Plastic waste is a major environmental challenge, but also a biotechnological opportunity as a unique carbon source. Modern biotechnology enables both recycling and upcycling of plastics. To achieve a plastics bioeconomy, intrinsic barriers must be overcome through enzyme, strain, and process engineering. This article discusses advances, challenges, and opportunities for various common plastics. Plastics are ubiquitous in daily life, with low cost and rapid production leading to overuse. Plastic production has increased over 100-fold since the 1950s, with estimates of tens of thousands of million metric tons by 2050. Only 14% is recycled, with the rest persisting in landfills or oceans, causing severe environmental consequences. Plastic waste can serve as a potent feedstock for bio-enabled recycling and upcycling. Mechanical and chemical degradation methods for plastics have drawbacks, including reliance on chromophores, high energy demands, and toxic byproducts. Biodegradation, which can occur at lower temperatures, offers a more efficient and specific method for breaking down plastics into individual components, enabling a true "biorefinery" approach. This allows for the specific breakdown of plastics into constituents that can be refactored into new products. Biodegradation is one component of a circular economy alongside chemical and mechanical recycling. Certain polymers, like PET, can be depolymerized back into original monomers, enabling an infinitely circular process. However, many plastics cannot be recycled multiple times due to degradation of polymer integrity. New technologies are needed to enhance recyclability for most plastics. Biodegradation faces intrinsic barriers such as high crystallinity, additives, and mixed plastic compositions. Preprocessing methods to lower crystallinity have been developed, but are not commercially scalable. Operating at temperatures above the glass transition temperature can reduce crystallinity impact but may inadvertently increase it. Recent efforts have used machine learning and protein engineering to improve enzyme thermostability, but this is limited to a small number of plastics. The selection between enzyme-based and whole-cell biodegradation depends on the application. Whole-cell biocatalysts are suitable for upcycling into value-added chemicals, while pure enzyme systems may be more advantageous for recircularization. Enzymatic degradation can produce specific product streams, enabling efficient recycling and upcycling. Common plastics like PET, polyolefins, polyurethanes, and others face unique challenges. PET can be fully depolymerized and repolymerized, while polyolefins are better suited for upcycling after biological degradation. Enzymatic degradation of polyurethanes requires a range of enzymes, and biodegradation of polyamides, polystyrene, and polyvinyl chloride is limited. Technoeconomic analysis and lifecycle assessment are crucial for evaluating the feasibility of biorecycling approaches. These analyses highlight the importance of feedstock pricing, pretreatment, and enzyme cost in determining the economic viabilityPlastic waste is a major environmental challenge, but also a biotechnological opportunity as a unique carbon source. Modern biotechnology enables both recycling and upcycling of plastics. To achieve a plastics bioeconomy, intrinsic barriers must be overcome through enzyme, strain, and process engineering. This article discusses advances, challenges, and opportunities for various common plastics. Plastics are ubiquitous in daily life, with low cost and rapid production leading to overuse. Plastic production has increased over 100-fold since the 1950s, with estimates of tens of thousands of million metric tons by 2050. Only 14% is recycled, with the rest persisting in landfills or oceans, causing severe environmental consequences. Plastic waste can serve as a potent feedstock for bio-enabled recycling and upcycling. Mechanical and chemical degradation methods for plastics have drawbacks, including reliance on chromophores, high energy demands, and toxic byproducts. Biodegradation, which can occur at lower temperatures, offers a more efficient and specific method for breaking down plastics into individual components, enabling a true "biorefinery" approach. This allows for the specific breakdown of plastics into constituents that can be refactored into new products. Biodegradation is one component of a circular economy alongside chemical and mechanical recycling. Certain polymers, like PET, can be depolymerized back into original monomers, enabling an infinitely circular process. However, many plastics cannot be recycled multiple times due to degradation of polymer integrity. New technologies are needed to enhance recyclability for most plastics. Biodegradation faces intrinsic barriers such as high crystallinity, additives, and mixed plastic compositions. Preprocessing methods to lower crystallinity have been developed, but are not commercially scalable. Operating at temperatures above the glass transition temperature can reduce crystallinity impact but may inadvertently increase it. Recent efforts have used machine learning and protein engineering to improve enzyme thermostability, but this is limited to a small number of plastics. The selection between enzyme-based and whole-cell biodegradation depends on the application. Whole-cell biocatalysts are suitable for upcycling into value-added chemicals, while pure enzyme systems may be more advantageous for recircularization. Enzymatic degradation can produce specific product streams, enabling efficient recycling and upcycling. Common plastics like PET, polyolefins, polyurethanes, and others face unique challenges. PET can be fully depolymerized and repolymerized, while polyolefins are better suited for upcycling after biological degradation. Enzymatic degradation of polyurethanes requires a range of enzymes, and biodegradation of polyamides, polystyrene, and polyvinyl chloride is limited. Technoeconomic analysis and lifecycle assessment are crucial for evaluating the feasibility of biorecycling approaches. These analyses highlight the importance of feedstock pricing, pretreatment, and enzyme cost in determining the economic viability