Unilever pioneers solution that enables recycling of black plastic
Image credit: The Drum
Unilever UK has pioneered the use of a new, detectable black pigment for its
High Density Polyethelyne (HDPE) bottles for its TRESemmé and Lynx
brands, so they can be detected by recycling plant scanners and sorted for
recycling. This means that roughly 2,500 more tonnes of plastic bottles can now
potentially be sorted and sent for recycling each year — equivalent to the
weight of 200 London buses, or 1,250 family-sized cars.
To date, standard black plastic — commonly used as trays for microwaveable,
prepared meals; as well as bottles and other containers — goes undetected by the
automatic, optical sorting machines in recycling plants because they use near
infra-red light, which is absorbed by the ‘carbon black’ pigment traditionally
used to color them. This effectively makes them invisible to the sorter and
leads to them being rejected and sent for waste.
Through extensive trials — in partnership with RECOUP and waste management
partners Veolia, SUEZ, Viridor and TOMRA — Unilever has proven
that this new pigment can be technically detected within their material
recycling facilities in the UK. The company says it will share the knowledge and
expertise from developing this technical solution for detectable black bottles
with others in the industry, as well as to other markets globally, to enable
wide use of this technology and approach.
“We have deployed an innovative solution within the software and invested in our
sorting technology at our flagship recycling facility in Southwark, and this —
together with Unilever modifying the pigment in the black dye for their HDPE
packaging — enables it to be successfully detected. If all recyclers and
manufacturers follow this, black plastic becomes detectable black,” explains
Richard Kirkman, Chief Technology and Innovation Officer at Veolia UK &
Ireland. “Adjusting the detection mechanism in this way — with both technology
and packaging modified — was the key. It’s the first time a hi-tech solution
like this has been applied to black plastics and can be rolled out at scale — a
eureka moment for recycling and a rallying call for similar partnerships to take
shape. This is exactly the kind of thing the [UK] Plastics
Pact
was set up for, and it’s inspiring a generation of engineers.
“Recycling is a chain of events from manufacturer, consumer to recycler and we
need each part of the chain to make changes to have successful, scalable
results."
Unilever’s solution will enable TRESemmé and Lynx bottles to be detected by
recycling scanners, with minor adjustments at the material recycling facilities,
so they can be technically separated, sorted and sent for recycling, becoming a
useful resource rather than ending up as waste.
The new detectable bottles will be phased in this year and will allow Unilever
to further ‘close the loop’ and include the recycled black plastic in new
packaging. In 2019, TRESemmé and Lynx will both introduce a minimum of 30
percent recycled material into their packs — one step closer to Unilever’s goal
of ensuring all of its plastic packaging is reusable, recyclable or compostable
by 2025, as well as increasing use of recycled plastic content in its packaging.
This move to using the new detectable black plastic is part of Unilever UK’s
commitment to the UK Plastics Pact and its new #GetPlasticWise campaign, a
Five-Point Plastic Plan that aims to tackle plastic waste in the UK; and move
towards a closed loop — where plastic stays within the plastic economy, not the
environment.
“Tackling plastic waste is complex and involves collaboration across the supply
chain,” said Helen Bird, Strategic Engagement Manager at
WRAP, which manages The UK Plastics Pact. “We welcome this move
by Unilever and steps taken by waste management companies to trial the sorting
of the packaging. We now call for wide scale adoption of detectable black
pigments by brands and retailers, and the sorting and reprocessing of that
packaging by the recycling sector.”
In addition to helping to achieve its 2025 goals around packaging, Unilever’s
Five-Point Plan sees the company collaborating with partners on solutions, while
supporting and educating consumers on how they can reduce plastic consumption.
Sebastian Munden, General Manager of Unilever UKI, said: “We’ve been working
on a solution for black plastic for some time, and this move to using detectable
black plastic in our TRESemmé and Lynx bottles means we will potentially be
removing around 2,500 tonnes of plastic from the waste stream. We’re proud our
innovation will help us towards achieving our [2025 goal], as well as making a
significant contribution towards the UK Plastics Pact targets. We’d like to
thank our industry partners for their part in working with us to make this
possible.”
Berkeley Lab breakthrough recycles plastic from the inside out
Image credit: Berkeley Lab
Meanwhile, even the most recyclable plastic,
PET,
is only recycled at a rate of 20-30
percent,
with the rest typically going to incinerators or landfills, where the
carbon-rich material takes centuries to decompose.
But a team of researchers at the US Department of Energy’s (DOE)
Lawrence Berkeley National Laboratory (Berkeley Lab) has just designed a
recyclable plastic that, like a Lego playset, can be disassembled into its
constituent parts at the molecular level, and then reassembled into different
shapes, textures and colors, again and again, without loss of performance or
quality. The new material, called poly(diketoenamine), or PDK, was
discussed in the journal Nature
Chemistry.
