HVC and Boskalis Environmental build unique washing plant for incinerator bottom ash

From left to right: Haico Wevers, Mayor Bruinooge and Dion van Steensel.

HVC and Boskalis Environmental are the first in the world to build a large-scale, fully integrated washing plant for incinerator bottom ash. The unique feature of this system is that it washes and works up the bottom ash from a waste-to-energy plant, and the result can then be used as freely applicable building material. Mayor Bruinooge officially launched the construction work for the plant at the site of the HVC waste-to-energy plant in Alkmaar today. The plant is expected to go operational in the summer of 2016.

Bottom ash is the residual product of waste incineration in a waste-to-energy (W2E) plant. HVC currently processes bottom ash in its slag upgrade facility. In this traditional processing method, the W2E plants have to ensure that contaminants remaining in the bottom ash cannot be leached out by rainwater. At the moment, one approach to doing this involves enclosing the material in sheeting. The new washing plant flushes harmful substances out as the bottom ash is being washed. The remaining material can therefor be 'freely applied' - without isolation measures or further processing - in, for example, road-building as a substitute for sand, but also in concrete and asphalt. 'The washing and working up of the ash is an excellent example of the circular economy. The complex regulations for using bottom ash will become a thing of the past. Bottom ash will, for the first time, be a fully-fledged alternative for sand,' explains Dion van Steensel, the HVC director.

The new washing plant will also have the technology to recover other types of valuable non-ferrous metals (copper, gold, lead and aluminum) from the bottom ash. In the current process, HVC recovers approximately 1.5% of non-ferrous scrap from the bottom ash. The new process boosts that figure. Research shows that residual waste in the Netherlands contains gold with a value of €27 million. 'Another benefit is that precious metals are recovered from the sand fraction. This generates not only additional revenue but also significant environmental benefits because all these recycled metals no longer need to be extracted from primary ores,' explains an enthusiastic Haico Wevers, the director of Boskalis Environmental.

The plant will allow HVC to comply with the schedule for fulfilling the environmental agreements made in 2012 between the government and the W2E sector. That Green Deal stipulated that half of all processed bottom ash has to be freely applicable by 2017, and all bottom ash by 2020. In addition, it sets out a minimum for the recovery of metals and requires less than 15% of residual material to be left over. In the new plant, all the bottom ash from HVC will be transformed into a freely applicable building material, more metal will be recovered than before and less than 15% residual material will remain. This means that HVC is more than fulfilling the agreements with the Ministry of Infrastructure and the Environment.