Chemical Engineering September 2022 - 46

Applied Technologies
Reshaping Plastic Waste with
Chemical Recycling
The following case study discusses a novel chemical recycling process for converting
plastic scrap into valuable material
S
the
ustainability has become
one of the main drivers for
innovation. Among the critical
sustainability issues is
recycling of end-of-use plastics.
The diversity of different types
of plastics presents problems for
mechanical
recycling processes,
but chemical recycling approaches
can offer a pathway to complement
mechanical recycling and help turn
plastic waste into a resource.
The plastic waste problem
Because plastics are versatile, durable,
lightweight and incredibly
adaptable, they are used in a wide
range of applications in product
packaging, housing,
automotive
and many others. The success of
plastics is partly a result of their low
cost, but also from their versatility to
meet highly demanding functional
requirements. Plastics production
has significantly increased over the
last few decades, both in terms of
amount, and also variety. Thousands
of different types of plastics
with highly specific product attributes
have been developed to fulfill
different demands.
With this boost in plastic production
and diversity, the challenge of
disposal has arisen, as plastic durability
renders it a serious problem for
the environment: end-of-life of plastics
contaminate waterways, appear
on shorelines and pollute areas on
land (Figures 1 and 2). An analysis
by the Ellen
MacArthur
Foundation
[1] states
that roughly
one-third of
the world's
plastic
packag -
ing waste
ends up in
the oceans
or in unmanaged
dumps
on
land. From collected plastics, more
than 50% is landfilled or incinerated,
meaning valuable resources are disposed
of in unsustainable ways.
Plastic as feedstock
The situation calls for a feedstock
change for future plastic production:
using recycled oils, biomass or even
CO2, rather than fossil petroleum.
Plastic waste has the potential to
be a resource, with dedicated procedures
for recycling that tackle the
global challenges of disposal and
benefit the circular economy. Public
pressure and government policies
can incentivize companies to explore
the development of more sustainable
recycling solutions with low
carbon emissions.
Mechanical recycling of plastics,
FIGURE 1. The volume and diversity of plastics
creates environmental problems for disposal
46
in which material is ground and regranulated,
is an option, but has
major limitations. Chief among them
lies in the fact that several types of
plastics (Table 1) simply do not mix.
So the scrap plastic needs to be
sorted to serve as input material for
new products Mechanical recycling
also mainly accepts monolayer plastics,
rather than multilayer, which
is one of the most common types
used in packaging. In addition, most
mechanically recycled plastics are
downcycled and cannot be used to
create food-grade packaging, with
FIGURE 2. The diagram shows how post-use plastics are currently used
the exception of PET (polyethylene
terephthalate) bottles.
Novel chemical recycling
For plastic waste that cannot be
mechanically recycled, such as
films and flexibles, chemical recycling,
in which polymer chains are
chemically cleaved, can overcome
some limitations of mechanical recycling
operations.
An example of this is from Plastic
Energy, a London-based company
that has focused on closed-loop
chemical recycling technologies.
Plastic Energy has developed a solution
that leverages this waste; the
company has developed a unique
and patented chemical-recycling
technology using a thermal anaerobic-conversion
(TAC) process to
treat plastics that cannot be mechanically
recycled.
" The TAC recycling process converts
plastic waste into a valuable
substance called TACOIL, which
serves as a feedstock to produce
new plastics, even suitable for foodgrade
packaging (Plastic2Plastic).
TACOIL can be used in petrochemical
crackers as a replacement for
fossil oils in the manufacturing of
virgin-quality plastics, which benefits
the circular economy, " explains Carlos
Monreal, CEO at Plastic Energy.
In Plastic Energy's process, plastics
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