Towards Zero Waste: Organic Project Showcase

Current Projects available:

Background

On average 540,000 tonnes per annum of organic resources are diverted from landfill and processed into quality recycled organics products by the composting industry in Western Australia. There is opportunity to divert even more organics by educating market places about the benefits and actual costs associated with the application of recycled organics products.

An assessment into the market potential for recycled organics was commissioned by Department of Environment and Conservation (DEC) in 2007. This assessment identified the Urban Amenity market sector as having the largest potential for immediate growth on the sandy soils of the Swan Costal Plain.

  • Local government
  • Landscape contractors
  • Home gardeners

DEC considered that the most appropriate sub-sector to target from a State government perspective was local government. The uptake of recycled organics products by local government can be slow due to perceived increases in costs and risks associated with changing proven practices. In addition, as regional councils have or are implementing Alternative Waste Treatment (AWT) technologies, there is a need to demonstrate where AWT derived compost can be utilised. Outcomes from a market development workshop for recycled organics held at the 2007 Waste and Recycle Conference indicated that demonstration sites and subsequent communication of cost benefit analysis would assist overcoming these barriers.

DEC in conjunction with Main Roads WA and a major construction company has established demonstration sites along the new Perth to Bunbury Highway to show the benefits of compost as a growing medium and provide accurate costs of its use. Demonstration sites have also been established in conjunction with the City of Perth on the Esplanade (adjacent to the Convention Centre) to assess and show uses for AWT derived compost

The New Perth to Bunbury Highway Project

DEC, in partnership with the Southern Gateway Alliance (SGA) and Compost WA members, is currently investigating the use of recycled organics products in road verge, median strip and wetland construction on and around the new Perth to Bunbury Highway project. The aim of the project is to demonstrate the benefits of compost as a growing medium and provide an accurate analysis of the costs of its use in major road construction and revegetation projects. After an appropriate amount of time where growing rates can be assessed, the methods and costs of applying the recycled organic products, in comparison to conventional methods, will be made available to local government.

There are two components to the project:

  • Road verge and median strip revegetation of three major interchanges at Foley Road, Karnup Road and Pinjarra Road along the new Perth to Bunbury Highway.

                                  

The intent of this component is to demonstrate the use of AWT derived compost and mulch prepared from on-site vegetation for developing improved methods for road verge and median strip revegetation.

The material being used in roadside and median strip vegetation is a mixture of topsoil and shredded organics (removed during road construction) blended with various ratios of AWT derived compost.

Vegetation growth rates, costs of shredding, blending and applying will be presented in a report, with findings communicated through workshops, fact sheets and on the zerowaste website.

  • Construction of a new wetland located adjacent to the Perth / Bunbury Highway adjoining Bush Forever Site 277 to the east of the new road formation.

                                  

The intent of this component of the project is to assess the use of quality; meeting Australian Standard requirements; processed composted soil conditioner in constructing artificial wetlands. The wetland has been designed for flood mitigation purposes and to act as a habitat corridor between two Bush Forever sites bordering areas of the highway construction. The wetland has also been designed to receive stormwater from the road pavement and remove pollutants prior to discharge into the surrounding environment.

Given the low fertility soils available to support the establishment of wetland vegetation, it is envisaged that the composted soil conditioner may be ideally suited to improve the quality of on-site soils.

A variety of treatment plots have been designed across the site, taking into account the two vegetation communities (Heath sp. dominant and Tuart sp. dominant areas) that are planned to be established.

The Tuart area treatment plots have been spread with varying rates (20mm, 30mm and 40mm) of a product that was blended onsite (40:60 compost/mulch blend). Following surface application, the product was rotary hoed into the top 100mm of the existing topsoil.

The Heath area has been spread with two different blends of compost product at varying rates. The blends applied were:

  • 40:60 compost mulch mixture (applied at 40mm thickness)
  • Composted soil conditioner (applied at rates of 20mm, 30mm and 40mm).

All four treatment variations were rotary hoed into top 100mm of the existing topsoil, following surface application.

To enable proper analysis and comparison; both scientific and economic; each treatment area established onsite has an associated control plot where traditional techniques have been employed.

Vegetation growth rates, costs of shredding, blending and applying will be presented in a report, with findings communicated through workshops, fact sheets and on the zerowaste website. In addition, the benefits and costs of using compost will be assessed against the use of artificial fertiliser.

The project is proposed to run for a minimum of two years to enable data to be gathered on the use of recycled organics products over the longer term in comparison to the use of artificial fertiliser. Finally, a risk assessment will be undertaken to ensure that the application of compost does not leach excessive amounts of nutrients into the groundwater, which will extrude to the wetlands.

Turf Replacement Project using a sub-turf application of both Source Separated and AWT derived Compost – The Esplanade, Perth.

                                  

DEC is currently working with the City of Perth to investigate the environmental and economic benefits of using recycled organics (compost-based) products in turf management applications commonly undertaken by local government.

The western end of the Esplanade was selected as the trial location to evaluate the benefits of applying compost derived from source separated as well as AWT as a growth medium under turf. The trial will compare the quality and condition of the Kikuyu turf surface laid over compost in comparison to that laid over yellow sand.

The total trial area is 9600m2 divided into five equal plot areas of 1920m2, and treated as follows:

  • Two treatments with AWT derived compost, at 10mm and at 30mm thickness;
  • Two treatments with source separated green waste derived compost, at 10mm thick and 30mm thickness; and
  • One control plot with no compost applied.

The compost was spread and lightly hoed into the top 100mm of the soil surface. Kikuyu turf was laid over the top of all plots and all plots were subjected to the same watering regime. Baseline soil analysis was conducted and a sampling regime is being conducted over the next twelve months for soil and tissue analysis.

Improvement in turf growth rate, resilience to water restrictions, reduction or potentially elimination for the need of chemical fertilisers, and recovery of turf after heavy usage will be assessed and documented.

The results of the trial will be documented in the form of a case study to help promote and encourage the usage of compost by local governments across Western Australia.

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