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Using bottom ash

Bottom ash is what is left over after incinerating waste. Once it is stripped of metals and 'washed', this can be used as a raw material in e.g. new roads or in products.

What is bottom ash?

Non-recyclable residual waste is incinerated at our waste-to-energy plant. We produce heat, steam and electricity during this incineration process. Bottom ash is what remains after incineration. We filter out the metals and reuse them. This bottom ash is used as a new raw material.

The use of bottom ash is a fine example of a circular economy. There is no such thing as waste in a circular economy: everything is reused and brought back into the cycle. We have not gotten that far in the world yet, but by producing new raw materials Twence aims to make a significant contribution to this ambition.

What do we use bottom ash for?

Bottom ash can be used in a variety of ways. A major sales market is civil engineering and road construction. Bottom ash can serve as a foundation in the construction of new roads. This means that fewer primary raw materials such as sand and gravel are needed and we avoid depleting large sand and gravel extraction areas. Bottom ash can also be used as a sealing layer for soil, for landfill and as a new raw material for products. Think in terms of concrete clinkers, kerb stones or outdoor furniture in public spaces.

We have already used our bottom ash in these

We are continually exploring new opportunities. For instance, there are more and more opportunities for soil substitutes and increased reuse of metals and non-metal raw materials. Here are a few practical examples of our applications.

Sustainable concrete clinker

At the request of Volvo garage Harrie Arendsen in Hengelo, we developed a concrete clinker together with Renewi and Morssinkhof in which bottom ash was used. The metal-free bottom ash was converted at Renewi into sand and gravel substitutes as a readily usable building material. The sand and gravel substitutes were sent to Morssinkhof Group for the actual production of the clinkers.

Volvo garage Harrie Arendsen has used these clinkers in their fully sustainable new building. By doing this, we have been able to close the regional cycle with our partners.

Bottom ash as a top layer

A new solar park is being built on top of our former landfill site 't Rikkerink in Ambt Delden. For its construction, we first covered it with a sealing layer. We used our own bottom ash to do this. We will explain how and why on this page.

Circular Bicycle Path

The first fully circular cycle path in Twente is located between Denekamp and Nordhorn. The cycle path was built by Abbink Boekelo Wegenbouw using Ecofalt, a sustainable alternative to asphalt. The newly developed foundation is made up of recycled rubble provided by Twee “R” Recycling Groep and bottom ash from Twence. This means that no new gravel and sand have been used. We will explain how we go about this and why on this page.

From bottom ash to sustainable concrete clinker

From bottom ash to raw material

Bottom ash remains after incineration. We extract practically all metals and non-metals in the bottom ash processing facility. We do this by means of various magnetic, sifting and separation techniques. Selection is done on the basis of size and weight. Since we use an in-house developed 'semi-dry' system during the incineration process, we are able to recover more than 90% of all metal granules larger than 2 mm. This places us among the world leaders in this field. By using this system, we minimise the oxidation of the metals as well, which allows us to recover even more metal. Our bottom ash is extremely suitable as a secondary building material.

Results

Less CO2 emissions

The production of aluminium, for example, emits an enormous amount of CO2. When aluminium is recycled, no more than a fraction of that CO2 is emitted. Which is why it is so important to recover as many metals as possible from waste.

100% recycling

We try to come up with a new application for each fraction that is left over after the incineration process. We are not there yet, but ultimately we want to bring 100% back into the cycle.

Preventing depletion

Bottom ash is a fantastic secondary building material that can help further reduce the use of primary raw materials. For one thing, it can be used very effectively as a sand and gravel substitute.

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Factsheet Bottom ash Download