July 1, 2019

Co-creation in the Green Idea Café

During the Green Idea Café on 17 June 2019 in the Scheltema, residents heard more about the new citizen science project aimed at investigating plastic in the canals of Leiden. Together with the team they also brainstormed about various aspects of the project, such as the research questions and the method, which yielded many interesting ideas.

Plastic not so fantastic

Several team members are working together in the research that resulted from a call for questions among residents and scientists. For example, ecotoxicologist Martina Vijver of the Centre for Environmental Sciences (CML) talked about the plastic problem. Although plastic has many advantages, it is also difficult to recycle and only 5 to 9 per cent is actually recycled. The rest is burned, releasing harmful substances or ends up in the environment where it hardly degrades, Vijver emphasized.


We know how the plastic ends up in the water and eventually in the sea, but mainly from models according to Anna Schwarz, researcher circular economics at TNO. To verify these models we need data about the actual transport, how much is where and how is this influenced by certain events such as the 3 October festival, the market and the weather. In order to get a picture of plastic transport in the water in the Leiden region, residents and researchers can collect data together with the app CrowdWater. Tim van Emmerik, hydrologist at Wageningen University, explained why the app was created and how it works.

Plastic nests

The project wants to link up with existing initiatives, as a lot is already happening in the field of plastic pollution. For example, Liselotte Rambonnet, project manager Citizen Science Lab, shared a dozen local initiatives such as 'Grondstofjutters' where beach visitors can receive a cup of coffee in exchange for plastic waste they collected from the beach, and the Great Bubble Barrier, an initiative to capture plastics from the water. And not only people, but also animals help to collect waste from the environment. Including the coot, the study object of master student biology Auke-Florian Hiemstra. Hiemstra is curious about the relationship between the natural and plastic material and whether the coots might have a preference. Possibly the waste is also a good indication for the pollution in the vicinity of the nest. In this way, you might be able to find out the source of the waste, like the biscuit packaging from a terrace near a nest.

Brainstorm sessions

During the second part of the evening, visitors brainstormed about different aspects of the project together with the team members.

Plastic in sediment

The first session with Vijver dealt with other relevant questions about plastic in the Leiden region. Although not all of them can be dealt with within this project, they may also be questions that can be studied in a follow-up project. This yielded several interesting questions such as: how much plastic is in the bottom of the ditch and does it differ per sediment such as sand and clay and what is the most effective way to reduce plastic waste for households and businesses? People could also try out the CrowdWater app and share feedback. During this pilot, a total of thirteen pieces of plastic were observed at a distance of ten metres near the Oude Vest. Naming the type of plastic proved to be difficult, and also estimating the distance. In addition to this, there was no option to indicate that the plastic had been removed from the environment. These remarks will be taken into account as much as possible in future updates.


Visitors also brainstormed with researcher Anne Land-Zandstra of the Citizen Science Lab about which target groups can be reached with this project. These are target groups such as: (residential) boat owners, fishermen, primary school children, residents around the canals and dog owners. In addition, a very important target group is the already active litter collectors. It is useful to connect with this group of active volunteers and to indicate that collecting data is really necessary to tackle the problem at the source. And although children are an important target group, the app may still be too difficult for them at the moment, just as it is for illiterate people. Regarding ways to reach the target groups, ideas were shared with project leader Matthijs Begheyn of the Citizen Science Lab. For example, the litter collectors can be reached via neighbourhood associations and fishermen and dog owners via signs at the canal.


The aim of this project is not only to obtain new knowledge for science and to publish results but also to create awareness about the importance of science for the future of our society.