Diaper Recycling: Progress Even Among the Market Leader
Used diapers account for a very large portion of our waste, and to date, no economically viable recycling process has been established. In the Encycling project, the NMI team led by Dr. Anne Zeck and Dr. Simon Straß developed an enzymatic process that was successfully applied to diapers from various manufacturers. Further research was needed for the products of the market leader. Thanks to a grant from the foundation “Umwelt und neue Energien”, administered by Frankfurter Sparkasse, this issue could be further addressed in a follow-up project.
The grant enabled the NMI to conduct a master’s thesis on the topic. Laura Gorn, a student at the University of Tübingen, worked on the project at the institute.
Why doesn’t enzymatic degradation work for some diapers?
The first step was to understand why the method developed at Encycling did not work for the market leader. “We started with the hypothesis of chemical cross-linking caused by citric acid. The various experiments confirmed our suspicion,” explains Anne Zeck.
The Solution: An Intermediate Step Before Cellulose Degradation
The next step was to search for a combination of enzymes capable of breaking down both the cross-links and the cellulose fibers. Unfortunately, no solution was found for this; these cross-links make it extremely difficult for enzymes to gain access. Nevertheless, a small but important breakthrough was achieved as part of the master’s thesis. “We were able to establish a chemo-enzymatic process in which the cross-linking is first broken down chemically, allowing the cellulose to be subsequently degraded by enzymes,” said Anne Zeck.
This alkaline—that is, chemical—pretreatment is fundamentally economically viable. Conventional dishwashing detergents, which also operate under these conditions, serve as a model for this approach.
Seeking partners in mechanical engineering for the next step toward practical application
In theory, methods for recycling diapers are already known. However, they have not yet been applied on a large scale. For the NMI’s approach to be put into practice, several development steps are still necessary. To this end, Anne Zeck and her team are seeking partners in the fields of mechanical engineering and by-product management to specifically utilize the cellulose degradation products.
Many thanks to the foundation “Umwelt und neue Energien”, whose funding has made this next step possible, and of course to the Frankfurter Sparkasse for facilitating and handling the process!
Learn more about research on diaper recycling at the NMI on the Encycling projectpage and in the press release dated May 9, 2025.
