Contamination Free Mulch

Mulch refers to any type of material that is used as a soil covering that can be spread or laid. It is used to assist moisture retention in gardens, to improve the fertility and health of soils, acts to regulate soil temperatures and can suppress weed growth. Mulch can also be used for aesthetic purposes in public open spaces to enhance the visual appeal of an area and to provide soft-fall surfaces at playgrounds.

Mulches derived from organic material are the most common type of mulch, although plastic sheeting and shredded rubber from recycled tyres can also be used as mulch. Organic mulches may be comprised of:

  • Shredded or chipped bark and wood
  • Chipped, uncontaminated, recycled wood products
  • Compost and composted manure
  • Grass clippings
  • Newspaper
  • Straw

In Australia, the minimum quality standards for mulch, compost and soil conditioner products are described by the Australian Standard AS4454 - 2012: Composts, Soil Conditioners and Mulches. This standard applies to all manufacturers and suppliers of these products in all market sectors; including supply of mulches for domestic use, urban landscaping, agriculture and land rehabilitation. WA Health supports the adoption of this standard for manufacturers and suppliers of mulch in Western Australia as it provides guidance on minimum acceptable concentrations of potential chemical contaminants.

Asbestos

The Australian Standard AS4454 does not provide guidelines for asbestos in composts, soil conditioners or mulch. Only New South Wales has requirements specifically relating to asbestos in mulch. The Mulch Order 2016 states that any processor who supplies mulch must ensure that "the mulch does not contain asbestos". Main Roads Western Australia also requires that mulch is free of fine or fibrous particles (Specification 304: Revegetation and Landscaping). Consistent with these, WA Health recommends that all mulch products be visibly free of asbestos and asbestos-containing materials at the point of sale or supply. WA Health does not propose a guideline value as there are currently no published methods for the determination of asbestos in mulch. Where any visible contamination is found, the material is no longer considered suitable for sale or supply as a mulch product.

To ensure that mulch is contaminant-free for all potential uses, including commercial and private environments, it is important for all mulch producers and suppliers to undertake appropriate visual screening of all raw materials and remove products such as treated wood, asbestos-containing materials, plastics and glass from the feedstock. Suppliers should also be aware that the sale of mulch containing visible asbestos can be prosecuted under Regulation 6 of the Health (Asbestos) Regulations 1992.

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