This presentation was held at the thematic event on recycling technologies in landfill management projects held in Mechelen on July 3, 2019.
Marian Langevoort (Tauw) presented the transformation of Municipal Solid Waste Incinerator (MSWI) Bottom Ash into a freely applicable building material- EquiAsh.
In the Netherlands, for more than 25 years, all bottom ash produced is applied as building material with ICM-measures (Isolate, Control, Monitor). However, policy wish is to ban ICM constructions.
MSWIs decided to improve the quality of the bottom ash such that the criteria for freely applicable building material are fulfilled. These agreements are done in the framework of the Green Deal: transition of bottom ash to a freely applicable building material (50 % in 2017, 100 % in 2020). Different studies have been undertaken in order to avoid leaching of heavy metals, the acidity degree (pH) seems to be an important parameter. As a result Tauw has developed the EquiAsh process, a three steps process that allows the ashes to be used as freely applicable building materials. In the carbonation phase CO2 enriched air flows over the raw ashes leading to a drop in pH resulting in fixation of metals (Cu, Pb, Al, Ba, Mo). In a second step soluble components and salts are washed in a slow washing process. The final mineralisation step ensures further fixation of metals. This process results in a processed bottom ash that can be used a freely applicable building material.