Every day the Rhine washes tons of garbage into the North Sea. Together with citizen scientists, researchers collected, weighed and categorized waste from the Rhine for more than a year. A total of more than 17,500 individual items with a total weight of almost two tons ended up in a floating waste trap in Cologne used for the study within a year. Extrapolated to the total flow volume, this corresponds to around 3,000 to 4,700 tons of waste per year. More than half of the items collected came from private individuals, around 70 percent were made of plastic. The New Year’s Eve fireworks also left their mark.
If rubbish is not disposed of properly, it often ends up in the environment and reaches the sea via rivers. As one of the largest rivers in Europe, the Rhine transports large amounts of waste into the North Sea and thus into the Wadden Sea nature reserve. However, exactly how much was unclear until now. For most previous estimates, the amount of waste was only recorded on individual days and then extrapolated over the entire year.
Waste collected and analyzed
A team led by Nina Gnann from the Eberhard Karls University of Tübingen has been continuously fishing and analyzing garbage from the Rhine for over 16 months. To do this, the researchers used a floating garbage trap called “Rheinkrake”, which is anchored in Cologne and belongs to the non-profit association KRAKE (Cologne Rhine Clean-Up Command Unit) eV. The trap catches waste floating on the surface of the water and up to 80 centimeters below. It filters around 0.08 percent of the total flow.
Together with volunteers, the researchers analyzed what types of waste ended up in the trap over the entire observation period. All pieces of trash that were at least one centimeter in size were collected, weighed and categorized. Within one year, from November 2022 to November 2023, 17,523 individual parts with a total weight of 1,955 kilograms were collected. Extrapolated to the entire width of the Rhine, that’s around 3,000 to 4,700 tons of waste per year – more than 250 times as much as previous estimates had assumed.
“The amount of waste fluctuated by a factor of 41 and was higher in times of increasing runoff volumes,” reports the research team. During times when the Rhine was in flood and also picked up objects lying on the bank, the trap contained significantly more waste than in weeks when the water level was low. In order to estimate the amount of waste throughout the year, researchers believe that individual collection days are too unreliable.
Composition of garbage
The analysis of the waste revealed the different dimensions of the waste problem: “We found that private consumers are the largest source of macro-waste at 56.4 percent,” reports the team. This includes food and drink packaging and cigarette butts. Industrial waste made up 5.9 percent of the waste, while 1.6 percent came from transport, infrastructure and buildings. The researchers were unable to clearly identify the remaining items.
Almost 70 percent of the items collected were made of plastic – from packaging to toys to flower pots. However, measured by weight, plastic waste only accounted for 14.8 percent. “This underlines the relevance of non-plastic waste,” say Gnann and her team. These include wood, glass, ceramics, metals, cardboard and paper as well as textiles. Fireworks waste formed a separate category: At the turn of the year 2022/2023, 1943 remains of rockets etc. ended up in the garbage trap, including mainly wooden rocket rods and plastic caps. “Apart from New Year’s Eve, we were unable to find a connection between a cultural event and the amount or type of waste,” report the researchers.
By breaking down what types of waste end up in the Rhine, the study can help to specifically address the problems. The survey can also help to better assess the success of waste prevention strategies in the future.
Source: Nina Gnann (Eberhard Karls University of Tübingen) et al., Communications Earth & Environment, doi: 10.1038/s44458-025-00007-5