Mixed organics (both garden waste and food waste) is collected as normal through the kerbside service and taken to the existing plant for the first composting stage to be done indoors. This involves blending mixed organics with green waste, shredding the material then moving material into indoor composting tunnels.

The partially composted material is taken to a local processor who completes second-stage composting – maturation and screening. It could take 6–12 months for a local processor to be operational and able to do this.

The diagram shows how this would work.

Risk of offensive and objectionable odour from the plant impacting on the local community

What we do now: Medium to high.

This option: Very low – no outdoor storage and material not being moved between buildings.

Implementation time

Six to 12 months. Several local processors have indicated an interest in providing second-stage composting. Our assessment is that they could be operational within six to 12 months.

Estimated cost (over five years)

What we do now: $112 million.

This option: $144 million ($32 million more than the current five-year cost).

Estimated effect on rates

What we do now (expected rates portion for 2023/24 per property): $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: 0.8% increase – this is the annual rates impact over five years.

Dollar amount: $760 over five years. Cost per year is $152. (The exact amount would be finalised through 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.

This option: 48,336 tonnes CO2-e, an increase of 104 tonnes CO2-e. This option has the lowest increase in emissions overall, as the majority of the organics will be processed locally.

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: Likely to align – most organics are composted, with only a small amount going to landfill for a short time.

Read these policies and strategies on the main project page.