‘Waste from waste’ Becomes Cool Bench

Bottom ash contains more useful raw materials than some people realise. You can even make designer benches with it. Student Carissa ten Tije knows all about it. With her own Twence bottom-ash bench, she has been nominated for the René Smeets Award, which will be awarded on 19 October during the Dutch Design Week.


What can you do with bottom ash?
Carissa ten Tije came to Twence to request bottom ash for her graduation project at the Eindhoven Design Academy. She wanted to research if this by-product from waste incineration could be reused in other ways. She came up with the idea to reuse bottom ash when she took out a bag of rubbish and wondered what happens to it. 'When I read that the rubbish is incinerated in order to generate energy, I thought that was a wonderful idea. But what happens with the waste from the waste that is left after that? It turned out that bottom ash was seeing some use already, for instance in paving, glazing, and as a mixing granulate. But there are more materials in it than you might think, such as precious metals, glass, plastic, or textile. I wanted to find out if there might be broader applications for bottom ash.'

A Bench Made of Twence Bottom Ash
The bottom ash is washed and immobilised in cement. Next, a protective layer is added. The end result is a designer bench made with Twence bottom ash. The legs are made of a very coarse grain, while the horizontal surface is made with a finer grain of bottom ash. You can look at the legs as a puzzle; you can see all kinds of materials from the waste in it. Carissa: 'It would be great if this circular product was used more often, for instance in public furniture. Put a rubbish bin next to it, and the circle will be completed.'

Bottom Ash as a Raw Material
Bottom ash is what is left after incinerating non-reusable materials, and it's an important raw material. It can be used as a replacement for scarce materials, such as sand and gravel. Twence focuses on reusing materials to stimulate the circular economy. The use of bottom ash, rather than the mining of new raw materials, is an important example of this.