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What? Municipal solid waste incineration bottom ash (MSWI BA) is the material that is left on the grate after the incineration of municipal solid waste. This material consists of, for example, glass, metals, ceramics, stone, brick, concrete, ash, and melting products, and it resembles natural sand and gravel. About 20-30% of the incinerated waste converts into bottom ash. The annual amount of bottom ash produced in Finland is about 300,000 tonnes, i.e. about 7,500 truckloads.
Why? The amount of bottom ash has increased as the incineration of municipal waste has become more common. In order to prevent the increasing amounts of bottom ash from ending up at landfill sites, it is important to efficiently treat and utilize this material. The treatment also enables the recycling of valuable raw materials in bottom ash.
How? For a long time, bottom ashes have only been coarsely treated for metal removal. Then the leftover has been used, for example, in landfill site structures, even though the material has more valuable utilisation possibilities as well. Minerals from the bottom ash, i.e. our Scanwas manufactured aggregate, can be used to replace natural sand and gravel, for example, in road construction and concrete products. In addition, with our technology, valuable metals can be more efficiently separated and recycled as raw materials for the metal industry.
We are the first company in the Nordic countries to treat MSWI bottom ash with the breakthrough Advanced Dry Recovery (ADR) separation technology. This method has been developed and patented at Delft University of Technology (TU Delft) in the Netherlands and launched on the market by a Dutch company Inashco B.V..
Compared to conventional dry separation technologies, the advantage of the ADR technology is in its ability to recover valuable metals more efficiently. This method does not require bottom ash aging; only the largest metal pieces must be screened. In addition, no waste water is generated, since no fluids are used in the treatment.
We treat annually approximately 100,000 tonnes of bottom ash with our ADR installation. Since 2013, we have treated significant amounts of bottom ashes on our customers' locations in Finland and Sweden.
MSWI bottom ash contains substantial amounts of valuable metals. The ADR dry separation technology separates the sticky and moist mineral fraction surrounding the coarser bottom ash particles. This ensures that also the smallest particles of metals can be recovered. For example, non-ferrous metals, such as aluminium, copper, and lead, account for approximately 4-6% of the treated bottom ash, and the percentage of ferrous metals is about 10%. The ADR dry separation technology enables the recovery of valuable metals instead of dumping them into landfill sites.
Approximately 85% of the bottom ash is minerals that have similar grain size distribution and technical properties to those of natural sand and gravel. The ADR dry separation technology separates metals with such high efficiency that the minerals, i.e. our Scanwas manufactured aggregate, can be used to replace natural raw materials in, for example, road construction and concrete products. In such way, the conventional landfill disposal can be avoided.