A new environmental and technological analysis suggests that a revolutionary eco-friendly plastic is almost ready to hit the shelves
From: Lawrence Berkeley National
Laboratory
April 22, 2021 -- Plastics are
a part of nearly every product we use on a daily basis. The average person
in the U.S. generates about 100 kg of plastic waste per year, most of which
goes straight to a landfill. A team led by Corinne Scown, Brett Helms, Jay Keasling,
and Kristin Persson at Lawrence Berkeley National Laboratory (Berkeley Lab) set
out to change that.
Less than two years ago, Helms announced the invention of a new plastic that could
tackle the waste crisis head on. Called poly(diketoenamine), or PDK, the
material has all the convenient properties of traditional plastics while
avoiding the environmental pitfalls, because unlike traditional plastics, PDKs
can be recycled indefinitely with no loss in quality.
Now, the team
has released a study that shows what can be accomplished if
manufacturers began using PDKs on a large scale. The bottom line? PDK-based
plastic could quickly become commercially competitive with conventional
plastics, and the products will get less expensive and more sustainable as time
goes on.
“Plastics were never designed to be
recycled. The need to do so was recognized long afterward,” explained Nemi
Vora, first author on the report and a former postdoctoral fellow who worked
with senior author Corinne Scown. “But driving sustainability is the heart of
this project. PDKs were designed to be recycled from the get-go, and since the
beginning, the team has been working to refine the production and recycling
processes for PDK so that the material could be inexpensive and easy enough to
be deployed at commercial scales in anything from packaging to cars.”
The study presents a simulation for a
20,000-metric-ton-per-year facility that puts out new PDKs and takes in used
PDK waste for recycling. The authors calculated the chemical inputs and
technology needed, as well as the costs and greenhouse gas emissions, then
compared their findings to the equivalent figures for production of
conventional plastics.
“These days, there is a huge push for
adopting circular economy practices in the industry. Everyone is trying to
recycle whatever they’re putting out in the market,” said Vora. “We started
talking to industry about deploying 100% infinitely recycled plastics and have
received a lot of interest.”
“The questions are how much it will
cost, what the impact on energy use and emissions will be, and how to get there
from where we are today,” added Helms, a staff scientist at Berkeley Lab’s Molecular Foundry. “The next phase of
our collaboration is to answer these questions.”
Checking the boxes of cheap and easy
To date, more than 8.3 billion metric
tons of plastic material have been produced, and the vast majority of this has
ended up in landfills or waste incineration plants. A small proportion of
plastics are sent to be recycled “mechanically,” meaning they are melted down
and then re-shaped into new products. However, this technique has limited
benefit. Plastic resin itself is made of many identical molecules (called
monomers) bound together into long chains (called polymers). Yet to give
plastic its many textures, colors, and capabilities, additives like pigments,
heat stabilizers, and flame retardants are added to the resin. When
many plastics are melted down together, the polymers become mixed with a slew
of potentially incompatible additives, resulting in a new material with much
lower quality than newly produced virgin resin from raw materials. As such,
less than 10% of plastic is mechanically recycled more than once, and recycled
plastic usually also contains virgin resin to make up for the dip in quality.
PDK plastics sidestep this problem
entirely – the resin polymers are engineered to easily break down into
individual monomers when mixed with an acid. The monomers can then be separated
from any additives and gathered to make new plastics without any loss of
quality. The team’s earlier research shows that this “chemical recycling”
process is light on energy and carbon dioxide emissions, and it can be repeated
indefinitely, creating a completely circular material lifecycle where there is
currently a one-way ticket to waste.
Yet despite these incredible properties,
to truly beat plastics at their own game, PDKs also need to be convenient.
Recycling traditional petroleum-based plastic might be hard, but making new
plastic is very easy.
“We’re talking about materials that are
basically not recycled,” said Scown. “So, in terms of appealing to
manufacturers, PDKs aren’t competing with recycled plastic – they have to
compete with virgin resin. And we were really pleased to see how cheap and how
efficient it will be to recycle the material.”
