In addition to pursuing profits, more and more international enterprises are beginning to pay attention to environmental sustainability and corporate social responsibility (CSR). How to effectively encourage enterprises to undertake more CSR and maintain the sustainable development of society has become an urgent task for managers and researchers. Under this background, this paper considers the recycling of used products for environmental sustainability and takes into account profit donation as a CSR investment. Aiming at the decision-making of single-cycle closed-loop supply chain (CLSC) with a dominant retailer when considering government subsidies and CSR investment, and based on the Stackelberg Game analysis technology, we formulate three distinct donation (CSR investment) models; the centralized system’s donation model, the manufacturer’s donation model, and the retailer’s donation model, and by doing system comparisons and numerical examples to analyze the impact of government subsidy and CSR investment on new product pricing and waste product recovery from the perspectives of government, environment and CLSC system. The results show that government subsidy is not only conducive to expanding market demand and increasing waste recycling rates, but also to improving CSR investment levels. Under the two decentralized decision-making models, regardless of whether the dominant retailer makes CSR investment, she can always get more channel profits than the manufacturer. From the view of environmental, economic, and social perspectives, the manufacturer makes CSR investment a better choice, and at this time the government has the best effect of implementing subsidy. Finally, based on the principle of cost sharing, a CSR cost sharing contract which can realize the coordination of CLSC is designed to solve the channel conflict and optimize the decision-making. Counterintuitively, the dominant retailer can gain more profits when it bears more cost in the CSR cost sharing contract.

Manufacturing enterprises often face the problem of an increasing production cost per unit of output-that is, diseconomies of scale-due to technology or management ability. This paper examines the collection channel selection and coordination strategies of a dual-channel closed-loop supply chain (CLSC) in the presence of manufacturer diseconomies of scale. Decision models for a dual-channel CLSC with single-and dual-channel waste product collection are constructed from the perspectives of centralized and decentralized decision-making, and the effects of diseconomies of scale and sales/collection competition on the pricing of new products and the waste product collection rate are analyzed. Moreover, criteria for selecting a collection channel are given for CLSC members and the system as a whole, and two-part tariff contracts are designed to coordinate the dual-channel CLSC under different collection channels. We find that the optimal pricing decision and members' profits are negatively correlated with diseconomies of scale and positively correlated with sales competition. Under the dual-channel sales structure, the direct sales volume is more than twice that of retail sales, and the stronger the sales competition, the more pronounced this advantage is. Further, from the perspective of collection, when collection competition is weak, the dualchannel collection strategy is optimal, while as competition increases, the single-channel collection strategy may be better. The manufacturer's collection rate is more than twice that of the retailer under dual-channel collection, and the stronger collection competition is, the larger this gap is. Finally, the conclusions are verified by numerical simulation, and management insights are proposed. INDEX TERMSDiseconomies of scale; Dual-channel closed-loop supply chain; Pricing decision; Collection strategy; Coordination