Compost and farm biosecurity

Effective farm biosecurity relies on being aware of the risks of anything that comes on to the farm.

When using organic soil amendments, such as composts or soil conditioners, producers must be confident that products brought on farm don't pose a risk to the farm business or consumers.

The benefits of compost

Compost is the result of the natural decomposition process that occurs with all organic material in the presence of oxygen.

Composting reduces the amount of waste going to landfill and is a valuable source of organic matter for soils which contains nutrients for plant growth.

Commercial compost producers are simply speeding up the natural process of decomposition by optimising and controlling an otherwise natural process. By creating the right environment, the decomposition process of any organic material can not only be accelerated, but also manipulated, to produce the desired results.

Farm biosecurity

All farms should have a biosecurity plan that includes measures designed to protect the property from the entry and spread of pests, diseases and weeds.

Compost products need careful consideration and all risks should be evaluated prior to bringing onto the farm. In addition to the careful selection of all products going into a farming system, farmers need to take precautions during compost storage, application and subsequent grazing or cropping activities on farm.

Product selection – potential risks

One of the first questions to ask when selecting a suitable compost is:

Where is the material from and is there a chance it could contain 'restricted animal material' (RAM) or 'prohibited pig feed' (swill)?

RAM includes any material taken from a vertebrate animal other than tallow, gelatin, milk products or oils. It includes rendered products, such as blood meal, meat meal, meat and bone meal, fish meal, poultry meal and feather meal, eggs, and compounded feeds made from these products (Animal Health Australia, 2019).

Any compost produced using any parts of animals, or animal derived products (including animal carcasses, poultry litter, pig manure, grease-trap waste, abattoir waste or food wastes) may contain RAM.

Under current legislation in all Australian states and territories, it is illegal to feed RAM to ruminant animals or to allow ruminants (cattle, sheep, goat, buffalo and deer) access to a stockpile of material containing RAM.

This restriction is referred to as the ruminant feed ban. It was introduced in 1996 to minimise the risk of spreading the bovine spongiform encephalopathy (BSE) agent, commonly known as 'mad cow disease'.

Swill refers to any mammalian product (including imported non-stockfeed dairy products), or material that has been in contact with any mammalian product (excluding dairy and mammalian products rendered to the Australian standard).

Under current legislation in all Australian states and territories it is prohibited to feed swill to pigs or to allow pigs to access a stockpile of material containing swill.

Guidelines for managing products that may contain RAM or swill, or pose a pest and disease risk, include:

• Designate areas for compost delivery and storage. The sites should have a hard, clean base, be easy to access by machinery year-round, and must be inaccessible by stock.
• Careful consideration should be taken when storing compost to prevent contamination through run-off, odour, groundwater reserves and movement of windborne particles/dust. Use of plastic as a base or to cover the compost pile is not recommended due to its degradation over time. Refer to the EPA Guidance Designing, constructing and operating composting facilities (EPA publication 1588.1).
• Where compost containing RAM is spread on a pasture paddock used for grazing ruminant animals, the livestock should be kept out of the paddock until there has been sufficient pasture growth to absorb the compost, to limit any ingestion of potentially contaminated soil by animals. Access should be restricted until 1) a 21-day period has elapsed since application and 2) regrowth has occurred and 3) a minimum grass height of 4cm can be sustained at all times (even after grazing). Piles of the material must not remain.
• For cropping applications, compost is best applied just before sowing. It can be left on the soil surface as a mulch or can be incorporated into the soil. Consult an agronomist for further information.
• Pig producers in particular need to be aware of the swill and prohibited pig feed ban. Any product with mammalian meat, meat products or any food that has come into contact with meat is prohibited feed, and must not be fed or supplied to pigs, or stored on a pig property.
• Minimise the chance of vehicles introducing pests, weeds and diseases by ensuring that contractors delivering or spreading anything implement effective wash-down practices when moving between properties.
• Always wear gloves, respirator or dust mask and eye protection when handling compost and wash hands and clothing afterwards. Make sure all staff are aware of biosecurity risks.

Other product risks to be aware of

Commercially made composts can be sourced from a broad range of waste products. These can include:

• green wastes
• mixed kerbside organics recycling bins (garden waste/food waste, including meat scraps)
• food processing wastes
• abattoir wastes and animal fats
• Biosolids from sewerage treatment plants.

Potential risks to be aware of when using these compost products include;

• heavy metal contamination
• herbicide residues
• high levels of soluble salts
• per- and poly-fluoroalkylated substances (PFAS)
• high carbon to nitrogen ratio levels
• physical contamination such as plastic, glass, metal, rocks and twine.

Potential pathogens of concern in composts derived from animal excreta or offal, unsegregated municipal solid waste, sewage sludge or other wastes with a high pathogen risk should be identified and appropriate surrogates tested to ensure that they are not present at levels posing a biosecurity risk.

