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COMPLIANT COMPOST

DOCUMENTING SAFE COMPOST PRODUCTION

WHY COMPLIANT COMPOST?Food safety programs such as Freshcare, SQF and HARPS all restrict the use of untreated manures on crops. The withholding period between application of untreated manures and harvest ranges from 45 to 365 days, depending on the standard. Risk is highest for produce that is grown in or near the soil and can be eaten uncooked. Longer withholding periods apply for these crops.

Compost, however, does not attract such restrictions. It is treated to kill human pathogens, so can be used freely. However, evidence of treatment must be provided. Without this evidence, compost that contains manure (or other animal products) is considered “untreated”. It therefore attracts the same restrictions as raw manure.

Compliant Compost is a new, simple code of practice that can be independently verified by approved auditors. The code is focused on demonstrating that the compost will not introduce human pathogens into the environment or onto food. Compost certified using the “compliant compost” program can therefore be used on farm without restriction.

WHAT TREATMENT PROCESSES CAN BE USED?A number of processes are used to break down raw organic materials into usable soil amendments. However, not all of these reliably destroy human pathogens such as E. coli, Salmonella spp. and Listeria

monocytogenes. Treatments that eliminate these organisms are essential if the raw materials include products originating from animals, such as manure, slaughterhouse waste or food wastes.

In-vessel composting

• Raw materials placed inside a vessel or contained space

• All materials heated to over 55oC for at least three days, or longer if food wastes are included

• Aeration provided by under-floor air injection system or turning inside a drum

Windrow composting

• Raw materials are formed into windrows (or piles)

• Composted for at least fifteen days with five turnings

• The centre of the windrow (or pile) allowed to heat to over 55oC for a minimum of three days between turnings

Only in-vessel and windrow composting create the high temperatures needed to destroy human

pathogens, so only these processes are used to make Compliant Compost.

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DOCUMENTING SAFE COMPOST PRODUCTION

NON-COMPLIANT COMPOSTS Vermicomposting

• Materials are fed to earthworms and excreta collected for use in soil

• Digestion by earthworms reduces, but does not eliminate, human pathogens

Anaerobic digestion

• Microbes are added to liquid slurries

• Biogas is produced along with solid digestate, which can be used as a soil amendment

• The effect of anaerobic digestion on human pathogens is highly variable

Ageing (static pile)

• Materials are simply placed in a pile to slowly break down

• Centre of the pile may become anaerobic (without oxygen)

• Uneven heating within the pile

• Human pathogens can survive for extended periods in unturned piles of organic materials

EQUIPMENT NEEDED ● Compost turner/windrow machine

● Loading equipment

● Temperature probes, ideally with data loggers

● Trowel, bucket, bags etc. for microbial samples

● Electronic or physical filing system to keep records

Compost windrow turners

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CALIBRATING THE TEMPERATURE PROBE/SNew temperature loggers are calibrated by the manufacturer. However, their calibration should be checked regularly, at least annually, to ensure the probes are still reading correctly. They can be returned to the manufacturer for this purpose, or you can check the calibration yourself using a bucket of melting ice (0oC) or simmering water (100oC).

Record the calibration date and result and add labels to each probe with the temperature correction needed. For example, if the probe reads 92oC in boiling water, add a label with “+8.0oC”.

RECORDING TEMPERATUREFor compost to be considered treated, the core temperature needs to reach over 55oC for at least three days on five separate occasions, with the pile turned in-between heating events. The graph below shows an indicative temperature profile. This ensures that every part of the material is thoroughly heat treated to kill human pathogens.

The exceptions to this are:

● If the feedstock does not include any materials of animal origin (including food waste) then only three heating events are required

● If the materials are inside an aerated vessel or

contained space, thus ensuring that all materials are at the same temperature, then three days at over 55oC is sufficient

• For example, mushroom compost spends 5-7 days at up to 80oC (phase 1) then 4-9 days at up to 60oC (phase 2). This treatment has been demonstrated to eliminate all human pathogens

Note that the reduced treatment time does not apply if food waste has been used as part of the feedstock.

MICROBIAL TESTINGCompost samples must be tested for E. coli (CFU/g) and Salmonella spp. (detected or not in 25g) by a laboratory that is NATA accredited to perform these tests. Suitable methods are petrifilm for E. coli and Vidas for Salmonella spp.

