3.01 Cycloplastic Economy

Preamble
This project relates to Task 3.2.2 “Treasure from waste: depolymerisation of plastics and synthetic textiles” of the Made in Italy Circolare e Sostenibile Extended Partnership project.
Key elements of the project
The fashion, textile, furniture and high-tech sectors produce huge quantities of synthetic waste polymers. These represent a significant environmental and economic issue, but also a valuable source of secondary raw materials. Valorisation of the latter into market products and materials requires the development of sustainable depolymerization methodologies via chemical recycling, which are currently in their early stage.
Expected outcomes
Development of sustainable technologies for the selective conversion of plastic residues obtained from the textile, footwear, upholstery and packaging industries (polyesters, polyamides, polyurethanes), as well as domestic post-consumer materials, into new plastic materials, pharmaceutical intermediates, solvents, cosmetic additives, synthetic textiles. Design of recyclable plastics and plastics from recycled materials.
Work Plan
The project will be broken down into the following activities, which represent the complementary possibilities and directions for plastic depolymerisation, depending on the strategy adopted, the design for recycling route selected and the plastic type to be processed. Each activity will have a leading Partner:

1. Advanced catalytic methods for sustainable molecular recycling of plastics (leader CNR)
   Innovative catalysts and processes will be developed, aiming to the cost effectiveness, low environmental impact and selectivity of depolymerisation. Heterogeneous catalysts and reaction sequences in cascade and in one-pot will be the preferred options. The use of ionic liquids and deep eutectic solvents will be considered, in combination with nonconventional methodologies (e.g. ultrasounds, microwaves).
2. Chemical recycling of thermosets and fiber reinforced composites (leader PoliMi)
   Novel solvolysis and microwave-assisted pyrolysis methods will be studied and developed for a cost-effective depolymerization in mild conditions of thermoset resins (polyesters, epoxies), and for an efficient glass and carbon fiber recovery from the corresponding composite materials. Physical features of recycled fibers will be evaluated through innovative micromechanical techniques. Organic fractions recovered by depolymerization will be evaluated for reuse in coating formulations. Materials circularity indicators for the proposed technologies will be calculated.
3. Chemical recycling of expanded polystyrene (EPS) (leader UniNa)
   Disposal of EPS is a main problem because of the high costs. Recycling of EPS will be explored according to a closed-loop model using the dissolution/polymerization method. The EPS waste will be dissolved in styrene, and the solution obtained will be subjected to a suspension polymerization, to give PS without polymer and solvent separation. This process has a strong potential to produce recycled EPS with good properties and will allow the recycling of EPS without the formation of secondary waste, according to the principles of circular economy. LCA tool will be used to evaluate sustainability.
4. Biological data mining for discovery and application of plastics depolymerisation enzymes (leader UniPd)
   The activity will include: 1) the exploration of (meta)genomic datasets and gene databases for the identification and analysis of enzymes useful for the depolymerization of plastics; 2) the study of
5. functional mechanisms related to enzymatic activity and gene regulation (including artificial intelligence, protein modelling, genomics and transcriptomics); 3) validation activities of the depolymerization potential of the identified enzymes using wet lab experiments; 4) existing metabolic pathways and enzyme selection based on the structure of depolymerization products, using predictive algorithms; 5) Codon-usage optimization, genetic engineering, cloning of the of the enzymatic candidates, and heterologous expression of enzymes using different hosts (e.g. E. coli and Synechocystis); 6) In vitro tests of the activity of the best enzymatic candidates obtained from heterologous expression.
6. Circular thermosetting materials from natural sources (leader PoliMi)
   This activity is aimed at preparing sustainable biobased thermoset polymers (TSP), mainly obtained from bio-sources derived from wastes. An eco-redesign will be made: TSP must undergo remoulding, recycling and depolymerisation, by triggering their degradation reactions. Polymers, such as polyesters from bio-based monomers and proteins, will be the TSP building blocks, avoiding low molecular mass chemicals. Circular bionanocomposites will be prepared, preferentially using biobased nanofillers.
7. Development of waste-based and biodegradable polymers with different monomeric composition (leader Sapienza)
   Production of microbial biopolymers (i.e. polyhydroxyalkanoates, PHA) with mixed microbial cultures (MMC) enriched into PHA-storing microorganisms. Either agro-industrial residues (e.g. wastewaters) upon conversion into organic acids or ad hoc formulated synthetic acid mixtures will be used as process feedstock. The effect of both acids composition and applied operating conditions on the PHA composition (namely hydrobutyrate, hydroxyvalerate and other monomers content) will be investigated and linked to the polymer properties which, in turn, affect its final application.