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Biosolid Compost Project Heating Up

06 March 2013

Our Biosolid Composter is on its way to becoming fully operational in Whitianga with greenwaste now starting to be loaded into the machine.

The Biosolid Compost Project began in 2009 when it was identified that biosolids from the Eastern Seaboard Wastewater Treatment Plants (ES3) could be combined with greenwaste (garden waste collected from our Refuse Transer Stations after it has been through the mulching process) and turned into Grade Aa Compost.

After a successful trial at the Tairua Refuse Centre the composter was transported to Whitianga at the end of last year, where a larger, more fully operational model has been constructed.

It will now take six weeks for greenwaste inside the composter to reach a temperature of more than 55C to ensure good compost is made.

"The composter has to be stabilised at this temperature," says project manager Rob Paterson. "Inside the composter there is also a rotator, which will help oxygenate the greenwaste so we get the good bugs growing."

Once the greenwaste inside the composter is regulated to the right temperature, biosolids from the Whitianga Wastewater Treatment Plant can then be introduced. The hope is that this will occur in May.

"In Tairua it took about a month to get the composter heated to right temperature to produce compost.. Because this composter here in Whitianga is double that size we realise it will take longer," says Mr Paterson.

Greenwaste is currently delivered from Refuse Transfer Stations from Whitianga, Tairua and Pauanui and then loaded into the composter. The unit holds up to 45 tonne of compost and will run 24 hours, seven days a week.

(Above: Mulched garden waste from our Refuse Transfer Stations is transported to the Compost Site where it is put through a mixer-hopper machine and a trommel screen, that rotates to remove large chunks of wood, flax and rocks. The refined product is then loaded into the composter)


"For the first 8 months the compost we produce will be used on Council's parks and reserves," says Mr Paterson. "If there is a demand we expect to make the compost available to the public for use."

Construction of an odour room beside the composting unit should be completed in the next few weeks. This will allow trucks containing the biosolid waste to drive directly into the odour room and close the doors.

"The odour room is purely to contain unpleasant smells," says Mr Paterson.

The Biosolid Compost project has shown that composting of biosolids is the most economic and sustainable method of dealing with this type of waste, which is currently carted off the Coromandel and ends up in landfill.

To find out more about the Biosolid Compost Project take a look here.