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By Neville Passmore

Modern ways of converting wasted organics into soil fertility improvers.

The Mindarie Regional Council serves 7, mostly north of the river councils by taking their domestic waste. In a state of the art facility in Neerabup, they create a composted product that can be used to improve soil in agriculture, pastures, horticulture, forestry, land rehabilitation and landscaped gardens. This is known as OSC and stands for Organic Soil Conditioner.

Green wheely bin waste is collected from cities of Joondalup, Wanneroo, Perth, Stirling and Vincent as well as towns of Victoria Park and Cambridge involving 590,000 residences. The Mindarie Regional Council is Western Australia's largest Waste Management Authority, managing the disposal of over 250,000 tonnes of waste each year. The organic fraction of this waste consists of food, green garden wastes including lawn clippings, paper and cardboard packaging and street verge tree collections.

The Neerabup Resource Recovery Facility uses large rotating steel pipes and automatic compost turners as well as a raft of extraction methods to produce a fine textured, semi-mature compost. This rich material has been extensively used to improve soil fertility around the state. It conforms to the Australian standard number 4454 for compost and mulch

The facility converts 100,000 tonnes of household waste each year into a market quality soil enhancer and reduces the amount of waste currently sent to landfill.

Where has this composted material been used?

Building the Bunbury-Forrest Highway a 37 kilometre link between the Kwinana Freeway and the Old Coast Road was a massive undertaking by the Main Roads Department of WA. At the time of its opening it was the largest road infrastructure project in Australia.

Extensive clearing had to take place and the demand for soil improver and mulch to reestablish the green roadside landscape was little short of monumental. C-Wise and the Main Roads Department won an environmental award for the clever biological solutions that were used on this project. The cleared bush was chipped and mixed with the Mindarie compost as a starter culture. Using windrows, the organic material was composted to the point where pasteurising removed the risk of weed seed and plant pathogen infestation. The resulting composted product was used to improve the fertility of the soil used for planting an extensive range of native plants.

Rehabilitating the Anstey wetlands was a smaller project within this road development. This involved creating an engineered solution to the issue of storm water runnoff from the roadside areas. Slowing the flow of water allowed the reeds and shrubs time to take out excess nutrients and hydrocarbons and prevented these pollutants from entering the nearby Serpentine River.

Moondah Brook winery in Gingin produces premium grapes for the Houghton Wine label. Deep sand makes growing high quality grapes a challenge. One major problem occurs when the vineyard experiences a heatwave that lasts a number of consecutive days. When this occurs before harvest it can have a catastrophic effect. Not only do the leaves wither and turn brown, these can then fall off leaving the grapes exposed to direct sunlight. This results in the berries being sunburned and ripening at different times. This has a devastating effect on the quality as well as the quantity of the harvest. The vines need a moisture retaining mulch that can keep the roots cool and moist over the extended period of heat and drying. While OSC consists of fine particles, once it has been wet, a beneficial fungus binds the material together making a crust that resists wind breakup. While the nutrients and increased biology make bankable improvements in the crop the best outcome is the protection of the bunches from heat stress.

Regan's Ford Estate planted their 87,000 olive trees using OSC as a mulch to hold onto the moisture that is delivered by a micropulse irrigation system. The system aims to apply water to the top 40 to 50mm of topsoil. With soil surface temperatures of 70 degrees Celcius in summer the obvious challenge was to save moisture loss through evaporation and to keep the roots cool so these could continue to do their work. The sandy soil had very limited ability to take up and hold fertiliser for the trees. The mulch layer improved this cation exchange as horticulturists call it and the result was reduced fertiliser costs. As a result of better water storage in the mulched soils, pumping electricity costs were also cut. The saving in water against their allocations has opened up a new opportunity for the farm to intercrop with blueberries.

A sister product from SITA's Raymond Terrace facility north of Newcastle in NSW produced from exactly the same types of urban waste has been used to progressively revegetate the Ashton Coal mine in the Hunter Valley. Here the compost is incorporated with the saved topsoil when mining is completed. This mix is then applied over the fill and then plants and seed are used to revegetate the area. This has proved so successful that over 100,000 cubic metres is delivered to the mine every year.

What can we do as householder to help in this recycling effort? The most difficult thing to eliminate from the recycling process is glass. If homeowners can divert all glass to the recycle bin it would make a profound difference to the usability of the composted products and reduce the risks of handling for gardeners and farmers.



Rubbish loaded into composting process


Maturation shed with automated windrow turner



Finely textured final product is ready for shipping out