The international recycling company Tönsmeier (Porta Westfalica, Germany) became a partner of Germany’s World Wide Fund (WWF Deutschland) for Nature in September 2015, and since then has been working to rid the Baltic Sea of so-called ghost nets, abandoned fishing nets made of plastic. Environmentally friendly recycling of these polypropylene and polyamide (nylon) ghost nets is being tested, and Vecoplan AG (Bad Marienberg, Germany), which develops shredding, conveying and processing machinery and plants, was brought in to create an optimal process for transporting, processing and recycling the salvaged material. The results of initial tests have been positive, said Vecoplan
The Baltic Sea is relatively small, making it ideal for the development of a process for salvaging, processing and recycling ghost nets; that knowledge can then be transferred to larger bodies of water. Tönsmeier sought the support of Vecoplan AG for processing the PP and PA nets.
Vecoplan has been developing and manufacturing machinery and systems for resource recovery and recycling management for almost 50 years. “Our task was to find options for the material recycling of salvaged nets in our own technology center,” said Vecoplan Project Manager Ulf Kramer.
In addition to the polymers, the project partners salvaged some 450 kilos of material entangled in the nets, including 14 kilos of scrap metal, such as anchors, chains and pipes; 37 kilos of stones and boulders; 21 kilos of mussels; 4 kilos of textiles and shoes; and 20 kilos of wood. The material was then manually sorted into course nets, fine gill nets and fixed ropes.
The pre-sorted groups were subjected to various tests to determine the most effective processing steps. “The groups were shredded with no problems,” said Kramer. Vecoplan used the VAZ1600 M XL single-shaft shredder with a 110-kW HiTorc drive for this important first step of the process. The machine was configured with a U-rotor and a filter diameter of 20 mm.
“We equipped the VAZ like this because we had already run tests in the technology center using old, discarded nets, and we were also able to draw on our own experience,” Kramer added.
Because heavy materials such as the lead weights, mud and sand fall to the bottom, the PP and PA6 (nylon) can be skimmed off the water surface and conveyed separately to the washing process after a second water bath. The shredded material is then “dewatered” and separated by density, and taken to a production plant, where a drying process began. Kramer noted: “Following the tests, successful washing results were visually observed, and the purity values are now being analyzed in detail by various universities in their laboratories.”
The recycling and material reclaiming of the plastic fibers in the process are still being tested. “In my doctoral thesis, which is based on these experiments, the process is described from the point of view of economics and ecology,” said Falk Schneider, a University of Bath doctoral candidate, who is providing scientific support for the project on behalf of WWF. “We now know that it is possible to recycle ghost nets, but the question is, how economically viable is it? Detailed answers to this question will soon be available.”
Flip through this slide show to see how the process turned this ghost net into a pretty darn good-looking material. All images are courtesy Vecoplan.