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Celine’s Bachelor’s project was the cornerstone in a new waste-separation technology

It is important to remember the energy and wild ideas of the young engineering students, says the plastic separation company Plastix, who speak warmly about Celine Ballegaard Karlsen and her Bachelor’s project which was part of the Re-Plast research project.

There must be some mistake,” said Celine as she sat in front of her Mac in her small one-bedroom student apartment in Aarhus in early October last year.

She had gathered a vast amount of spectrum data using Aarhus University’s new hyperspectral camera, which had taken a number of images of different types of plastic on an assembly line, and now she had run all the data through a primary component analysis (PCA).

“The images show the light waves captured by the hyperspectral camera when the plastic samples are illuminated. A spectrographic analysis of these gives me a whole lot of curves on a graph. I sat and looked at the curves, but I simply couldn’t see any difference between them, so I tried to see a difference using a PCA analysis,” says Celine about her experiments.

And apparently, she could. Because the result she received was, to put it mildly, surprising.

Plastic, polymers, and recycling

Celine Ballegaard Karlsen was born and grew up in the Danish town of Grenå. She comes from a very traditional family and is the eldest of five sisters. Celine is dyslectic and she has been really bad at language subjects all her life. She can read well enough, but it takes a long time, and so today she gets the computer to read for her.

At primary school, she was very good at maths, but when the alphabet took over, things became more difficult for her. But she is practical and logical, and she has always liked science subjects, so she chose maths, physics and chemistry as her main subject line at upper secondary school. She also likes technology: a hobby she mentions that she inherited from her father, who is a molecular biologist.

The idea of the chemical engineering programme came to her quite early on, and she started on the Bachelor of Engineering programme in chemistry at Aarhus University in the summer of 2017.

On the fourth semester she had a course about polymers, and she found this very interesting.

“It wasn’t as process-technical as many of the other courses, and I liked that. And I met Associate Professor Mogens Hinge, who said that I could do my Bachelor’s project with him if I liked,” she says.

She continues,

“Plastic, polymers and recycling is an incredibly exciting area. We’re living at a time when we throw out huge amounts of plastic that we can’t recycle. In fact, we can only separate a small fraction for reuse, and I think it’s a shame that all these resources are just being incinerated. So it would be fantastic if I could contribute to something that might make a difference in the area.”

An important resource

This way of thinking struck a ray of hope for the future for Hans Axel Kristensen, CEO of the Lemvig-based cleantech company PLASTIX.

The company converts used fishing tackle into raw materials for plastics by washing, drying and melting plastic fibres from old fishing nets and rope, for example, into plastic granulate that can then be reused in new plastic.

“We’re delighted with our research collaboration with Aarhus University, and it’s been a real pleasure to see the extent to which engineering students have contributed to the project. It’s important to remember the energy and wild ideas of the young that exist among engineering students. They’re passionate, and it’s often students who create new synergies and set things in motion. They’re an important resource at every step of their education and they help to make important breakthroughs, like we’ve seen here,” says Hans Axel Kristensen.

He remembers very well the autumn of 2020, when Celine and researchers from Aarhus University presented the very exciting results of the Re-Plast project, and when it became clear to him and the rest of the team that they were on the verge of something entirely new in plastic separation.

“The technology we’ve developed in collaboration with the university is nothing short of a breakthrough for our ability to recycle plastics,” he says.

Learning about everything around us

Today, Celine is 24 years old and she is studying for an MSc in Engineering in Chemical Engineering and Biotechnology at Aarhus University’s Department of Biological and Chemical Engineering. She is working on her Master’s thesis on agricultural plastics with her supervisor, Mogens Hinge.

In her apartment at the “Dania” halls of residence there are two pictures, one showing the molecular structure of coffee and the other the molecular structure of chocolate. The pictures are almost identical, and they remind her that even minor changes in the building blocks of things can have enormous significance.

This also applies for plastics, which are often made up of chains of carbon and hydrogen atoms linked together in different ways.

“That’s really what makes chemistry so exciting. Learning about everything around us. Learning that everything is basically put together with the same building blocks, the same atoms, but in different ways so that things have very different applications,” she says.

Celine’s Bachelor’s project has been a significant scientific contribution to the article published by the team in the international journal Vibrational Spectroscopy and it has had a major impact on the experimental development of the methods to be implemented at industrial scale in 2022.

She is very pleased that her project ended as it did, even though it meant that she had far more work:

“The project was huge compared with the just 20 ECTS credits it had to fill,” she says, and continues:

“But it’s been very satisfactory. When I started, I had an idea that this might be realised in the real world at some time far in the future. I thought that the kind of research we’re doing at university wouldn’t be realised for many years. So, I’m very pleased that we can already start using the technology in industry. It’s been great to work with, and I’m proud of my contribution to solving this huge challenge.”

It is these tiny differences that the new camera technology can distinguish between. So far, the team behind the Re-Plast project now knows the difference between 12 different types of plastics, which together constitute virtually all household plastics and a number of high-performing plastics. But the research is not over yet. The project will continue, and before long the project partners expect to be able to differentiate further between types of polymer and various additives.