“Most plastics were never made to be recycled,”
said
lead author Peter Christensen, a postdoctoral researcher at Berkeley
Lab’s Molecular Foundry. “But we have discovered a
new way to assemble plastics that takes recycling into consideration from a
molecular perspective.”
Christensen was part of a multidisciplinary team led by Brett
Helms, a staff scientist at the Molecular Foundry; along with Angelique Scheuermann (then of UC Berkeley) and Kathryn Loeffler
(then of the University of Texas at Austin), who were undergraduate
researchers at the time of the study.
All plastics, from water bottles to automobile parts, are made up of large
molecules called polymers, which are composed of repeating units of shorter
carbon-containing compounds called monomers According to the researchers, the
problem with many plastics is that additives — such as fillers that make a
plastic tough, or plasticizers that make a plastic flexible — are tightly bound
to the monomers and stay in the plastic even after it’s been processed at a
recycling plant.
During processing at such plants, plastics with different chemical compositions
— such as hard, stretchy, clear or candy-colored plastics — are mixed together
and ground into bits. When that hodgepodge of plastic bits is melted to make a
new material, it’s hard to predict which properties it will inherit from the
original plastics.
This unpredictability has prevented plastic from becoming what many consider the
Holy Grail of recycling: a “circular” material, whose original monomers can be
recovered for reuse for as long as possible, or “upcycled” to make a new,
higher-quality product.
So, for example — when a reusable shopping bag made from recycled plastic gets
threadbare with wear and tear, it can’t be upcycled or even recycled to make a
new product. And once the bag has reached its end of life, it’s either
incinerated to make heat, electricity or fuel, or ends up in a landfill, Helms
said.
“Circular
plastics
and plastics upcycling are grand challenges,” he said. “We’ve already seen the
impact of plastic waste leaking into our aquatic ecosystems, and this trend is
likely to be exacerbated by the increasing amounts of plastics being
manufactured and the downstream pressure it places on our municipal recycling
infrastructure.”
Recycling plastic one monomer at a time
The researchers want to divert plastics from landfills and the oceans by
incentivizing the recovery and reuse of plastics, which could be possible with
polymers formed from PDKs.
“With PDKs, the immutable bonds of conventional plastics are replaced with
reversible bonds that allow the plastic to be recycled more effectively,” Helms
said.
Unlike conventional plastics, the monomers of PDK plastic could be recovered and
freed from any compounded additives simply by dunking the material in a highly
acidic solution. The acid helps to break the bonds between the monomers and
separate them from any chemical additives.
“We’re interested in the chemistry that redirects plastic lifecycles from linear
to circular,” Helms said. “We see an opportunity to make a difference for where
there are no recycling options.” That includes adhesives, phone cases, watch
bands, shoes, computer cables, and hard thermosets that are created by molding
hot plastic material.
The researchers first discovered the exciting circular property of PDK-based
plastics when Christensen was applying various acids to glassware used to make
PDK adhesives, and noticed that the adhesive’s composition had changed. Curious
as to how the adhesive might have been transformed, Christensen analyzed the
sample’s molecular structure with an NMR (nuclear magnetic resonance)
spectroscopy instrument. “To our surprise, they were the original monomers,”
Helms said.
After testing various formulations at the Molecular Foundry, they demonstrated
that not only does acid break down PDK polymers into monomers, but the process
also allows the monomers to be separated from entwined additives. Next, they proved that the recovered PDK monomers can be remade into polymers,
and those recycled polymers can form new plastic materials without inheriting
the color or other features of the original material — so if that broken black
watchband is made with PDK plastic, it could find new life as a computer
keyboard; or it could be upcycled by adding additional features, such as
flexibility.
Moving toward a circular plastic future
The researchers believe that their new recyclable plastic could be a good
alternative to many nonrecyclable plastics in use today.
“We’re at a critical point, where we need to think about the infrastructure
needed to modernize recycling facilities for future waste sorting and
processing,” Helms said. “If these facilities were designed to recycle or
upcycle PDK and related plastics, then we would be able to more effectively
divert plastic from landfills and the oceans. This is an exciting time to start
thinking about how to design both materials and recycling facilities to enable
circular plastics."
The researchers say they plan to develop PDK plastics with a wide range of thermal
and mechanical properties for applications as diverse as textiles, 3D printing
and foams. In addition, they are looking to expand the formulations by
incorporating plant-based materials and other sustainable sources.
The Molecular Foundry is a DOE Office of Science User Facility that specializes
in nanoscale science. This work was supported by the DOE’s Laboratory Directed
Research and Development (LDRD) program.
Get the latest insights, trends, and innovations to help position yourself at the forefront of sustainable business leadership—delivered straight to your inbox.
Sustainable Brands Staff
Published May 23, 2019 8am EDT / 5am PDT / 1pm BST / 2pm CEST