sampling methodology

i n f o r m a t i o n s h e e t

Purpose

To assess adequate pathogen reduction of compost to meet NSW Food Waste Compost Exemption pasteurisation requirements.

When to test With the right equipment (augers), this test can be done prior to screening. If this test is done after screening, it is important to wait at least a few weeks to make sure the pile heats up again and then cools down. Screening disturbs the compost and exposes the pasteurised compost to E-coli and other pathogens in the general environment, on the screening equipment, in the air and on the ground.

General comments

Pretend you are performing open heart surgery. E-coli is everywhere, except inside your finished compost. If tools are accidentally placed on the ground, on the covers or touched by humans, they need to be sterilised before being used again in the pile. The opportunity for cross contamination is significant.

What you need:

ideally 2 workers (possible with one but takes longer)

2 x stainless steel buckets (milking buckets)

steel tipped Spiral Auger1

stainless steel Jarret Auger2

a small stainless steel shovel or trowel to remove top surface of compost

small Jimmy bar or spoon or similar to assist removal of sample from Jarret Auger3

approx 5 litres hydrogen peroxide 5%4

gloves, mask and Personal Protection Equipment (PPE)

labelled sterile screw top soil sample jars

foam esky and ice bricks

heavy duty scrubbing brush for cleaning tools at end5

permanent marker, sticky tape and either express post or courier bag

access to wash basin, water and soap.

}

}

}

}

}

}

}

}

}

}

}

}

}

1 Available from Dormer: www.dormersoilsamplers.com/ 2 Available from Dormer: www.dormersoilsamplers.com/ 3 Available from Dormer: www.dormersoilsamplers.com/4 Available from Commercial Cleaning Supply or Chemical Companies. 5 Available from Commercial Cleaning Supply or Chemical Companies. 6 P54.

What you do:

Remove covers

Pour hydrogen peroxide into one bucket. Swish around and then pour into next bucket. Let first bucket dry.

First bucket will be for samples. Second bucket is to wash tools.

Place ALL tools (or active ends) into second bucket to coat in hydrogen peroxide.

Remove tools only as needed. Ensure tools do not touch each other or any surface on site other than that to be tested.

Put on sterile gloves. With a hand tool, scrape surface of compost pile aside .

With spiral auger, make hole into compost pile.

With Jarrett auger, insert into hole and take compost sample.

Empty Jarret auger sample into first bucket. Use Jimmy bar (sterilised metal rod) to assist if necessary. Do not place metal rod on ground. Place in bucket if you need to put aside.

Do not let hand tool touch augers. Wash tools in hydrogen peroxide bucket if cross contamination occurs.

Continue sampling procedure at least 5 times. (The Biosolids Guidelines say minimum of 5 samples with each sample representing no more than 100 tonnes of product6. The more samples taken, the more accurate the end result will be.

Mix samples with either clean tool or clean gloves. Fill sample jar with composite sample. Seal, label and place in esky with ice brick. Seal esky, pack and send to laboratory with appropriate paperwork ensuring arrival within 24 hours. Minimum sample size is 300 grams.

If you take enough samples, leftovers can be used for the tests outlined below.

Clean tools. Dispose of hydrogen peroxide appropriately.

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

Pasteurisation/Pathogen Reduction/Microbial Stabilisation

Alternative: we have been experimenting with using a trigger spray pack for hydrogen peroxide instead of the second bucket to reduce costs, but haven’t done a complete test just with this method yet.

Sample size

Each grab sample can represent a maximum of 100 tonnes. So if you have 1000 tonnes of finished compost that you want to test, you need to take a composite of 10 samples – one from each 100 tonne section. Batches of finished compost can be stockpiled and amalgamated into larger batches to reduce testing frequency. For smaller sites with plenty of room to stockpile finished compost, you may only have to test compost once a year when you are ready to go to the market with your finished compost.

Process for AS4454 and NSW Biosolids Chemical Contaminants and Heavy Metal Tests and SWEP testing

What you need:

Same as above but without need for infection control, sterilisation or refrigeration.

What you do:

Same as above but without need for keeping tools sterile.

No need for refrigeration.

Samples can be placed in A4 resealable plastic bags.

Minimum sample size for AS4454 is 6 litres but 8-10 litres is recommended.

Minimum samples size for Biosolids Contaminants and Heavy Metals is 500 gms

Minimum sample size for SWEP compost analysis is 200 gms.

Sample size. Each grab sample can represent a maximum of 100 tonnes. So if you have 1000 tonnes of finished compost, you need to take a composite of 10 samples – one from each 100 tonne section.

}

}

}

}

}

}

The NSW Biosolids Guidelines go into some detail about sampling frequency, statistics and minimum batch sizes. If you are someone that understands the maths, you could reduce the amount of sampling you have to do over time by making use of history or probability or co efficient thingies outlined in the NSW Biosolids Guidelines.

Disclaimer

This information sheet summarises how folks involved in the Groundswell project understand and meet the legal framework that regulates the application of food waste compost to land. It should be used in conjunction with the Groundswell information sheet on Compost Regulations. As regulations change, this information sheet may be out of date. Please be smart and work with your local EPA to make sure you are doing the right thing.

Also, there is no getting round it. You are still going to need to read the Food Waste Compost Exemption, the Biosolids Guidelines and the AS4454 Compost Standard.

Bibliography

ARMCANZ – Australian Guidelines for Sewerage Systems - Biosolids Management, 1995, ARMCANZ Water Technology Committee, Canberra.

NSW EPA – Environmental Guidelines - Use and Disposal of Biosolids Products, reprinted December 2000.

Protection of the Environment Operations (Waste) Regulation 2005 – General Exemption Under Part 6, Clause 51 and 51A – The Food Waste Compost Exemption 2008. Available online at: www.environment.nsw.gov.au/resources/waste/ex08foodcompost.pdf

Resources and Links:

Dormer: www.dormersoilsamplers.com

SWEP Analytical Laboratories: www.swep.com.au

Sydney Environmental and Soils Laboratory: www.sesl.com.au

For updates and more information on the Groundswell project go to: www.groundswellproject.blogspot.com

Written by Simone Dilkara, 2010. Graphic design/illustration by Carolyn Brooks

This work is licensed under the Creative Commons Attribution 3.0 Unported License and can be reproduced providing the Groundswell project is acknowledged as the original source.

The Groundswell Project was assisted by the NSW Government through its Environmental Trust