Making data more accurate and success more visible – sensor experiments developed waste management at schools

The need for a measurement experiment arose from the challenges encountered in reporting. Learning and developing a sustainable lifestyle, including effective sorting, in schools is an important goal for Espoo, and there is in monitoring the progress of this goal. Previously, there was only calculated data on the amount of waste generated in schools – mathematically inferred figures based on container volumes and averages. We wanted to refine the data so that there is just the right number of collection containers for different waste components at schools and they are emptied at appropriate intervals.

“With this study, we wanted to gain certainty for sorting reporting, as well as get more accurate information on how much waste is generated, how efficiently sorting containers are used and how accurate the assumptions of our existing data are,” says Mia Johansson, Project Manager of Closed Plastic Circle – from Pilots into Practice.

Sensors purchased from Wastebook(external link, opens in a new window) act on a sonar-like principle and measure the surface level of the waste container, that is, the filling rate of the waste container.  The sensors are attached to the underside of the waste container lid. The sensors also register their own inclination, which means that they notice possible overfilling situations where the waste container lid does not close completely.

“This pilot is a good example of how the measurement of waste data using digital solutions can be utilised to make recycling more efficient. For Wastebook, the joint pilot with the City of Espoo has been very interesting, and it has attracted interest among the stakeholders included in the project, ”says Mikko Ahokas, CEO of Wastebook.

The primary schools included in the measurement experiment were Aarnivalkean koulu, Ruusutorpan koulu and Karhusuon koulu. Schools of different sizes from different parts of Espoo were selected for the experiment.

In the light of the results received, school waste management appears largely quite efficient – the filling rates of the containers are high at the time of emptying. Overfilling occurred occasionally, so in some situations it may be possible to monitor whether the emptying interval of some containers should be slightly increased. The school average of the filling rates of mixed waste containers varied between 75–84%. The school average of the filling rates of plastic waste containers was 36–94%. The number of containers was found to be suitable in the experiment.

The volume of waste accumulated varied widely from month to month. For example, before Christmas, the amount of waste generated was clearly higher, as Christmas cleaning was carried out at schools. Christmas holidays, on the other hand, were visible as a decrease in the amount of mixed waste, but plastic collection peaked during the break – it turned out that kitchens usually clear out their cabinets then.

The Aarnivalkean koulu primary school dominated the sorting aspect of the experiment, as the most amount of plastic waste was collected at the school, both in absolute terms and in proportion to the number of pupils. Aarnivalkean koulu also produced the least mixed waste. Aarnivalkean koulu was one of the first schools in Espoo to start sorting all waste components in 2019, so one reason for the school’s good result is probably persistent practising and experience gained through it.

The successfulness of sorting is not only dependent on appropriate sorting containers but also high sorting activity and good sorting skills. After the measurement experiment, determined sustainability education continues at schools.

“I personally consider sorting to be very important, and I have been trying to promote it at our school for a long time. This experiment and the results obtained from it serve as a good tool for going through and maintaining sorting. It was nice to be able to participate in the experiment,” says Mimmu Hellsten, Head Teacher of the Karhusuon koulu primary school.

“The happy story of growth and learning consists of daily work with children and young people at our schools. This includes actions such as reducing food waste, teaching recycling and nature education. I would like to thank all the schools that participated in the experiment: the primary schools Aarnivalkean koulu, Karhusuon koulu and Ruusutorpan koulu”, says Director of Basic Education Juha Nurmi.