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Circular Plastics Challenge Targets rPET

Winners in the 2024 challenge used bottle geometry to improve recycling, deployed florescent tracer-based sorting, and turned stores into recycling centers.

Kate Bertrand Connolly 1, Freelance Writer

May 20, 2024

4 Min Read
Strong Bottle was first place winner
Top winner Strong Bottle reimagines the water bottle to improve recycling rates.Strong Bottle via Hillenbrand

At a Glance

  • Circular Plastics Challenge focused on increasing the supply of rPET.
  • First-place winner addressed the problem of PET bottles flattened during recycling.
  • Winners were announced at NPE2024 via a virtual showcase.

Hillenbrand, Net Impact, and Coca-Cola announced the winners of the second annual Circular Plastics Challenge, a global competition that builds awareness and promotes innovation in plastics sustainability and circularity.

A key goal of the annual challenge is to mobilize the next generation of plastics-industry leaders with a real-world circularity problem, enabling them to put their experience and classroom knowledge to work on solutions. Participants each year include undergraduates, graduate students, and professionals.

This year’s challenge focused on solutions that boost the supply of recycled PET aka rPET.

“As more companies commit to ambitious recycled content goals due to regulatory and consumer pressure to combat global plastic pollution, the supply of recycled PET is not keeping up with demand,” said Hilary Manzo, associate director of programs at Net Impact.

“According to a 2023 McKinsey & Co. report, from 2012 to 2022 rPET consumption increased roughly 4% per year, while supply only grew at around 1% per year over the same period,” she noted. Manzo moderated the finalist presentations and awards announcement for this year’s challenge in a virtual showcase broadcast from NPE2024, held May 6-10 in Orlando, FL.

The 2024 Circular Plastics Challenge generated 65 applications from 18 countries, up from 50 submissions from 10 countries in its inaugural year.

The submitted projects, which are at laboratory scale, ranged from reverse vending to extended producer responsibility (EPR) innovations. The challenge’s panel of judges included sustainability executives from Hillenbrand, Net Impact, and Coca-Cola; judging criteria include practicality and scalability.

The top three teams received awards of $10,000, $2,500, and $1,000, respectively.

Circular Plastics Challenge top winner details.

First-place honors in the 2024 challenge went to a reimagined PET beverage bottle dubbed the Strong Bottle, which features a novel geometry designed to boost recycling rates. The Strong Bottle team is based at Boise State University.

The second-place winner was EcoTrace, a technology that uses florescent-based markers and tracer-based sorting to improve PET’s recyclability. Third place went to rMarket, a platform for transforming retail locations into recycling centers.


The Strong Bottle team, led by Boise State graduate student Terra Miller-Cassman, undergraduate Taylor Fackrell, and mechanical engineering professor Aaron Smith, proposed a clever solution to the common problem of lightweight, single-use water bottles being flattened during the recycling process and consequently being improperly sorted.

With current PET water bottle shapes, the pressurized air-sorting technology at materials recovery/recycling facilities (MRFs) can blow flattened bottles into the paper recycling stream rather than properly diverting them to go with bulky plastic items. The flattened bottles contaminate the collected paper, and the paper/bottle mixture ends up in landfill.

This type of paper-stream contamination occurs so frequently that many municipalities have eliminated lightweight PET water bottles from their curbside recycling programs.

Strong Bottle features a new disposable water bottle shape that won’t flatten during recycling and could create a 15% increase in the PET collected.


The new shape features alternating spheres and cylinders. As compression force presses on the spheres, the load is distributed, reducing total compression force on the sides of the bottle and preventing flattening.

“Our team developed Strong Bottle to increase the supply of recycled PET,” said Miller-Cassman in her presentation at the NPE2024 showcase. “We have essentially redesigned the water bottle to make it universally recyclable.

“If the major beverage brands were to adopt the Strong Bottle design, it would influence widespread acceptance of lightweight bottles in municipal curbside recycling programs, and this would increase the amount of recycled PET by 400 million pounds per year for a total amount of 1.2 billion pounds per year in recycled PET bottles,” she added. “This is a 60% increase over the amount of recycled PET bottles that were captured in 2022.”

Strong Bottle uses the same amount (6 grams) of PET as an ultra-light-weight water bottle.

The Strong Bottle was developed as a drop-in solution for existing PET water bottles and designed to be manufactured using existing bottle-manufacturing methods.

Following the developmental stage, the Strong Bottle team plans to “manufacture a prototype by blowmolding the shape and gather feedback from customers in the beverage industry and run a pilot test with a material recovery facility,” Miller-Cassman said.

Although initial renderings show a grey bottle, the Strong Bottle prototype will be molded from clear PET.

The first-place winner in last year’s Circular Plastics Challenge was a startup, Ashaya, that turns post-consumer multilayer plastic packaging into recycled sunglasses and other products. It subsequently appeared on Shark Tank India where the company received funding from the H&M Foundation and Social Alpha in India to continue development and commercialization.

A video of this year’s finalist presentations appears below.

About the Author(s)

Kate Bertrand Connolly 1

Freelance Writer

Kate Bertrand Connolly has been covering innovations, trends, and technologies in packaging, branding, and business since 1981.

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