Development of a brush with a core made of wasted dolly rope

The Circular Plastics research group at NHL Stenden University of Applied Sciences aims to contribute to a sustainable society by making smarter use of residual waste flows of plastic materials and products. The Dolly Rope project shows that cooperation with various stakeholders is essential for this.

"The question is what to do with all that dolly rope, since there is no good processing method available yet."

Dolly rope is a product used in bottom fishing, where a fishing cutter or trawler pulls trawls across the bottom of the sea. To prevent damage and wear to the nets, dolly rope is attached to the trawl nets. Dolly rope consists of orange or blue threads of polyethylene, and is attached in bunches under the nets. In Europe, about 100,000 kilos of dolly rope are consumed each year, 40,000 kilos of which are consumed by Dutch fishermen (Strietman, 2021). Dolly rope loses its effect after about two months after which it is replaced. The discarded dolly rope is collected in the harbor to prevent it from ending up in the sea. However, the question is what to do with all that dolly rope, since there is no good processing method available yet. 

Therefore, KIMO (a Norwegian abbreviation that stands for "Kommunernes Internationale Miljøorganisation"), an association of coastal municipalities fighting against marine pollution, asked the Circular Plastics research group to find a suitable application for discarded dolly rope. This was a kind of ‘chicken and egg situation’, because when developing a suitable application for the residual material, you first need to know what this residual flow looks like exactly. At the same time, the way the residual stream is processed still had to be developed, and the design of the final product could influence the way the raw material (the dolly rope) would be processed. 

"In this way, a truly circular product is created, starting (as dolly rope) and ending (as a scrub brush) on the fishing boat."

The development of a prototype of a possible final product was a way to get out of this impasse. Therefore, an initial concept development phase was carried out by students from the Industrial Product Design course from Hanze University of Applied Sciences and students from the Circular Plastics minor at NHL Stenden. During this process, the dolly rope was recycled, after which the processed material was used to design a scrubbing brush for fishing boats. In this way, a truly circular product is created, starting (as dolly rope) and ending (as a scrub brush) on the fishing boat. Through this cyclical approach, the value of the dolly rope waste becomes clear to the fishermen, giving them additional motivation to continue collecting the dolly rope separately. To actually manufacture this brush, Jobo Borstelfabriek was involved in the project. The model of the scrubbing brush resulted into a further development of the concept together with this company in cooperation with Bek & Verburg - a maritime waste processor - and Groningen Seaports.

Since the development of a mold for the relatively large scrub brush was quite costly, it was finally decided to develop a nail brush, since a smaller mold could be used for this. Ultimately, within the project, the entire process of waste collection, processing, and application in a new injection molded product was developed. This demonstrated that dolly rope, if properly processed, can be used for the serial production of relatively high quality products. Further development of the recycling process will be taken up by Bek & Verburg and a recycler.

Reflecting on the development of the overall value chain (see Figure 1), we see that an initial design of a possible final product helped to define the overall value chain. This allowed the necessary stakeholders to be identified, and the impasse of an equation with too many unknowns to be resolved.

"All in all, the dolly rope shows that effective cooperation between government, knowledge institutions and business is required to take concrete steps towards a truly circular economy."

Looking at the role of the different actors during this process, we see that the overall process was driven by a semi-governmental organization (KIMO). NHL Stenden played an important role as a driver of possible promising solutions, and as an intermediary between the different organizations. This is partly possible because the university can focus on societal challenges where it is not yet exactly clear how the value chain fits together, and thus will not be picked up by industry on its own. The added value for Jobo Borstelfabriek is to be able to sell products with a 'story'. But it is expected that the biggest benefits will ultimately be to the waste processor, because the dolly rope waste can be processed more easily, increasing the value of the raw waste material. In addition, the recycler has an additional material stream to process and market. When the entire process is successfully completed, it adds value throughout the value chain, as visualized in Figure 2. All in all, the dolly rope shows that effective cooperation between government, knowledge institutions and business is required to take concrete steps towards a truly circular economy.