Fly ash can be generated by a number of different incineration processes. The content of the ash varies, which means that the treatment method must also vary.
For many years, fly ash from coal-fired power stations has been used as aggregate in the concrete industry. Up to 30 per cent of concrete can be fly ash. The predictable quality of fly ash from power stations is due to the fact that the furnaces receive the same type of fuel.
However, fly ash generated by the incineration of waste cannot be used in concrete. The content of the ash varies according to the waste which has been incinerated. This would result in quality variations which would be unacceptable to the concrete manufacturers.
The ash which is used in NOAH’s treatment plant contains around two per cent heavy metals; the remainder is carbon and salts. This proportion of heavy metals is enough to classify the ash as hazardous, inorganic waste.