TBL.