What is quality compost?

One of the most frequently asked questions is also one of the more complex to answer – what is quality compost?

It can be confusing to be presented with a range of manures, composted manures, raw mulches, quality composts and mulches and other organic materials – how do you decide which is best for you? The answer to this question will depend on how the material is to be used. The ideal properties of mulch for roadside landscaping will be very different to those required for top dressing turf.

In general, quality compost should comply with the Australian Standard for Soil Conditioners and Mulches (AS4454). Always remember that quality is not just about how a compost looks or how much it costs. Look for compost products that are supplied with clear product information, including information on how they should be applied in your particular situation. The Compost Australia Leaf Mark certified composts (based on AS4454) are designed for specific applications and are supplied with standard product information sheets.

Compliance with other certification schemes, such as organic certifications (BFA and NASAA), demonstrates the processors commitment to maintaining and improving product quality. Quality composts have undergone quality controlled processing – your compost processor will be willing to take you on a tour of their composting site to show you the process, monitoring and testing that is undertaken. Please contact one of our industry development officers for assistance with interpreting the results of compost analyses.

Poorly or non-composted materials pose the risk of introducing pests and pathogens, weed seeds and may behave less predictably than material which has undergone the stabilising phase of the composting process. Non-composted manures may conceal a surprising amount of salt, contributing significant amounts to the soil with prolonged use.


Key characteristics of quality compost:

  • high levels of organic matter and nutrients

    Organic matter is vital for good soil health and adding quality compost with organic carbon to the soil helps to improve soil condition. Australian soils are generally low in organic carbon – one of the key indicators of soil fertility. Increasing organic matter (and organic carbon) by using quality compost improves soil fertility and promotes healthy plant growth. Compost also provides the soil with a range of important nutrients that are essential for plant growth.

  • free from weeds and diseases

    Weeds and diseases are the last thing you want to introduce into your environment and adding quality compost will ensure that your landscape is not at risk. Quality compost has been through a full composting process which involves pasteurisation and microbial transformation for at least 6 weeks. During this professionally managed composting process, temperatures are high enough to disable even the toughest weed seeds. As well as being free of weeds and diseases, quality compost will have a pleasant smell.

  • it has been professionally composted and complies with the Australian Standards

    Quality compost will be produced by quality processors! The best place to look for quality compost is at compost companies that are members of Compost WA and are committed to improving industry standards and customer satisfaction. Quality processors will be happy to supply you with information and advice about using compost as well as welcoming a tour of their facilities so you can see first hand where quality compost is made.

Benefits of using Recycled Organics


Recycled organic products are made from garden organic material collected from a range of sources including household green waste bins and commercial landscaping operations. Recycling these waste products means that a large chunk of material is diverted from landfill. In Western Australia alone, 178,563 tonnes of garden organic material was diverted from the waste stream in 2008 and recycled1.
1 Recycled Organics Unit (2008). Organics Recycling in Australia: Industry Statistics 2008. Report prepared for Compost Australia by the Recycled Organics Unit. Internet publication www.compostaustralia.com

Water efficiency:

The water efficiency of your next landscaping project will be improved by the application of any RO product. Using compost mulch will help to prevent water from evaporating out of your soil, while the application of compost and soil conditioners will improve the structure of your soil and increase its water holding capacity.

Compost mulch also insulates the soil against fluctuating temperatures and as a result plants root systems are less stressed by changing conditions and are more drought tolerant.

Sustainable landscape benefits:

Aside from diverting waste from landfill, using RO products can be a great substitute for some less sustainable landscaping practices. Organic soil or soils blended with compost soil conditioners can be used as replacement soil in landscaping situations where no topsoil is available or it is of very poor quality.

Using RO products to replace topsoil reduces the need for harvesting of natural soils from river beds, flood plains or other environmentally sensitive areas. Using RO also returns organic carbon to the soil where it can be stored – this is vital for combating the challenges of climate change.

Compost mulch may also be a more sustainable option than using wood chips or other by-products of the forestry industry. Using RO products as a component of potting mixes is also more sustainable than using peat which is mined from sensitive peat bogs and wetland areas.

