Secondary construction materials: Nature comes first

The use of secondary aggregates such as recycled aggregates from construction and demolition waste, industrial by-products or waste incineration bottom ash/slag is subject the corresponding environmental regulations. When reusing such secondary building materials, the protection of groundwater and soil have priority – as stipulated in the Water Resources Act (WHG), the Federal Soil Protection Act (BBodSchG) and the Federal Soil Protection Directive (BBodSchV).

Main environmental rules

On 1 August 2023, the Secondary Aggregates Directive (EBV) will come into force as part of the Mantelverordnung. Until then, the regulations of each federal state are currently decisive regarding environmental applicability of incinerator bottom ash in road construction and earthworks. Many federal states work on the basis of Notice M 20 of the Working Group of the Federal States on Waste (LAGA M20). Some federal states developed own regulations, for example North Rhine-Westfalia has created a number of decrees on this subject as a legal basis.

Incinerator bottom ash (IBA) is recycled in accordance with environmental regulations

Further information pertaining to environmental regulations is given in our Handbook on secondary aggregates Order free of charge

Differentiation of applicability based on local conditions

Both LAGA M20 and the NRW decrees define the recycling areas on the basis of their importance for groundwater and soil protection. When determining the possible areas of application, a distinction is made between utilisation inside and outside of water protection areas, flood plains and hydrogeologically sensitive areas. The use within the aforementioned areas always requires a more in-depth investigation of the geological and hydrogeological conditions on site. This means increased effort and can lead to uncertainties with regard to the possible applications for many of those involved in the construction.

Recovery of IBA in water protection zones I and II is not permitted

The use in water protection zones of categories I and II is not permitted.

Application of incinerator bottom ash: Use restricted in WSG IIIA/HSG III and WSG IIIB/HSG IV

The use within the water protection zones WSG IIIA/HSG III and WSG IIIB/HSG IV is restricted according to both LAGA M20 and the NRW decrees. Decisions on application should be made on a case-by-case basis.

Use of IBA in Germany allowed outside of water protection zones

The use outside of water protection areas, flood plains and hydrogeologically sensitive areas is generally permitted.

Conclusion and recommendation

In accordance with ecological and technical regulation, it is advised that incinerator bottom ash (IBA) from Energy-from-Waste plants is only used outside of water protection areas, flood plains and hydrogeologically sensitive areas. Also, the following conditions apply:

  • A minimum distance of at least 1 m between the base of the material and the highest expected groundwater level must be adhered to.
  • The minimum distance to corrosion-prone buildings equals at least 0.5 m.
  • In the case of private construction projects, a building permit pertaining to water law must be obtained prior to the start of construction based on municipal requirements.
  • The construction has to be carried out under watertight surface layers such as concrete, asphalt or bitumen spraying.