Scown, who is a staff scientist in
Berkeley Lab’s Energy Technologies and Biosciences Areas, specializes in
modeling future environmental and financial impacts of emerging technologies.
Scown and her team have been working on the PDK project since the outset,
helping Helms’ group of chemists and fabrication scientists to choose the raw
materials, solvents, equipment, and techniques that will lead to the most
affordable and eco-friendly product.
“We’re taking early stage technology and
designing what it would look like at commercial-scale operations” using
different inputs and technology, she said. This unique, collaborative modeling
process allows Berkeley Lab scientists to identify potential scale-up
challenges and make process improvements without costly cycles of trial and
error.
The team’s report, published in Science
Advances, models a commercial-scale PDK production and recycling pipeline based
on the plastic’s current state of development. “And the main takeaways were
that, once you’ve produced the PDK initially and you’ve got it in the system,
the cost and the greenhouse gas emissions associated with continuing to recycle
it back to monomers and make new products could be lower than, or at least on
par with, many conventional polymers,” said Scown.
Planning to launch
Thanks to optimization from process
modeling, recycled PDKs are already drawing interest from companies needing to
source plastic. Always looking to the future, Helms and his colleagues have
been conducting market research and meeting with people from industry since the
project’s early days. Their legwork shows that the best initial application for
PDKs are markets where the manufacturer will receive their product back at the
end of its lifespan, such as the automobile industry (through trade-ins and
take-backs) and consumer electronics (through e-waste programs). These companies
will then be able to reap the benefits of 100% recyclable PDKs in their
product: sustainable branding and long-term savings.
“With PDKs, now people in industry have
a choice,” said Helms. “We’re bringing in partners who are building circularity
into their product lines and manufacturing capabilities, and giving them an
option that is in line with future best practices.”
Added Scown: “We know there’s interest
at that level. Some countries have plans to charge hefty fees on plastic
products that rely on non-recycled material. That shift will provide a strong
financial incentive to move away from utilizing virgin resins and should drive
a lot of demand for recycled plastics.”
After infiltrating the market for
durable products like cars and electronics, the team hopes to expand PDKs into
shorter-lived, single-use goods such as packaging.
A full-circle future
As they forge plans for a commercial
launch, the scientists are also continuing their techno-economic collaboration
on the PDK production process. Although the cost of recycled PDK is already
projected to be competitively low, the scientists are working on additional
refinements to lower the cost of virgin PDK, so that companies are not deterred
by the initial investment price.
And true to form, the scientists are
working two steps ahead at the same time. Scown, who is also vice president for
Life-cycle, Economics & Agronomy at the Joint BioEnergy Institute (JBEI), and Helms are
collaborating with Jay Keasling, a leading synthetic biologist at Berkeley Lab
and UC Berkeley and CEO of JBEI, to design a process for producing PDK polymers
using microbe-made precursor ingredients. The process currently uses industrial
chemicals, but was initially designed with Keasling’s microbes in mind, thanks
to a serendipitous cross-disciplinary seminar.
“Shortly before we started the PDK
project, I was in a seminar where Jay was describing all the molecules that
they could make at JBEI with their engineered microbes,” said Helms. “And I got
very excited because I saw that some of those molecules were things that we put
in PDKs. Jay and I had a few chats, and we realized that nearly the entire
polymer could be made using plant material fermented by engineered microbes.”
“In the future, we’re going to bring in
that biological component, meaning that we can begin to understand the impacts
of transitioning from conventional feedstocks to unique and possibly advantaged
bio-based feedstocks that might be more sustainable long term on the basis of
energy, carbon, or water intensity of production and recycling,” Helms
continued.
“So, where we are now, this is the first
step of many, and I think we have a really long runway in front of us, which is
exciting.”
The Molecular Foundry is a Department of
Energy (DOE) Office of Science user facility that specializes in nanoscale
science. JBEI is a Bioenergy Research Center funded by DOE’s Office of Science.
The
Future Looks Bright for Infinitely Recyclable Plastic (lbl.gov)
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