Millions of tonnes of waste end up in the world’s oceans every year. Plastics account for the largest share, decaying very slowly and threatening not only marine life and ecosystems, but also our health. Students at ETH Zurich have been working on finding technical solutions to alleviate this problem since 2019 as part of the Autonomous River Cleanup (ARC) initiative. The reason for the focus on rivers is primarily practical in nature. When plastic waste reaches the sea, it becomes much more difficult, if not impossible, to remove effectively, as it spreads widely and breaks down into smaller and smaller particles. “In rivers, the waste tends to be more concentrated and intact, which can make it easier to remove,” explains Fidel Esquivel, ETH Master’s student in Robotics, Systems and Control and a founding member of the ARC project.
Aiming for an efficient and intelligent system
The students have analysed various technologies in the laboratory, which they will now test for the first time in a realistic environment and in interaction with each other. The test facility is located on the Limmat, alongside Zurich’s Platzspitz park. Up until the end of August, the students will examine the following three steps that are central to waste removal: concentration in one place, collection and sorting. In addition, they also aim to assess the quantity and composition of waste in the river by means of cameras at the Walchebrücke. The group will test various approaches for concentrating waste in one place, some of which will be combined – including a floating barrier and a barrier made of air bubbles. The students will use a conveyor belt to collect the material on the test platform, working to determine its optimal alignment. A robotic arm with a camera will separate the waste according to material, with biomass returned to the water. This will show whether the specially programmed deep learning algorithms recognise the objects correctly. Among other things, students will use floating GPS trackers to investigate the routes travelled by the waste. The results of the tests will subsequently be published on the project website.
The ARC project aims to increase knowledge in various areas, including how to quantify waste in bodies of water. The amount of plastic and forms of waste that end up in rivers and oceans is not precisely known, and various studies have reached very different estimates. In addition, the on-site analysis and sorting of waste is a new approach. “As a first step, we want to make sure that biomass can return to the river so that the ecosystem is affected as little as possible. But in the longer term, we aim to separate the waste by material and even by different types of plastic to be able to recycle it,” explains Joachim Schaeffer, a Master’s student in Energy Science and Technology at ETH, who is leading the tests on the Limmat. The ultimate goal is to ensure that the whole system is as energy-efficient and intelligent as possible. This would enable the intensity of the air bubbles and the speed of the conveyor belt to be automatically adapted to suit the detected amount of waste, as Schaeffer explains.