Low maintenance landscaping

  • Recycled organic (RO) products like compost mulch can do a lot of the landscape maintenance work for you.
  • Compost mulch can reduce the need and/or frequency of irrigation which can save significant time and money, particularly if manual watering of landscaped areas is needed.
  • Weed and disease control is another important feature of RO products. Compost mulch can prevent weed growth, reducing the amount of herbicide (and labour) needed to maintain landscaped areas. RO products also naturally contain bacteria that can help fight off plant diseases.
  • RO products improve soil structure and nutrition over time, meaning that less fertiliser may be needed to maintain healthy plant growth. These benefits can continue over several years and as a result, save considerable amounts of money.
  • Compost mulch can last longer in your landscape than raw mulch which in some cases may need to be replaced each year.

Where can I find Quality Compost?

Good suppliers can produce a product that specifically suits your needs and be able to produce it consistently. Your supplier should also be able to supply you with a current analysis of the compost, material safety data sheets (MSDS) as well as indicating the best way to apply and use their products. Quality processors will encourage you to tour their facilities and see how their compost is processed.

Find your nearest producer of quality compost via our Supplier Directory.

Compost and Climate Change

The Federal Government describes the Carbon Farming Initiative as a scheme to help Australian land managers, forest growers, and farmers to earn income from reducing emissions or storing carbon in the landscape.

But what is the Carbon Farming Initiative? How does it work? How do land managers earn carbon credits and what land-based activities are considered eligible?

And where does Compost fit into the CFI puzzle? It is well documented that preventing organic residues from going to landfill avoids methane emissions and also preserves organic carbon and nutrients for beneficial use in land management and food production. It is equally well known that on-going use of compost improves physical, chemical and biological soil properties.

The agricultural and horticultural use of compost also supports climate change mitigation on two fronts:

  1. Removal of atmospheric carbon through soil carbon sequestration achieved directly through storage of compost carbon, and indirectly through enhanced plant growth, which in turn contributes also to increased soil carbon levels.
  2. Reduction of greenhouse gas (GHG) emissions through reduced use of chemical fertilisers and pesticides (and thus production of these products) and through reduced irrigation.

Carbon Farming Initiative Project

NSW Carbon in Compost Project

The Carbon Farming Initiative (CFI) project funded by NSW EPA and individual processors in NSW was designed to explore the amount of long term (recalcitrant) carbon in compost products and to find an inexpensive way to model carbon for carbon trading purposes.

The project sought to answer the question: Do measures of biological stability of compost correlate with carbon characteristics? Of particular relevance is whether biological stability measures could be used as indicators of recalcitrant carbon.

The first stage involved sampling and testing of a range of different composts over a 12 week period, testing biological stability and other important parameters at different maturities. Products tested included green waste, food and green, biosolids, msw, and humified composts.

Stage two planned to involve these samples being tested by the CSIRO for recalcitrant carbon. These results will determine if such a postulated correlation is quantifiable with an appropriate level of confidence. Completion of this initial work has been delayed, as CSIRO were unable to analyse samples at the time due to an overload of samples in their system, technical difficulties and mechanical failure.

CSIRO Project: Increasing Soil Carbon with Organic Amendments

In the interim CSIRO has successfully secured new funding to broaden the project.

The project will investigate how organic amendments differ chemically, how this relates to their stability in soil, and how soil type affects this stability. The data generated in this research will also be used to investigate the suitability of rapid spectral (MIR/NIR) techniques for estimating organic amendment stability, and to refine how models handle organic amendments.

This information will inform the land sector and policy makers as to the suitability of differing organic amendments for Carbon sequestration. The results of this analysis will be used within FullCAM (the model used to construct Australia’s national greenhouse gas emissions account for the land sector) to provide consistency with Australia’s national inventory and CFI methodologies.

While the outcomes of this research are some time off (2015), the findings may lead to the development of CFI methodologies for landholders applying composts and organic amendments to receive carbon credits via carbon offset schemes.

CSIRO Needs More Samples
While the initial project is still to be finalised, another 30 samples are required by CSIRO to be included in the project.

Clarification of the compost samples to be included in the broader project is yet to be determined. Preference will be given to compost samples that:
• Cover organic inputs not already tested, and
• Are processed in commercial volumes under verifiable process controls.
All sampling procedure, storage and forwarding instructions will be carried out by the AORA NSW MIDO.

This is an opportunity for you learn about the carbon sequestration potential of your products. If you are interested in having your compost or other organic amendment sampled, please contact Darren to arrange for sampling and testing.

Your individual test results will be shared with you confidentially. All final results however, will be aggregated and will not identifiable by business.

Contact your us via email: admin@aora.org.au