A three-echelon sustainable supply chain model for growing items with climate effects, carbon emissions, and delayed payments

Growing-item supply chains, such as those for poultry and livestock, face increasing economic and environmental pressures resulting from carbon emissions, waste generation, and climate variability. This study develops a new economic order quantity model tailored for growing items within a three-echelon supply chain consisting of a farm, a processor, and a retailer. The model integrates circular economy practices through a circulatory index that captures the influence of feed recycling and waste repurposing on demand, incorporates carbon-reduction policies such as taxes and cap-and-trade, and embeds climate-dependent factors that affect both growth and product quality. The framework also includes delayed payments through a two-level trade credit mechanism to improve financial coordination. A climate-adjusted logistic growth function is employed to represent biological growth, while emissions from feeding, processing, and transportation are included in the cost structure. The objective is to maximize the expected total profit per unit time while reducing environmental impact, supporting responsible consumption, production, and climate-action goals. Numerical experiments show that improvements in the circulatory index increase demand and profitability, whereas higher temperatures reduce profits due to slower growth and greater defects. Sensitivity analysis highlights feeding costs and climate variables as the most influential parameters. The results provide practical insights for managers seeking to enhance profitability while transitioning to cleaner and more resilient supply chain practices.