Development of bottom ash washing facility

A test facility for washing bottom ashes is rising up at our Boeldershoek site. With this temporary facility we aim to acquire knowledge about the development of a permanent bottom ash washing facility, to be constructed in 2021. In addition, we would like to produce a washed product now that can be used as a freely applicable construction material.

Foto opbouw testinstallatie bodemassen

By expanding our bottom ash reprocessing facilities with a washing facility it will become possible to produce sustainable, freely applicable construction materials from bottom ashes, on a large scale. Washing the bottom ashes removes any remaining leachable metals and salts. Because the quality of the end-product in part depends on the composition of the bottom ashes, adjustments are also being made to the energy from waste plant that forms part of the existing bottom ash reprocessing plant constructed in 2014.

We are devoting a great deal of attention to treating the wastewater released by the future washing facility. We would like to find partners with whom we can develop the best possible technology that would enable us to deliver clean bottom ashes with clean water as the only by-product. This is why we are using a so-called innovative partnership tendering process. This form of tendering is new for Twence and is furthermore unique within the sector. We are guided in this process by experts from Twijnstra-Gudde.

According to current plans, we will be able to supply a clean and freely applicable construction product from our own plants, starting in 2022.

Green Deal
Bottom ashes are by far the largest stream of residual materials from energy from waste plants. Up until 2012, bottom ashes were only permitted to be incorporated into, for example, roads, inclines and noise barriers, in accordance with the strict Isolate, Control and Monitor (ICM) rules. Protective measures designed to avoid contamination of the substrate by preventing the metals and salts still present in the bottom ash from flushing out, had to be implemented.

In 2012, in a Green Deal with government, the energy-from-waste sector agreed that bottom ashes had to be fully freely applicable in the future – and therefore had to be free from leachable materials. This makes them an excellent replacement for sand or gravel in the road construction sector, for example. Alternatively, bottom ashes must be of such quality that they can be used in ‘structured construction materials’, such as concrete slabs and kerbs. In this form, any remaining metal fractions are fixated and stabilised.
The washing facility that we are developing and will be constructing on our own site will ensure that our bottom ashes comply with the requirements set out in the Green Deal.