Utilization Of Waste Plastics As Raw Materials In Biotechnology
Kalela, Anniliina (2026)
2026
Ympäristö- ja energiatekniikan DI-ohjelma - Programme in Environmental and Energy Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2026-07-27
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202607278499
https://urn.fi/URN:NBN:fi:tuni-202607278499
Tiivistelmä
Plastics are among the most important materials in modern society due to their low cost, durability, and versatility. Consequently, global plastic production has increased rapidly over recent decades and is expected to continue growing. However, these same properties also contribute to significant environmental challenges. Plastics degrade extremely slowly in the environment, persisting for centuries while gradually fragmenting into micro- and nanoplastics. As a result, the accumulation of plastic waste has become one of the most pressing environmental issues of our time.
Plastic waste is conventionally recycled through mechanical and chemical processes. However, these methods recover only a limited proportion of plastic waste and are constrained by several drawbacks, including degradation of material quality, high energy requirements, and limited suitability for mixed and contaminated waste streams, underscoring the need for new approaches. These limitations highlight the need for more sustainable recycling technologies. This thesis investigates the potential of biotechnological approaches for plastic waste recycling, compares them with conventional recycling methods, and evaluates their role in advancing a circular economy for plastics.
This thesis is based on a comprehensive literature review and four case studies focusing on enzymatic depolymerization and microbial conversion of plastic waste. Hydrolytic enzymes, including PET hydrolases and cutinases, depolymerize polyester plastics into their constituent monomers, which can subsequently be converted by genetically engineered microorganisms, particularly Pseudomonas putida, into value-added products. The case studies demonstrate the potential of biotechnological methods to recycle PET into virgin-equivalent materials, convert PET-derived monomers into polyhydroxyalkanoates and bio-based polyurethane, and valorize mixed plastic waste through integrated chemical-biological processes to produce valuable platform chemicals.
The findings suggest that biotechnological recycling can retain the carbon value of plastic waste while enabling its conversion into higher-value chemicals and materials. Although these technologies have not yet reached widespread industrial adoption, they represent a promising, sustainable alternative to conventional recycling methods and have significant potential to support the transition towards a circular plastics economy.
Plastic waste is conventionally recycled through mechanical and chemical processes. However, these methods recover only a limited proportion of plastic waste and are constrained by several drawbacks, including degradation of material quality, high energy requirements, and limited suitability for mixed and contaminated waste streams, underscoring the need for new approaches. These limitations highlight the need for more sustainable recycling technologies. This thesis investigates the potential of biotechnological approaches for plastic waste recycling, compares them with conventional recycling methods, and evaluates their role in advancing a circular economy for plastics.
This thesis is based on a comprehensive literature review and four case studies focusing on enzymatic depolymerization and microbial conversion of plastic waste. Hydrolytic enzymes, including PET hydrolases and cutinases, depolymerize polyester plastics into their constituent monomers, which can subsequently be converted by genetically engineered microorganisms, particularly Pseudomonas putida, into value-added products. The case studies demonstrate the potential of biotechnological methods to recycle PET into virgin-equivalent materials, convert PET-derived monomers into polyhydroxyalkanoates and bio-based polyurethane, and valorize mixed plastic waste through integrated chemical-biological processes to produce valuable platform chemicals.
The findings suggest that biotechnological recycling can retain the carbon value of plastic waste while enabling its conversion into higher-value chemicals and materials. Although these technologies have not yet reached widespread industrial adoption, they represent a promising, sustainable alternative to conventional recycling methods and have significant potential to support the transition towards a circular plastics economy.