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Environment Protection Authority

Environmental Issues

Waste and recycling

Organics processing technologies

Turned windrow

Mechanical turning of an organics windrow

Mechanical turning of an organics windrow

A system of composting involving the aeration of horizontally extended piles formed by a front-end loader or windrow turner.

Extended piles are generally 1.5 to 3 m in height, and length is limited by the size of the composting pad. Aeration is achieved by mechanical turning.

Aerated static pile

A method of composting in which a free standing pile is aerated by a blower moving air through perforated pipes located beneath the pile.

In-vessel

A system of composting involving the use of an enclosed chamber or vessel in which (in most cases) the composting process is controlled by regulating the rate of mechanical aeration.

Aeration assists in heat removal, temperature control and oxygenation of the mass. Aeration is provided to the chamber by a blower fan which can work in a positive (blowing) and/or negative (sucking) mode. Rate of aeration can be controlled with temperature, oxygen or carbon dioxide feedback signals.

Anaerobic digestion

An organic treatment system involving the microbial decomposition of organic materials in a solid, semi-solid or liquid phase in the absence of oxygen, converting part of the organic fraction to carbon dioxide and methane.

Systems may take the form of covered lagoons, covered stabilisation basins, or completely enclosed agitated or non-agitated towers.

Methane recovered needs to be purified to remove carbon dioxide (in most cases) if used as a combustive energy source.

Anaerobic digestion mostly occurs at mesophilic temperatures, though methane recovered by some systems is used to heat the reaction chamber to thermophilic temperatures to speed up the digestion process.

Vermiculture

A system of stabilising organic materials under controlled conditions by specific worm species and microorganisms under mesophilic temperatures.

Commercial vermiculture systems include:

  • windrows or beds
  • stackable trays
  • batch-flow containers
  • continuous flow containers.

Other alternative waste treatment (AWT) technologies

The systems described above relate mainly to the processing of source-separated organic materials.

Facilities also exist in NSW which accept mixed solid waste from municipal and commercial/industrial collections.

These facilities seek to remove non-compostable materials and recyclables from the waste stream before processing the remaining organic fraction. These involve patented technologies of a rotating drum followed by aerated static pile curing and with another facility using a 'percolator' followed by anaerobic digestion for the liquid stream and in vessel composting for the solid stream.

Feedstock selection

Organic materials used for composting or related biological treatment systems vary. Different feedstocks have different nutrient concentrations, moisture, structure and contamination levels (physical, chemical and biological).

It is important to ensure that your feedstock is appropriate for the facility that will be processing the organic materials.

 

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Page last updated: 14 January 2015