The study investigated problems of determining the lot size by considering sustainability and capital constraints for purchasing raw materials and taxes. By using the Sustainable EOQ (SEOQ) models that considered environmental aspects, the researchers also evaluated the capital constraints. The proposed models were used to minimize total inventory costs. In this study, there was a practical numerical analysis and sensitivity analysis to help decision-makers and policies on inventory problems. Finally, the experimental results showed that the proposed models were effectively used to solve the problems.

In selecting suppliers, one approach that can be used to solve this problem is Multi-Criteria Decision Making (MCDM). MCDM involves several criteria with both quantitative and qualitative assessments. This research attempts to solve the Green Supplier Selection (GSS) problem by using the integration of Analytical Hierarchy Process (AHP) and Multi-Objective Optimization On The Basis Of Ratio Analysis (MOORA). AHP is used as the weighting of the GSS criteria and sub-criteria. Furthermore, MOORA is used to rank the best suppliers. This research was conducted in the textile industry in Indonesia. Eight criteria and 15 sub-criteria GSS are used to select eight suppliers. The results show that the product price has the most excellent weight in supplier selection. In addition, the AHP-MOORA method can be used in solving GSS problems.