Page 49 - Plastics News June 2024

FEATURE NEWS

searchers at Worcester Polytechnic materials in the absence of air until value contained in the chemical bonds
Institute and the University of Bath the bonds of a molecule break apart. of polystyrene, meaning that the pro-
reveals a breakthrough using a new Polystyrene conveniently breaks pri- cess is energy efficient.
approach. They report that it’s now marily into a monomer. This opens the As well, multiple pathways exist for
conceivable that up to 60% of the poly- window for using pyrolysis to recover styrene production at costs that are
styrene used today could be replaced monomer followed by repolymeriza- competitive with global historical aver-
by recycled polystyrene, rPS. tion to produce “good as new” poly- ages over the past several years. That
styrene.
As a sustainable bonus, increased means that “good as new” post-con-
recycling of PS can reduce the need However, there’s a catch: monomer sumer polystyrene is not just an idea
for new polystyrene production, and purity after pyrolysis is insufficient for in the lab.
thereby contribute to the decarboniza- repolymerization. To complete their analysis, the team
tion of plastics. The holdup was short lived when the considered greenhouse gas emissions.

The approach involves breaking down Bath-WPI team analyzed a multi-step Technologies such as pyrolysis and
and re-creating polystyrene. In a paper process to convert polystyrene into its distillation have faced criticism in re-
in the Chemical Engineering Journal, monomer and then use distillation to cent years because of their association
researchers analyzed a simple process purify the monomer. with greenhouse gas emissions. How-
combining pyrolysis and distillation This two-step process consists en- ever, the research team found that the
that has the potential to be scalable, tirely of scalable technologies that are new process can reduce greenhouse
cost-competitive, and energy-efficient. among the most reliable processes gas emissions relative to polymer
The team outlines its findings in a paper used in chemical processing. Because combustion at an investment cost of
titled” Thermodynamic and economic it relies on proven technologies, this about $1.5/ton of carbon dioxide. This
analysis of a deployable and scalable means that the entire process should is comparable in costs associated with
process to recover Monomer-Grade be readily deployable soon. “low-hanging fruit” such as installing
styrene from waste polystyrene”, PS recycling clears energy and eco- energy efficient light bulbs.
which was published in the Chemical nomic barriers. The researchers concluded that not
Engineering Journal. only does the new combination pro-
The challenges are centered energy cess consist of scalable, proven
DANIELVFUNG ISTOCK VIA GETTY use and economics, which is where technologies, it’s realistic in terms of
IMAGES PLUS the team focused its efforts. Interest- economics and energy use, and a net

savings of emissions relative to com-
bustion. These are all positives that
will help keep polystyrene out of water,
food and, ultimately, out of people.

Continued work is focused on improv-
ing the polystyrene process by includ-
ing additional steps for obtaining more
products, scenarios for mixed plastic
waste streams, and developing new,
and even more efficient technologies
for plastic recycling.
Source – Plastics Today

The core technology that the team ingly, the energy requirements for the
analyzed is pyrolysis, which heating entire process are much less than the

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