(612g) Evaluating the Economic and Environmental Performance of Methanolysis Processes for Polyester Textile Valorization

The textile industry is one of the largest industrial sectors in the world, with an approximate global market value of 1 trillion USD. The major challenge with this sector is its detrimental environmental burden over its production, use phase, and disposal [1,2]. The current rise in fast fashion and the predominant linear economy in the textile industry have also contributed to these issues [3,4]. Recent reports indicate that the textile industry represents around 5% of the total global waste, producing between 65 and 92 million tons of textile waste annually. It also contributes to 10% of global carbon emissions and 20% of the world’s wastewater, with projections suggesting a continued increase in these figures [5-7]. In the United States, over three-quarters of the textile waste generated is landfilled or incinerated, whilst less than 1% is recycled back to textile materials [8].

Textile recycling technologies can help ensure a continuous supply of raw materials, facilitate pollution reduction, and promote energy efficiency and resource conservation [9,10]. Textile recycling is generally classified into mechanical and chemical recycling. Mechanical recycling is the predominant form of textile recycling used for shredding and carding waste textiles to extract fibers that can subsequently be spun into yarns [11]. However, issues such as the inability to handle mixed textile waste and material quality reduction limit the potential of this method as a standalone recycling technology [12]. Chemical recycling, on the other hand, is used to disintegrate synthetic textiles (derived from petroleum) into their monomeric units, which can then be polymerized to form materials of virgin-grade quality (closed-loop recycling) or used in the production of other materials (open-loop recycling) [13].

The most common chemical recycling methods for polyester textile waste are methanolysis, glycolysis, and hydrolysis. Monomers such as terephthalic acid (TPA) and dimethyl terephthalate (DMT) are direct products of some of these chemical depolymerization reactions. These monomers can be used to produce dyes and pigments, insect repellents, polyurethane foams, and polyester coating resins, among other applications [14,15], or they can be reused for textile manufacturing. This presents a potential avenue for exploring the open and closed-loop recycling of textile materials. Recent studies have shown that this recycling method (obtaining monomers) can be less energy-intensive than the virgin production of monomers [16]. Hydrolysis is the least favored method of chemical recycling, as it produces acid salts, resulting in a very energy- and capital-intensive process [17,18]. Glycolysis is the most widely applied chemical recycling method, although recent studies have shown that methanolysis has a competitive advantage. Compared to glycolysis, methanolysis produces high-quality resins, can handle low-purity feed, is more economically feasible, and shows good potential for both textile and plastic recycling [17-20]. Despite this potential, the economic and environmental performance of the methanolysis process for producing DMT and ethylene glycol (EG) remains underexplored.

Four variants of the methanolysis process for textile depolymerization have been reported: low-temperature, subcritical, supercritical, and vapor-phase methanolysis [21]. A long residence time and unfavorable reaction conditions result in low-temperature and supercritical methanolysis being less desired [22]. Therefore, in this work, we model and quantify the economic and environmental benefits of producing DMT and EG through the subcritical and vapor-phase process variants of the methanolysis process and then compare our results with those from the production of these solvents and monomers from virgin or fossil sources. We propose a computational framework integrating process modeling, techno-economic analysis (TEA), and life cycle assessment (LCA) to provide valuable insights into a sustainable approach to closing the textile loop.

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