The compost samples must contain E. coli <100 CFU/g and Salmonella Not Detected /25g to be considered treated.

Microbial populations vary greatly within a pile. This is why compost needs regular turning ensuring that all materials are treated to eliminate human pathogens. However, the laboratory will only use a few grams of material for analysis. It is therefore extremely important that the sample you collect is representative of the entire batch. The more subsamples you take, the more likely it will be that your sample reflects the condition of the whole batch.

DOCUMENTING SAFE COMPOST PRODUCTION

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WINDROW TURNED

Temperature profile inside a compost windrow

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SAMPLING FOR MICROBIAL TESTINGThe best time to sample is immediately after the final turning. That is, once the pile has been turned five times if it contains manure, food waste or animal products; or turned three times if it only contains plant waste. It could also be sampled after loading for dispatch. This ensures the subsamples are already mixed, and so are representative of the whole batch.

It is more difficult to take a representative sample from a windrow or stockpile. More sub-samples need to be taken from a static pile compared to one which has just been turned.

Sampling after turning or loading (material is already mixed):

• Depending on the size of the batch, take at least five subsamples

• Break up any large lumps during sampling

• Combine the subsamples using a plastic bucket and mix thoroughly

• Place around 200g of the composite sample inside a plastic ziplock bag, then inside an extra bag to prevent leakage

• Keep cool and dispatch to the laboratory ASAP

Sampling from a pile or windrow:

• Depending on the size of the batch, take at least ten subsamples

• Using a steel or plastic trowel, dig down at least 20cm into the compost

• Alternatively, use an auger to drill into the compost, being sure to discard material from the top 20cm

• Collect samples from random positions along the pile or windrow, being sure to include samples from the top, middle and centre, and breaking up any large lumps

• Mix all subsamples thoroughly in a plastic bucket

• Place around 200g of the composite sample inside a plastic ziplock bag, then inside an extra bag to prevent leakage

• Keep cool and dispatch to the laboratory ASAP

DOCUMENTING SAFE COMPOST PRODUCTION

If using an auger, only use soil from >20cm deep inside the pile

Sample from at least 20cm inside pile

Combine all subsamples in a bucket and mix well

Sampling material from a windrow or pile for microbial testing

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PROPERTY MAPMost businesses will already have a property map. A simple, hand-drawn map is sufficient. The purpose of the map is to demonstrate that cross-contamination cannot occur between raw and treated materials.

Use the map to indicate where raw materials are delivered, location of windrows, drainage lines, leachate dam and loading area for the finished product.

Include locations of equipment. It is important that equipment used for handling raw or unfinished materials does not cross-contaminate the treated compost. Either use different equipment for raw and treated materials, or wash the equipment thoroughly before use.

DOCUMENTING SAFE COMPOST PRODUCTION

LOADING BAYS

WETLAND

RAWMATERIALS

MOUNDING

LEACHATEDAM

DRAIN

DRA

IN

BUNDEDWASH-DOWNAREA

SITE OFFICE

EQU

IPMEN

TSH

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SECONDARY

ACCESS

Example of a farm map

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DOCUMENTING SAFE COMPOST PRODUCTION

This project is supported by the NSW Environment Protection Authority as part of Waste Less, Recycle More, funded from the waste levy.

RECORD KEEPING A number of records must be kept to comply with the requirements of the Compliant Compost standard. Note that all records must be kept for at least two years.

PRODUCT COMPOSITION Record the raw materials used to make the compost. e.g. straw, poultry litter, vegetable waste

TREATMENT METHODRecord how the compost was made. For example:

• Aerobic composting using a windrow system• Aerated pasteurisation inside a closed vessel or contained space

START AND END DATEStart: Date when pile is initially created End: Date when composting criteria are met

DATE AND TEMPERATURE READINGSIdeally: Download from temperature data logger connected to a probe inserted into the windrow or pile, readings taken hourly. Alternatively: Manual temperature readings taken twice daily

BATCH IDENTIFICATION CODE Unique identification system for each batch

QUANTITY OF BATCH Estimated tonnes or m3

SUPERVISOR NAME Person responsible for the process

Records required to meet the requirements of the code of practice

WHO TO CONTACTThe Compliant Compost standard is managed by MRA Consulting Group www.mraconsulting.com.au. For more information, or to arrange an audit, please contact Virginia Brunton E: virginia@mraconsulting.com.au