Mixed organics (both garden and food waste) are collected as normal through the kerbside service. The mixed organics are taken to a transfer station. The transfer station could be inside the enclosed processing hall at the existing plant or at an alternative enclosed facility. Organics are then loaded into trucks and delivered to the composting processor/s. A small portion could be sent to community gardens.

The diagram shows how this option would work if a processor could take the full amount of mixed kerbside organics.

We looked at alternative composting plants and worm farms throughout Aotearoa New Zealand.

At the time of this consultation, no alternative South Island processors have the capacity or resource consent to take our mixed kerbside organics (55,000 tonnes per year). They may be able to get resource consents and operate in the future.

There are North Island processors who, between them, could take a large proportion of our kerbside organics (approximately 46,000 tonnes) under their existing resource consents. This would mean transporting kerbside organics to various locations in the upper North Island.

In time, a North Island processor may be able to receive all our kerbside organics, if one of them gains the necessary resource consents.

Whether all our kerbside organics are processed by one or several alternative processors, either in the North Island or locally, additional resource consents will be needed. This process, and the need for processors to upgrade, mean it is unlikely this option could be in place before late 2025.

All implications shown below (effect on rates, emissions, etc.) are based on sending the full amount of mixed kerbside organics to North Island processors. We calculated the implications over five years, because this is the estimated timeframe until a permanent solution is up and running.

Risk of offensive and objectionable odour from the plant affecting local community

What we do now: Medium to high risk.

This option (if still processing some organics at our plant up to 2025): Medium risk.

This option (if not processing any organics at our plant): No risk.

Implementation time

Full amount not until late 2025, with 9000 tonnes going to Kate Valley Landfill or processed at the existing plant until then.

Estimated cost (over five years)

What we do now: $112 million

This option: $262 million to $278 million ($150 million to $166 million more than the existing five-year cost)

Estimated effect on rates (over five years)

What we do now (expected rates portion for 2023/24 per household): $116. This is a fixed cost that everyone pays, which covers the cost of collecting and processing organics. This is a proportion of the total amount you pay for your kerbside recycling and organics service.

This option: 3.7% to 4.1% increase – this is the annual rates impact over five years.

Dollar amount: $1435–$1525 over five years. Cost per year is $287–$305. (Exact amounts would be finalised in the 2024–34 Long Term Plan process.)

Estimated greenhouse gas emissions (generated over five years)

Greenhouse gas emissions are measured in carbon dioxide equivalent (CO2-e). This measure combines the effects of different emissions, such as methane and carbon dioxide.

What we do now: 48,232 tonnes of CO2-e over five years.

This option:

North Island processors (excess organics processed at the Organics Processing Plant in the interim): 48,611 tonnes of CO2-e, an increase of 379 tonnes CO2-e.

North Island processors (excess organics sent to Kate Valley Landfill in the interim): 56,522 tonnes CO2-e, an increase of 8290 tonnes CO2-e.

Read more about how we calculated our greenhouse gas emissions on the main project page.

Alignment with sustainability policies

Along with central government, we have policies and strategies for managing organics.

What we do now: Aligns

This option (North Island processors and OPP): May not align due to increased transportation emissions.

This option (North Island processors and Kate Valley Landfill): May not align due to increased transportation emissions and disposal to landfill.

You can read these policies and strategies on the main project page.