“We’ve developed a product that is circular ánd climate adaptive.” – Interview with Eva Aarts and Wies van Lieshout, founders of Waterweg.


It may be 2020, but in the dredging and construction sector Eva Aarts (22) and Wies van Lieshout (26) still stand out as young women. Nevertheless, they can be found there regularly: in 2018 they won the Circular Challenge with their idea for water permeable tiles made from a waste stream of dredging. Now, two years later, they are well on their way with their startup Waterweg.

“There have been times where we walked on to a construction site and there were posters of naked women hanging all around,” they say while laughing. “There we were, having a cup of coffee with a couple of very manly men.” We also had a cup of coffee with Eva and Wies – not surrounded by posters but in the middle of samples, baking dredge and knee boots, in their production room.

Two birds with one stone

The two got to know each other during the Circular Challenge in 2018 in which they had to develop a circular product for the Delfland Water Board with a residual stream of dredging. “Dredging is mainly a problem in urban areas because it cannot be laid on the quay after it has been taken out of the water,” Aarts says, “It also takes a long time to take the dredge from the city to depots to process it there.”

Besides tackling this problem, the duo also wanted to tackle other problems in urban areas. “We soon found out that we could harden the dredge and asked ourselves: what can we do with this material?” van Lieshout continues. During a good brainstorming session, ideas such as cladding and street benches were thrown up, but the idea of water permeable tiles stuck.

The water permeable tile also offers a solution for excessive water in the city. “In the current situation, the water cannot sink into the ground because there are so many tiles blocking the way,” van Lieshout says, “but by making tiles through which the water can pass through, we relieve the sewers in times of heavy rainfall. In this way, we’ve connected two problems and developed a holistic product that is both climate adaptive and circular.”

Local application

Good idea of course, but how do you go from dredging to sidewalk tile? “We prefer to see dredging transported directly from the water by truck to a factory where it is mechanically dried,” van Lieshout explains. “Then you have a dry and granular material that we can sieve and grind into something very fine. It is then mixed with cement.”

This mixture then goes into a mould where it is pressed together. “That’s what you call compressed earth block technique,” van Lieshout continues, “which ensures that the tile remains in a solid form.” The last step is to let the tile dry and then it can be put out on the street. “Ideally, the tile should be used locally, in the same neighborhood as where the dredge came from.”


Putting it like that, it all sounds very easy. But there are actually quite a few challenges hidden in the process: “We don’t know everything either, and certainly in the beginning this sector was completely new to us.” Aarts says, “We really felt like rookies, walking in somewhere with a crazy idea and then people probably thought: what do they know anyway?”

But according to the two of them, that’s perhaps where their strength lies. “Because we have to question everything, we make everyone rethink the most mundane things.” van Lieshout says. “If we ask why things go the way they do, often the reaction is: yes, why does that actually work like that?”

And that creates room for change, although it requires determination to put it into practice. “We say quite easily: okay, how are we going to adjust this and who do we have to talk to for that,” Aarts goes on. “And even if something fails, we believe we can gain something valuable from it. We just want to prove that even with an ugly and filthy product like dredging you can make something cool.”

More than just talking

Ondernemers Eva Aarts en Wies van Lieshout

It is this mentality that makes people jump on board. “I think that our determination and energy is super important,” says Aarts, “we try to engage people in a certain mindset in order to get started with a new product. We don’t like that endless talking about problems and then doing nothing about it.” adds van Lieshout. “I love that you can create something beautiful with your own hands and that is meaningful at the same time. And by making something tangible, it’s easier for others to understand and more inspiring.”

“So we’re actually selling a vision and that’s how we try to excite people,” Aarts continues, “The two of us don’t possess all the knowledge, so we need input from others.” And for that BlueCity is the perfect place!

Building a network

Waterpasserende tegels waterweg

After winning the Circular Challenge, van Lieshout en Aarts established their startup Waterweg in BlueCity. “Of course without BlueCity we wouldn’t even have started this whole thing,” van Lieshout says, “and we know that there’s a community here that makes it easy to get in touch with useful contacts.”

“The BlueCity Lab is also very important for us, because it provides us with a place where we can test methods and materials, which is really great.” says Aarts “And besides that, it’s just really nice here too!” They find inspiration in the entrepreneurs around them, for example when the guys from Fruitleather talk about a certain drying technique. “That’s how we help each other out.”

Dream scenarios

“Our next step is the upscaling of the production process together with the Municipality of Rotterdam.” says van Lieshout, “We are going to transform 15 to 20 tons of dredge into tiles and then lay approximately two to three hundred square meters of water permeable paving.”

The two secretly also dream of bigger plans. “We would really love it if in the future all dredging is used for the creation of new products, from tiles to benches and cladding.” van Lieshout says, “And a partnership with HAY or IKEA to bring a product to the consumer market would be really cool too!” she concludes. 

BlueCity Circular Challenge

The BlueCity Circular Challenge offers established companies the opportunity to become acquainted with the circular economy by developing a scalable product from their own waste stream within six weeks. Participants are at the cradle of promising startups and innovations.

Does your organization have circular ambitions? Sign up for the next BlueCity Circular Challenge and turn your waste stream into a circular business case! Send an email to n.braamse@bluecity.nl or give Niels Braamse a call on 06 82719180.