Chapter 16 - Plastic recycling: Challenges, opportunities, and future aspects

Abstract

Plastics, technically refined, light weight, and cheap, suit a broad range of applications. The problem with plastic not lies in its use, which is generally harmless, but in end-of-life management of products made from it. Plastics can be recycled by one of the three methods namely thermal recycling, chemical recycling, and mechanical recycling. The conventional methods of dumping plastics in landfills and incineration causes harm to the environment. The toxic chemicals may leach out in the landfills causing degradation of soil, and incineration causes emissions of carbon monoxide, carbon dioxide, nitrous oxide, nitrogen dioxide, sulfur dioxide, and other toxic gaseous products that are produced that cause global warming. Thus, it is high time that the circular economy approach need to be developed and plastics can be recycled or reprocessed to avoid problems in landfills and curb the emission of greenhouse gases. Therefore, the plastic waste generated is creating new challenges and opportunities to come up with best possible solution. This chapter explores chemical methods like low-temperature pyrolysis, catalytic degradation, and hydrothermal liquefaction for depolymerization. The methods encompass the use of ionic liquids and deep eutectic liquid mixture as green solvents and use of regenerative catalysts for the chemical treatment. The recycling methods provide a solution with complete recovery of the catalysts and solvents used, thus, generating no waste and following a complete circular economy. Every process is aimed at almost complete conversion of the polymer and obtaining the maximum yield of the product. The by-products generated also should be separated and many times these by-products also have a good economic value. This book chapter compiles the different research work done by the researchers in the field of recycling and progress in recovery management of different grades of plastics along with the various identification and separations techniques. In addition to this, this review focuses on the most recent advances in the chemical recycling of major polymers found in the plastic solid waste (PSW) and detailed studies of depolymerization of these polymers.