Page 83 - Plastics News July 2025
P. 83
IN THE NEWS
even these relatively homogeneous materials waste into an uncontaminated feedstock—such
up to the contamination specifications needed as the C5–C12 paraffins that would be an ideal
for food-contact use. In all, mechanical recycling naphtha feedstock for an ethylene cracker—
manages to capture only about 9% of plastics in poses considerable challenges. Plastics com-
the US, according to the US Environmental Pro- panies will need to overcome these challenges
tection Agency. if they are to debunk environmentalists’ objec-
tions and meet their own goals for reducing
Recyclers can tackle a few more resins with de- waste and carbon emissions.
polymerization processes that break down poly-
mers into their chemical precursors. For exam- The Pyrolysis Cauldron
ple, methanolysis can be used to recycle PET
products like fibers and sheets that aren’t ame- “We kind of joke sometimes that every day we
nable to mechanical methods. And firms have need to make a birthday cake, but the ingredi-
been breaking down nylon using hydrolysis for ents keep changing all the time, and the birthday
many years. cake better be good and taste the same,” says
Eric Hartz, cofounder and president of the py-
But the bulk of the plastics we use—the candy rolysis firm Nexus Circular. “There’s a kind of art
wrappers, stand-up pouches, potato chip bags, going on here when dealing with heterogeneous
protective packaging, single-use cups, frozen inputs as opposed to homogeneous. There’s
food bags, razors, toothpaste tubes, cotton not a perfect science to it about why some com-
swabs, and other objects of our daily lives—defy pounds behave the way they do in these envi-
both mechanical recycling and depolymeriza- ronments.”
tion.
This industry-backed path to plastics circular-
These items are constructed from multiple plas- ity chemically breaks down plastics into their
tics that are nearly impossible to separate. Plus component parts so they can be made into new
they are mostly made of polyolefins like poly- plastics.
ethylene and polypropylene, which have strong
carbon-carbon bonds that resist depolymeriza-
tion. For these mixed plastics, pyrolysis is the in-
dustry’s only currently viable tool for recovering
raw materials and making new polymers.
But a pyrolysis reactor isn’t a magic box that
can make the plastics industry’s waste problems 1. Pretreatment
vanish. The process is superficially simple: us-
ing high temperatures in the absence of oxygen The feedstock for pyrolysis plants is ideally
to break down plastics into a mixture of smaller made up of polyolefins such as polyethylene
molecules known as pyrolysis oil. Yet converting and polypropylene. Errant materials like oxygen-
the different kinds of plastics that can end up as containing polyethylene terephthalate and chlo-
rine-laden polyvinyl chloride are removed.
July 2025 PLASTICS NEWS 83
