TKI Project: An alternative to plastic produced from unused organic waste streams

Producing an alternative to plastic can, on paper, be done entirely from wastewater streams, but how do you ensure that the necessary bacteria give the maximum output in relatively unusual conditions? That was the research question of Ángel Estévez Alonso, now a doctor. After an unexpected eureka moment, he managed to take his inventions as far as pilot-scale production. For NWP member Paques Biomaterials, they are helping move towards world production of a new plastic substitute.

A new raw material production in the making

The fact that the use of plastic brings with it several a few problems is now clear. But finding concrete solutions to these plastic problems is not yet easy, given how diverse the plastic group is. PHA - polyhydroxyalkanoate - seems a promising substance due to its natural production and easy biodegradation in nature. It is an attractive material because it can be derived from municipal sludge, a residual stream from wastewater treatment plants. "PHA is a kind of bacterial fat. Under certain conditions, the bacteria store excess raw materials in their cells," said Estévez Alonso. The long chains they make form towards processing a biological alternative to plastics. But turning wastewater treatment plants into production sites is not easy. Conditions vary across treatment plants and from day to day. So, it was quite a challenge for PhD student Ángel Estévez Alonso to boost the production of this alternative to plastic with the resources available.

Eureka moment

"For us, the production of PHA from residual streams started in Delft, in collaboration with Paques," explains René Rozendal, Managing Director at Paques Biomaterials. "There they saw the potential of PHA as a unique plastic substitute." In parallel, the Dutch Water Boards worked together in the PHArio project to extract the material from municipal wastewater treatment plants. Eventually, it even led to the construction of a joint demonstration plant in Dordrecht and the creation of a new research theme at Wetsus, an NWP member, called Biopolymers from water. Estévez Alonso's research was one of the first two projects that focused on extracting more PHA from water treatment. Estévez Alonso says that "For me, the challenge was in increasing PHA production. In the current way of treating wastewater, the bacteria know how to make some of the substance, but we wanted to convert 60% of the bacterial weight into PHA so that we can produce more material and demonstrate the properties and uses of the substance at a larger scale."

We wanted to convert 60% of the bacterial weight into PHA so that we could produce more material and demonstrate the properties and uses of the substance at a larger scale.

Dr. Ángel Estévez Alonso

Researcher at Wetsus

Parameters such as temperature and acidity naturally influence the behaviour of the microbial critters but, unsurprisingly, the PhD student stumbled upon his very own eureka moment. "When a student in the lab showed me how things were going, one of the substances we used in the process was missing. It was an oversight, and I didn't attach too much importance to it and decided to use calcium hydroxide instead of potassium hydroxide. I thought it was just another base material. But to everyone's surprise, the bacteria suddenly produced three times as much PHA as usual!" A wonderful find to bring the PHA to the level needed to test at the pilot scale.

Producing an alternative to plastic

Impact

"Ángel's work is relevant to Paques Biomaterials for the production of Caleyda, a PHA product," states Rozendal. "By understanding how PHA forms in bacteria, we can make a product more efficiently. And in doing so not only generate less waste and use less energy, but also further facilitate the downstream process."

By understanding how PHA forms in bacteria, we can make a product more efficiently. And in doing so not only generate less waste and use less energy, but also further facilitate the downstream process.

René Rozendal

Managing Director at Paques Biomaterials

And so, the technology is already being successfully deployed, with a pilot plant in Leeuwarden in 2020 successfully using discoveries from the research to produce PHA. Estévez Alonso says that "It was great to see the research in the context of a larger scale. The value of the research quickly became clear." As is often seen, a research collaboration like this can turn an idea into reality.

Rozendal is enthusiastic. "It was a valuable and fun collaboration. To scale up further projects, we need even more knowledge, but Ángel's successor – Yizhou Xing – will be important in this." Meanwhile, the production of Caleyda continues steadily at demo scale and Paques Biomaterials is working towards taking the commercial investment decision in 2025 for the first full-scale plant. And Xing is going to find out exactly what mechanism triggers the calcium hydroxide magic so that it can also be deployed on a large scale.