Plastics play a crucial role in modern life, but their accumulation poses a serious threat to both the environment and human health. Due to their effects on the terrestrial and aquatic environment, it is essential to develop sustainable approaches to dispose of waste plastics. Traditional methods of plastic disposal, such as burning and landfilling, are problematic since they produce hazardous byproducts. Biodegradation is a potentially effective, eco-friendly approach which uses microbial consortia or isolated enzymes to break down plastic waste. Enzymes interact with plastic surfaces and hydrolyse the large polymer chains into smaller units. These byproducts can then be utilised as carbon sources by microbes, which are eventually converted into CO₂ and water. This review explores the principal approaches to plastic degradation, with a focus on existing and emerging polymers made to be readily biodegradable. In addition, sustainable valorisation methods for converting plastic waste into valuable byproducts are considered. The implementation of a circular plastic economy is expected to lead to further development, including scaling up of efficient plastic bio-upcycling processes, which can serve to stimulate environmental waste removal and value-added use of post-consumer plastic streams.