This lecture explores the sustainable design and processing of aliphatic polyesters, focusing on function-driven design, chemical recycling, and the properties range expansion through microstructure design. It covers topics such as fermentation, photosynthesis, degradation mechanisms, and thiol-functionalized polyesters. The lecture also delves into the degradation profile of a library of polyesters, the factors affecting the degradation rate, and the environmental impact considerations. Additionally, it discusses the challenges of environmentally sustainable packaging, the role of polyesters in addressing these challenges, and the outlook for sustainable polymers obtained from renewable resources.