Processing Greenwaste and Producing Compost

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Processing community green waste and turning it into organic, nutrient-rich compost has always been Composting New Zealand’s central value proposition.

But if we’re honest, we can understand why there is a public misconception of “double dipping” in the green waste processing and composting industry.

It is often implied that there are questionable ethics at play in charging customers to “drop off” their garden waste and then charging once again to sell it back to them as compost.

greenwasteAt Composting New Zealand we are open and transparent about our business processes and recognise the value in keeping our customers informed.

This post aims to demonstrate why there is a cost for disposal of green waste at our locations, and explains the lengthy and laborious processes we undertake in order to produce our quality organic products.

For a simplified breakdown of our greenwaste-to-composting process, check out our recent infographic.

How does the composting process work?

At Composting NZ we accept in all our green waste from our local communities. Our customers bring in their lawn clippings, shrub prunings and plant garden waste via wool sacks, car boot loads, trailers and trucks.

Garden waste left at our satellite branches is routinely collected and returned to our primary yard in Kapiti, where all green waste is processed.

We ask our customers not to mix any household rubbish in with their green waste and to check that any herbicide sprays they use on their gardens do not contain picloram, clopyralid, aminopyralid or aminocyclopyrachlor. These four chemicals are usually found in herbicides/sprays only available to licenced applicators and DO NOT break down in the composting process.


From the beginning

The large green waste pile is regularly mulched using our state-of-the-art Shark Willibald mulcher. Mulching (shredding) assists in the mixing of the feedstock and reduces the composting time of the piles.

During the mulching stage we are busy combining the different feedstocks (ie carbon-nitrogen) to achieve the correct “compost recipe” for effective composting.

The mulched green waste is formed into windrows of optimal height, width and length at the rear of our Kapiti site.

“Anything of quality takes time and so it is with making compost”

Weekly monitoring of the pile temperatures using a handheld probe and digital thermometer allows us to monitor the ‘health’ of the compost piles and alerts us to any corrective action that may be required.

Some piles may be in need of additional moisture, the pile heights may need to be increased or decreased or they may require more frequent turning.

For more information on our compost products, click below.

Active composting

During the active composting stage (first month) all the piles will be turned twice a week using our new Willibald windrow turner.

This allows the material on the outside of the pile to move into the centre (heated core) of the pile, fluffs the material so the air can move more freely through the pile and reduces the size of the particles.

What’s next?

Once the piles have completed their active composting stage and met all the temperature requirements, they will be screened to remove the oversize material and then like a good wine, left to mature.


Click on the image below to be taken to a simple slideshow that walks through our commercial composting process from start to finish, and back round again!

Composting NZ infographic

How do we know it’s a quality product?

When the whole process is completed we carry out in house growing tests on all our batches to ensure our customers are consistently buying quality products.

Random batches are also regularly selected for off-site testing with samples sent to Hills Laboratories in Hamilton. These samples are tested for a variety of profiles important to CNZ and our customers. These include heavy metals, nutrient levels, pH and if any herbicide/pesticide residues are detected.

To see our latest lab results, click here.

See for yourself!

We welcome visitors who wish to come and take a look at our green waste and composting process in action.

Contact the office and we’ll be happy to book you in for a quick tour so you can see the extent of the work that goes into what we do here at our main Kapiti branch.