Sustainable smart pharmaceutical third-party logistics supply chain with controllable waste and wastewater treatment

Pharmaceutical and personal care products are emerging environmental contaminants, largely originating from household waste streams. Therefore, integrating the circular economy principle into pharmaceutical supply chains with waste reduction by enabling the safe collection, screening, and redistribution of unused medicines to those in need. In this study, blockchain-enabled drug recycling to enhance trust, visibility, data integrity, and its integration with green pharmaceutical supply chains under third-party logistics (3PL) coordination remain limited. The model incorporates drug price indices, demand-dependent sales, green investment decisions, pharmaceutical waste management, and wastewater treatment cost. Due to the nonlinear and combinatorial nature of the problem, a genetic algorithm (GA) is developed with customized encoding, fitness evaluation, selection, crossover, and mutation operators to determine optimal logistics under sustainability constraints. Numerical experiments demonstrate that the GA converges rapidly to near-optimal solutions, reducing total system cost and environmental impacts compared to non-coordinated or non-blockchain scenarios. Sensitivity analysis on demand, price index, and green investment parameters confirms the robustness of the solution. The study establishes that coordinated green investments, enabled by blockchain traceability and GA-based optimization, improve both economic and environmental performance, providing a decision-support tool for designing sustainable, transparent, and resilient pharmaceutical supply chains aligned with circular economy objectives.