Advanced Recycling: An Umbrella of Recycling Technologies
Advanced recycling is a broad umbrella term – also called chemical recycling or molecular recycling – that refers to several different technologies that purify or break down plastic waste into its constituent building blocks, which can then be used to create new plastic products.
This burgeoning set of technologies is being deployed to convert used plastic into valuable materials. In complement with mechanical recycling, advanced recycling can help increase the types and amounts of plastic we can recycle.
Advanced recycling encompasses many different technologies that use solvents, heat, enzymes, and/or sound waves to purify or break down a wide range of used plastic to create polymers, monomers, oligomers, or hydrocarbon products that can then be reused instead of going to landfill.
Advanced recycling is a suite of different technologies.
Advanced recycling is a suite of different technologies. The most common – and those generally tending to be furthest along to scaling commercially – include:
Pyrolysis: Used plastics are heated in the absence of oxygen until thermally decomposed, then condensed and converted into valuable materials.
Gasification: Used plastics are heated in an oxygen-controlled atmosphere and converted into syngas that is then converted into valuable materials.
Depolymerization: Used plastics are broken into smaller molecules (such as monomers) that can be used to make multiple products. Includes solvolysis, methanolysis, and glycolysis technologies.
What is pyrolysis?
Pyrolysis technology is thought of as a potential game-changer in plastic recycling.
Pyrolysis is a thermal decomposition process that transforms materials by heating them in the absence of oxygen, preventing combustion. This method has been historically used to produce various materials, such as charcoal, roasted coffee, biofuels, and other chemical products. In plastic recycling, pyrolysis is employed to convert used plastics, which would otherwise be disposed of, into valuable products like pyrolysis oil, which can be used to make new plastics.
During the advanced recycling pyrolysis process, post-use plastics are heated to about 580-750 F (300-400 C), breaking them down into their molecular components. This differs from incineration, as there is no burning involved, and incineration takes place at much higher temperatures of 1,800 to 2,700 F (980 to 1,500 C) – 3 to 4 times hotter than pyrolysis facilities usually run. The pyrolysis process would fail if oxygen was present in the system, preventing the production of any sellable product, as Eric Hartz, president of Nexus Circular, told senators during Congressional testimony.
This manufacturing process thermally decomposes and then cools, condenses, and converts used plastics into valuable raw materials and products. In addition to the pyrolysis oil, the pyrolysis process also produces small amounts of non-condensable gases (about 10%-15%) that can be converted to heat or electricity to power the operating system, plus some char (about 4-5%).
The innovative application of pyrolysis for plastic recycling is relatively new and continues to evolve. By converting used plastics into reusable materials, pyrolysis has the potential to increase recycling rates and reduce reliance on virgin fossil resources.
What are the differences in the advanced recycling technologies?
This table from a City College of New York report shows examples of the inputs, outputs and final products of various advanced recycling technologies.
What is pyoil?
During pyrolysis, used plastic, which would otherwise be destined for disposal, is converted into pyrolysis oil, or “pyoil.” Pyoil is typically sent to petrochemical manufacturing facilities, where it is combined with hydrocarbons derived from fossil fuels. These mixed materials undergo processing to separate various fractions, which are then used to produce plastics, chemicals, waxes, lubricants, and other products.
Pyoil can be used in a manner similar to oil or natural gas. Each barrel of pyoil effectively replaces a barrel of virgin fossil-derived resources, contributing to a reduction in the demand for oil and natural gas extraction.
What is char? Is it the same as ash?
The pyrolysis process creates a small amount of char, approximately 4-5% of the process output, generated from cellulosic and other types of contamination, like labels or fillers. This char, or black carbon, has other applications such as asphalt production, or it can be landfilled according to local requirements.
Ash, which is a byproduct of burning or combustion, has a different chemical makeup than char. Char and ash are not the same.
Why would a company choose one technology over another?
Each technology under the advanced recycling umbrella has a unique set of traits. One of those traits, which is vitally important to the output it creates, is the type of plastic materials the technology can best process. So companies may choose a specific path based on feedstock potential. Below is a chart from a City College of New York report that outlines the potential application for various advanced recycling technologies. It is not intended to be a comprehensive list.
Investment company Closed Loop Partners says, “There are tradeoffs to each molecular recycling technology category and type. The viability of one solution depends on those metrics that matter most to a brand, investor, or community.” In an 18-month examination, it weighed the different technologies across a series of metrics to help investors understand the benefits and risks associated with advanced recycling technologies.