So far, many recyclable materials still end up in residual waste. Researchers examined households in Stuttgart to find out why this is and how it could be changed. The field test showed that if garbage ends up in the wrong bin, it is often due to a lack of motivation. If you educate people about what the whole thing is for and what specific benefits it brings to the environment, waste separation will work better. In the field test, such information reduced the error rate by 70 percent.
Whether plastic, metal or electronic waste: According to the UN environmental program UNEP, more than two billion tons of waste are generated worldwide every year – and the trend is rising. Humanity is now releasing so many synthetic substances that it is endangering the stability of the Earth system – the planetary limit has been exceeded, as a study in 2022 determined. “Waste systems are already struggling with inefficiency, limited capacities and environmental damage,” explain Eva Pawelczyk and her colleagues from the University of Hohenheim. “Without quick action, these problems will continue to intensify.”
This makes it all the more important to recycle our waste products as well and completely as possible. Household waste plays a key role in this. Germany alone generates around 450 kilograms of waste per household per year. In order to be able to recycle this waste better, we have waste separation: organic waste, glass, paper and packaging are each collected and disposed of separately – actually. In practice, however, a large proportion of waste ends up where it doesn’t belong. When it comes to organic waste, it is estimated that around 40 percent of the waste ends up in the residual waste instead of the brown bin. But plastic, glass and other recyclable materials are often disposed of incorrectly.
A good 100 households in the garbage test
The problem: The often ridiculed waste separation can only work well and relieve the burden on the environment if the recyclables end up in the right bin. But why doesn’t this happen so often? Pawelczyk and her colleagues have now examined this in more detail. To do this, the researchers accompanied 102 households in Stuttgart in a field experiment twice for one week each. All participants collected their waste in three separate categories: residual waste, organic waste and plastic. After each garbage collection, the researchers analyzed this waste in the laboratory and systematically recorded incorrectly separated garbage.
Half of the test households received an information flyer after one week. However, this brochure did not contain any of the usual instructions for waste separation. Instead, she explained in simple images and text why waste separation is important: For example, because recycling plastic products saves energy and reduces CO2 emissions. Or that correctly separated organic waste becomes valuable compost that nourishes the soil and helps reduce greenhouse gases.
Decrease in incorrectly disposed waste by 70 percent
It turned out: “In the first survey period we documented a total of 3,791 sorting errors,” reports Pawelczyk. “Incorrect disposal of residual waste occurred particularly frequently. This shows that even in regions with well-functioning recycling structures, many households have problems with correct waste separation.” Contrary to popular belief, there were no significant differences between households in wealthier areas or in neighborhoods with lower-income populations. “The socio-economic environment is therefore not a decisive factor for incorrect waste separation,” writes the team.
The results of the second week – the time after the flyer was distributed – demonstrated how the error rate can be reduced. In households without this information brochure, the number of incorrectly separated waste had hardly changed. In the households that received an information flyer, however, the error rate fell significantly: from an average of 45.5 to 13.8 incorrectly disposed waste items per household. “That’s a decrease of around 70 percent,” says Pawelczyk. “Our results show that even simple and inexpensive information measures can make a noticeable difference. The key to better waste separation is to make the population aware of the direct benefits for society and the environment.”
Source: University of Hohenheim; Specialist article: Journal of Environmental Management, doi: 10.1016/j.jenvman.2026.129111