有鑑於全球資源逐漸缺乏，世界各國開始制訂環保相關法規，來規範產品的購買與製造。世界各大企業亦為了配合各國政府所訂定的相關法規，在採購產品以及製造產品時，都會符合所謂的綠色採購原則。在這種情況下，雖然企業可以使用回收品再利用，可是考慮到回收品無法完全回收，可再利用率或是可拆解率等，而造成回收品不足以滿足顧客需求。此時，就需搭配購買新品來滿足需求，以確保顧客滿意。
另一方面，現在有許多企業為了要提高市場佔有率、刺激市場的需求或是降低本身庫存的壓力，而考慮給予買方延遲付款的優惠以增加訂購量。這種優惠不但讓買方可以減少因購買貨品而造成存貨資金積壓的壓力，更可以因為提早在付款期限內出清，而賺取機會成本。但是買方如果沒辦法在信用交易期間賣完的話，又會產生額外的資金積壓所衍生的利息，這將造成無形的負擔。
本研究將對於回收品處理數量與另購新品之間的最佳經濟訂購批量進行探討。回收品會考慮到回收率且採立即付款方式，而新品則是在具有延遲付款機制下進行採購。在整合兩者模式後，求出回收品處理批量及新品的訂購批量，使得模式更接近現今市場交易方式。
藉由模式的探討以及敏感度分析，本研究得到因為參數與機會成本對訂購批量以及回收開始再處理的數量的影響情形。另外，由於環保議題的關係，現在有許多企業開始同時考慮新品與回收品，因此可以建議決策者在進行採購時，可以將機會成本對於新品與回收品之影響納入考量，並可以更謹慎考慮兩者之關係，而使得更能應用於現實情況。

Because the resources decrease ceaselessly, countries have started to regulate product’s purchasing and manufacturing to compensate environmental protection. Upon these regulations, enterprises have begun recycling products. Since recycling is unable to reuse the original material completely, recycled products cannot meet the customer’s demand solely. They must purchase new products to fulfill their need.
However, many enterprises want to increase the market share or lower stock level. They provide delay in payment to the customers to increase the order quantity. If buyers can sell all goods in a certain time period, they can accumulate revenue and earn interest. Otherwise, they will be charged higher interest.
This thesis discusses the optimal order quantity of new products and the processing quantity of recycled products. For the recycled products, the return rate is considered and payment is paid off immediately. The payment of purchasing new products can be offered a credit period. Finally, we confirm the order quantity of new products and the processing quantity of recycled products into a mathematical model.
Based on our models and through sensitivity analysis, this research finds the relationship between the order quantity of new products and processing quantity of recycled products according to the change of parameters. In addition, for enterprises which purchase new and recycled products simultaneously, we also provide managers the relationship of opportunity cost on the new and recycled products in the realistic situation.

黃永富，在允許延後付款情況下之確定性存貨模式的最佳補貨政策。未出版之博士論文，國立台灣科技大學工業管理系，台北市，民國九十一年。
廖友菁，在製造生產環境下之綠色供應鏈管理系統的建置與分析。碩士論文，明新科技大學工程管理研究所，新竹縣，民國九十三年。
黃惠民、楊伯中編著，供應鏈存貨系統設計與管理-觀念、策略與個案研究，滄海書局，民國九十六年。
陳文芳，考慮允許延後付款及倉庫容量有限情況下存貨模式之研究。國立台灣科技大學工業管理系，台北市，民國九十一年。
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