Demand for recycled polyethylene terephthalate (PET), or recycled polyester, has increased significantly in recent years. There are many advantages to recycled polyester, including reduced energy consumption in the manufacturing process as compared to producing virgin polyester; reduced CO2 emissions, and reduced extraction of crude oil and natural gas to make virgin plastic. There are two techniques for producing recycled polyester: mechanical recycling and chemical recycling also known as advanced recycling.

Bales of crushed plastic ready to recycled by either mechanical recycled or advanced recycled methods — As the technology improves, recycled polyester and plastics stand to eventually replace virgin materials in manufacturing.

Mechanical versus Chemical Recycling

Mechanical recycling involves shredding recycled PET bottles and pressing the flakes into consistently shaped pellets that are melted and extruded into recycled polyester fiber. Mechanical recycling requires no chemicals, save for detergents to clean the original recycled material, but the process can weaken the fiber which then must be mixed with virgin fiber to result in acceptable strength. To date, mechanical recycling is the most affordable and widely used process to produce recycled polyester.

Shredding recycled PET bottles is an initial steps in the mechanical recycling process recycling plastic.

Chemical recycling uses a chemical process to break down PET products into their molecular parts so that they can be reformed into a yarn of equal strength. Unlike mechanical recycling, the quality of the chemically recycled polyester remains consistent and does not degrade its performance. However, chemical recycling is currently more expensive than the alternative and must be scaled up to achieve more widespread adoption.

Advanced Recycling Technologies

In addition to chemical recycling, or depolymerization, industry experts are constantly investigating new and innovative methods for recycling plastics. The industry refers to these technologies as “Advanced Recycling Technologies,” a term established by the American Chemistry Council (ACC). According to the ACC, the term advanced recycling accomplishes two things: it identifies technologies that go deeper into the polymer than the mechanical recycling process and it also confirms that these processes are, indeed, a form of recycling, even though they differ from traditional recycling. There are three main methods of advanced recycling:

Purification, which use a solvent or chemical to precipitate the polymer out of a solution, leaving behind colorants, additives, and other contaminants. Some of the most common types of purification include solvent extraction and chromatography. Pros: Purification results in a clean and clear polymer and removes contaminants, colorants, and additives. This results in a recycled product that has many of the characteristics of virgin polymers. Cons: Purification does not restore the polymer to its virgin molecular level, which means that it retains the heat history of melting and remelting and can alter the molecular weight and viscosity of the plastic. Purification is also more energy intensive than mechanical recycling, but less than chemical recycling.

Depolymerization, which breaks the chemical bonds in the complex chains that make up polymers. In this process, additives and colorants are separated from chemicals and monomers, the latter of which can be put back into reactors to make a recycled polymer identical to its virgin counterpart. Pros: The recycled polymer is identical to its virgin counterpart. Cons: The technology is not currently operating at scale, and when it does, there will be a need for massive quantities of materials to be recycled than are currently available. Also, the technology currently has a higher environmental footprint than mechanical recycling.

Conversion reprocesses plastic products into other sellable, tradable commodities. Pros: Once proven and scaled, conversion technology could prevent massive amounts of plastics from ending up in landfills or the world’s oceans. Cons: Not every repurposed product can be considered recycled. To meet the standard of being recycled, the new product must be reprocessed into materials instead of fuels or energy.

Discarded plastic washed up on a beach. — Recycling plastic through mechanical or chemical processes can keep polymers out of our natural environment

Even though these technologies are still emerging and innovating, recycling plastic is preferable to using virgin components. The most common way to recycle plastic is through mechanical recycling, but that process degrades the product’s quality over time. Chemical recycling preserves the quality of the original material but is expensive and has a larger environmental footprint. Nevertheless, manufacturers are demanding more recycled materials, which is driving innovation and allowing producers to scale up current technologies. Eventually, recycling plastics will allow us to keep polymers out of trash streams and will allow us to continue to produce necessary and valuable products without using virgin materials.

To share your thoughts on recycled polyester or to learn more about SAYA fiber, please contact us at change@sayarenew.com

Chemical Recycling of plastics in a laboratory — Chemical Recycling of plastics

Chemical Recycling of Plastics: Advanced Recycling Technology

Chemical recycling of plastics, also called advanced recycling, is taking plastic waste and reducing it back to its original molecular form, which is raw petroleum. This PET can then go back into manufacturing system and eventually be processed into entirely new polyester fiber or plastic items.

Although chemical recycling is more expensive than mechanical recycling of plastic, the raw petroleum is not degraded and could be used and recycled again and again feeding an “infinite” recycling system.

Chemical Recycling Process

Chemical recycling is accomplished by dissolving the plastic with enzymes or chemicals or using heat to break down plastics into their original components.

Chemical recycling is used with plastics which are difficult to sort and process mechanically. It is also used to recycle plastics in food contact applications and packaging. The processes used in advanced recycling of used plastics either using chemicals or thermal processes takes place in the absence of oxygen so emissions from advanced recycling are generally considered very low.

New Technologies in Chemical Recycling

Currently, there are a number of ongoing projects in the plastics and recycling industries to make advanced recycling more widespread. Two processes which are being refined for wider use are Pyrolysis and Gasification.

Pyrolysis, turns plastics which are recovered from solid waste (garbage) into a synthetic crude oil that can be refined into diesel fuel, gasoline, heating oil or waxes. Using pyrolysis to convert plastics into fuel reduces greenhouse gas emissions by 14% and water consumption by 58%, and it saves up to 96% in traditional energy use as opposed to refining conventional crude oil.

Gasification turns materials recovered from solid waste (garbage) into a synthesis gas, or “syngas,” which can be used for electric power generation or converted into fuel or ethanol and methanol. It can also also be used to make new plastics that go into consumer products.

To share your thoughts on recycled plastic or to learn more about SAYA fiber, please contact us at change@sayarenew.com