Pasteurisation and maturation of compost

The composting process is separated into two phases:

• pasteurisation
• maturation

When sourcing a high-quality compost, consider what product you (and your customers) require and look for documented evidence that it meets the required standards. It is legal to sell immature compost, which must be pasteurised and have pathogen levels below parameters in EPA publication 1588.1 (Table 8), but until compost is mature it can have odour and be biologically active, with some detrimental effects on plants and soil.

An effective pasteurisation phase is essential to significantly reduce the number of human, plant and animal pathogens, and viable regenerative plant materials or seeds.

Due to the potential presence of RAM or swill in kerbside recycling bins, abattoir waste and grease-trap waste, effective pasteurisation of organic compost is required to reduce the risk of exotic animal diseases, such as foot and mouth disease, or African swine fever (ASF), which could be transmitted to livestock via illegally imported meat products.

The ASF virus can survive for up to 300 days, including in some ham products.

It is important to note that an effective pasteurisation phase may not kill all pathogens, including:

• some resilient viruses such as bovine and porcine parvoviruses
• the bacterial spores that cause animal diseases such as anthrax, blackleg, tetanus, botulism, Q fever and Clostridium difficile infection
• some more resistant bacteria such as Mycobacterium avium paratuberculosis, the Johne's disease agent
• some livestock nematode eggs such as Ascaris sp.
• prions - the infectious agents responsible for BSE.

Maturation is the second stage of the composting process where the microbial activity slows and the compost begins to stabilise to an extent that it can be safely used on land and to come into direct contact with plants without any negative effects (EPA, 2017).

There are a variety of methods to demonstrate the level of maturity of a compost product. These include reporting the details of the processing conditions and a variety of laboratory tests that can be undertaken by National Association of Testing Authorities (NATA)-accredited laboratories.

Quality assurance programs for compost

The Australian Standard for composts, soil conditioners and mulches (AS4454-2012) is the industry standard for determining compost quality.

Producers are strongly advised to check that composts used in agriculture have been independently certified as meeting the Australian Standard.

AS4454 describes three products: pasteurised, compost and mature. Management of high-risk feedstocks such as food and abattoir waste requires referring to the EPA Guidelines (EPA publication 1588.1). Composting as per AS 4454 is not appropriate for livestock carcasses (dead animals) on farm.

There are also organic certification schemes such as NASAA (National Association for Sustainable Agriculture Australia Limited).

Other certification schemes such as the Compost Australia Leaf Mark certified composts (based on AS4454) are designed for specific applications and compost under this scheme is supplied with standard product information sheets.

As well as a product that contains the Australian Standard certification tick, look for compost suppliers that can supply you with a current analysis of the compost and material safety data sheets (MSDs), as well as guidance on the best way to apply and use their products.

Quality processors will encourage you to tour their facilities and see how their compost is made, and should be able to provide a certificate of compliance detailing test results and feedstock origin.

The application of waste to land is prohibited and carefully controlled by EPA Victoria.

Farms looking to apply organic waste derived compost or soil conditioners to their land must ensure that the organic material to be applied is a compost or soil conditioner product and no longer a waste.

Compost and soil conditioners that only meet the pasteurised product standards of AS4454 are still considered a product by EPA Victoria however there may still be restrictions on their use for biosecurity and environmental protection.

Check the processor's guidance on the best way to apply and use their products, including any withholding periods.

Record keeping and reporting

Keep records of when compost or manures were spread was spread, where it came from, how much was used and any other specific information about the product.

Record-keeping and monitoring of paddocks is important for traceability in the event of any biosecurity issues such as pest incursion, disease outbreak or contaminants in products produced.

Keep a close eye on paddocks that have compost spread on them for signs of anything unusual. New weeds, pests or diseases need to be identified quickly, contained and eradicated to prevent spread.

If any new or unusual pest or disease occurs, inform your local agronomist or veterinarian.

Alternatively call the Emergency Animal Disease Watch Hotline (1800 675 888) or the Exotic Plant Pest Hotline (1800 084 881) without delay.

For more information

For more information on managing composts on farms in Victoria phone the Customer Service Centre on 136 186, or refer to:

• Dairy Australia – Composting (see further fact sheets under Resources)
• Grains Research and Development Corporation (GRDC) Fact Sheet – Recycled Organic Fertilisers

References

Animal Health Australia (2019). Australian Ruminant Feed Ban.

AS 4454: 2012 – Australian Standard 4454:2012 for Composts, Soil Conditioners, and Mulches. Australian Standards, Sydney, Australia.

EPA Victoria 2017. Guideline for designing, constructing and operating composting facilities. Publication 1588.1* June 2017. Melbourne Victoria. EPA publication 1588.1

Agriculture Victoria (2022) On-farm Composting of Dairy Cattle Mortalities Fact Sheet Victorian Government, Melbourne.