Be it plates, pots or glasses – hardly anyone can do their daily washing up without a kitchen sponge. But while it removes fat and food residue, it releases tiny plastic particles. Researchers have now examined how much of it in more detail. The result: Although measurable amounts of microplastics end up in the environment, the majority of the environmental pollution occurs elsewhere.
If you don’t have a dishwasher, you often use the kitchen sponge several times a day. The porous helpers are put under a lot of strain – and lose material over time. How much microplastic is released and what consequences this has for the environment has so far hardly been investigated
Microplastics from the dishwashing sponge
A research team led by Leandra Hamann from the University of Bonn has now systematically analyzed this for the first time. The aim of the study was to quantify the release of microplastics under the most realistic usage conditions possible and to evaluate the resulting environmental impacts using a life cycle assessment (LCA). To do this, the researchers combined citizen science with laboratory experiments. Volunteers in different households in Germany used one of three different types of sponges in their everyday lives and documented their use. By involving real users in this way, typical dishwashing habits and stress levels can be mapped much better than in pure laboratory studies.
To determine material loss, the sponges were weighed before and after use. In addition, controlled laboratory tests were used: an automated test machine (“SpongeBot”) simulated the mechanical stress during dishwashing, thus allowing comparable measurements under standardized conditions.
Several grams per person per year
The result: All types of kitchen sponges examined lose material during use and thereby release microplastics. Depending on the sponge type, the annual release is between around 0.68 and 4.21 grams of microplastics per person per year, as Hamann and his colleagues determined. Sponges with a lower plastic content release significantly less microplastics. Although the amount per capita appears low, when extrapolated to a national level, relevant amounts can be achieved – for example, up to 355 tons of microplastics per year if a certain type of sponge were used across the board in Germany. Although a large proportion of these particles are retained in sewage treatment plants, several tons of microplastics end up in waterways or soil every year.
Overall, however, the analysis showed that it is not the release of microplastics itself, but rather the water consumption when washing dishes by hand that accounts for the largest share of the environmental impact. 85 to 97 percent of the environmental footprint is due to water consumption. “Water use overshadows all other influences,” the team writes. “As a result, the advantage is that sponges clean more efficiently, thereby reducing the amount of water required.”
This results in several approaches to reducing the environmental impact of dishwashing. The most important thing is to use water sparingly, as this has the greatest influence on the overall balance. In addition, sponges with a lower plastic content can help reduce the release of microplastics. Longer use of the sponges also has a positive effect because it reduces overall resource consumption.
Source: University of Bonn; Specialist article: Environmental Advances, doi: 10.1126/science.adz9467