Biosolids Compost Project

The reality is the composter is costing ratepayers a considerable amount to run and it's just not financially viable.

It was purchased as a second-hand machine, so the plant is starting to age, we're spending tens of thousands in maintenance and depreciation and the costs are just outweighing the benefits.

Our Council has taken careful consideration to reach the decision to close the plant. Including:The volumes of bio-solids able to be accepted are relatively low (40 tonnes per month) at peak capacity.

The asset is starting to age so in addition to repairs undertaken last year, there needs to be an additional $40K spent on maintenance and eventual asset renewal would be required.

Operating costs are in excess of $220K per annum. When the composter was first set-up as a trial back in 2007, there were assumptions that fuel costs and landfill costs would rise, which meant composting bio-solids would be financially beneficial. In reality, transport and fuel costs haven't increased in the past 10 years as expected.

Over the past three years Council staff have investigated potential commercial markets and modelled financial results and future viability, all of which has proven it is not financially viable.

The composter started out as a trial back in 2007 with Council publicly signalling it would keep reviewing the viability of the composter to see whether it was cost effective.This included an independent report commissioned in 2014, which found there was no significant financial benefit to retain the composting operation.

Following that report, Council asked staff to come back with more detailed figures on compost volumes, along with a decommissioning plan for the composter and possible options for re-use of the Whitianga site.

We didn't want to make a snap decision so staff went away to conduct a 12-month trial to determine viabillity. That got extended to nearly two years and after looking at all the details again, nothing significant has changed.

Getting enough green waste into the composter isn't the problem - even with a more than adequate supply of greenwaste, the composter plant cannot process a high enough volume of bio-solids to be economic based on the costs required to operate.

The closure of the plant was on 2 October 2017 with community and stakeholders given time to be made aware of the decision. We have also been communicating with stakeholders individually.

We are now in the process of decommissioning the plant, with a number of options available around this.We are not ruling out that we will be able to do some form of composting in the future, which we hope will involve regional support, or cost-sharing benefits with other councils



Reports on the viability of the composter

To read the report click here to view the Infrastructure Committee page. Go to 29 October 2014 meeting P16.

To read the 2015 report click here and go to the Infrastructure June 2015 Committee meeting item 3.8

You can also download the original 2007 Business Case on the Biosolid Composter from the right-hand side of this page.



  • 2007 - Council started investigating how we could sustainably manage and investigate environmental benefits using biosolids taken from our Wastewater Treatment Plants on the Eastern Seaboard.
  • 2009 - An 18-month temporary trial was set up in Tairua to see if it could produce Grade Aa compost that we could use on our parks and reserves. This was successful.
  • 2012 - The plant was moved to a permanent site in Whitianga and part of the resource consent was that Grade Aa compost had to be made, which for the first eight months could be used only on our parks and reserves. (This was also successful).
  • 2014 - As part of our 2015-2025 Long Term Planning our Council reviewed the viability of the composter, and commissioned an independent report to assess the cost benefits. The report was presented to Council's Infrastructure Committee in November 2014 and suggested there was no significant financial benefit to retain the composting operation and it was more cost effective to dispose of bio-solids to landfill rather than compost. Council's Infrastructure Committee resolved at its meeting in October 2014 that staff should come back to the Committee in 2015 with detailed figures on compost volumes, along with a decommissioning plan for the composter and possible options for re-use of the Whitianga site. It also recommended Council's Audit Committee consider any future financial risk to ratepayers.
  • 2015 - A report to the Infrastructure Committee in June showed that there was a potential commercial market identified and that the 2014 assessment incorporated a number of scenarios, which modelled financial results that may not have fully reflected the financial viability of the activity. You can read the report here (item 2.2). Council agreed that our contractors Veolia take over management of the composter with the aim of producing financially viable Grade Aa compost for the public to purchase. Meanwhile investigations would begin to see if any commercial business would invest and to reassess in 12 months' time, the commercial viability of the composter. This trial was twice extended to an eventual 24 month period.
  • 2017 - Report goes to Infrastructure Committee with staff recommendation to cease operations at the composter as the operational costs outweigh savings. Council endorse Infrastructure Committee's recommendation


Image of the composter based at Whitianga

(Above) Image of the composter based at Whitianga.


The Biosolids Management Strategy

A strategy and long term project was developed in parallel to the ES3 project, which culminated in the Biosolids Management Strategy (BMS) adopted by Council on 28 June 2006.

The BMS showed that the composting of biosolids was the most economic method of dealing with biosolids. The option was also attractive from a sustainability point of view and created economic value from a waste product, that would otherwise end up in the landfill.

The 2009 Trial

The Biosolid Compost Project commenced with a trial at the Tairua Refuse Transfer Station (RTS) to show that the production of biosolid compost would attain Grade Aa status and be cheaper than the current carting and disposal costs to landfill.

The BMS review took place at the end of the product verification process of the trial in December 2009 and its findings along with potential options were reported to us in February 2010.

A report to Council on 16 August 2010 confirmed that the trial was successful, that the composting process achieved Grade Aa status and that the cost of producing biosolid compost was below the agreed target of landfill operation cost + 20%

The outcome of the trial highlighted that composting was still the best solution for the sustainable management of biosolids.


Frequently Asked Questions

What are biosolids?

Biosolids are the 'solids' that are screened out of the ES3 plants, before the liquids are treated. For more information about the treatment process, please visit this page and download the ES3 brochure.

What is Grade Aa compost?

This is the highest grade (safest and highest quality) of compost possible using biosolids according to the NZ Biolsolids Guidelines. It is a grade that means it can be used on gardens safely.

What is ES3?

ES3 stands for "Eastern Seaboard 3", the name of the project to develop 3 new generation waste water treatment plants at Tairua, Whangamata and Whitianga.

What is the BMS?

BMS stands for Biosolids Management Strategy, which was developed inconjunction with the development of the ES3 project to allow us to develop a process for dealing with the biosolids from these new treatment plants.

Why are we doing this?

The project aims to save the ratepayer money in the long-term by taking biosolids out of landfill by turning it into Grade Aa compost that can be used on our parks and reserves and by the residents of the Coromandel on their gardens.



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