Emerging Biochemical Conversion for Plastic Waste Management: A Review

Abstract

In recent years, vast amounts of plastic waste have been released into the environment worldwide, posing a severe threat to human health and ecosystems. Despite the partial success of traditional plastic waste management technologies, their limitations underscore the need for innovative approaches. This review provides a comprehensive overview of recent advancements in chemical and biological technologies for converting and utilizing plastic waste. Key topics include the technical parameters, characteristics, processes, and reaction mechanisms underlying these emerging technologies. Additionally, the review highlights the importance of conducting economic analyses and life cycle assessments of these emerging technologies, offering valuable insights and establishing a robust foundation for future research. By leveraging the literature from the last five years, this review explores innovative chemical approaches, such as hydrolysis, hydrogenolysis, alcoholysis, ammonolysis, pyrolysis, and photolysis, which break down high-molecular-weight macromolecules into oligomers or small molecules by cracking or depolymerizing specific chemical groups within plastic molecules. It also examines innovative biological methods, including microbial enzymatic degradation, which employs microorganisms or enzymes to convert high-molecular-weight macromolecules into oligomers or small molecules through degradation and assimilation mechanisms. The review concludes by discussing future research directions focused on addressing the technological, economic, and scalability challenges of emerging plastic waste management technologies, with a strong commitment to promoting sustainable solutions and achieving lasting environmental impact.

Keywords: catalyst; circular economy; conversion; mechanism; plastic waste.

Figure 1

The mechanism of chemical conversion of plastic waste.

Figure 2

The catalytic mechanism of acidic and alkaline catalysts in the pyrolysis process.

Figure 3

The catalytic mechanism of bifunctional catalysts in the pyrolysis process.

Figure 4

The mechanism of biodegradation of plastic waste.

Figure 5

The mechanism of improving the performance of plastic-degrading enzymes. (A) Enhancing the thermal stability of enzymes; (B) enhancing the attachment of plastic waste to the active sites of enzymes; (C) enhancing the interaction between plastic waste and the surface of enzymes; (D) refining additional functions of enzymes (modified from [78]).

Figure 6

Comparison of the environmental potential of chemical recycling and other recycling methods. (A) Energy recovery in municipal solid waste incinerators; (B) energy recovery in cement kilns; (C) mechanical recycling (Modified from [129]). Red represents negative environmental potential. Green represents positive environmental potential. White represents values equal to zero. Gray represents that chemical recycling has been omitted.