Wellington City Council is laying out its choices for getting rid of the city's future rubbish.
Consents for the city's dump - the Southern Landfill in Happy Valley - expire in April 2026.
Four options, prepared by engineering firms BECA and Fichtner, include investing in: a waste incinerator, expanding recycling sorting capabilities, a treatment to dry and reduce biological material, or extending the existing landfill.
A fifth option tabled by councillors is for 'no landfill' - allowing the dump to close when its consents expire.
The landfill extension is council officers preferred solution.
In the City Council meeting agenda document prepared by officers, the extension is described as the most cost-effective.
The technological options are not easily scalable and are not alternatives to landfills on their own.
The extension is on a smaller scale, fitting within existing dump boundaries, than a controversial 2019 option that would have expanded the tip to within hundreds of metres of the Zealandia wildlife sanctuary.
And time is running out.
The agenda describes being at a "critical point" with the "shortest viable timeframe to design and implement the future waste disposal facility" before consents expire.
Council officers recommend starting the design and consent process for the landfill extension immediately.
Councillors will vote next Thursday on what options to take out to the public for feedback.
It is uncertain if the options will require rates increases.
The council's current waste approach requires a landfill to dispose of sewage sludge - the sludge must be mixed with solid household waste.
The council has already voted to invest in alternative sewage disposal technology, which should be in place by 2026, and would remove 20 percent of the waste going to landfill.
The funding of waste minimisation like curbside recycling financially dependent on landfill revenue.
A separate waste reduction roadmap being worked on by the council indicates it could halve volumes going into the southern landfill in the next 15 years.
The council has pledged to become carbon zero, and to reduce the amount of waste going to the landfill per resident a year from 600kg to 400kg by 2026.
Energy from Waste (estimate $214m to build, $15m a year to run. By-product: 25 percent)
Burns waste and uses the heat generated to produce electricity. Some of the ash produced can be used as a building material. Hot flue gases are treated to remove any pollutants.
Materials Recycling Facility (estimate $43m to build, $27m a year to run. By-product: 85 percent)
Takes in a combination of waste materials and sort them into different streams of recyclable materials. Left-over non-recyclable material can be sent to landfill or energy from waste.
Mechanical Biological Waste Treatment (estimate $78m to build, $24m a year to run. By-product: 65 percent)
Similar to the material recycling facility but with an added step of biological treatment such as bio-drying, composting or anaerobic digestion. This material is then sorted as in the material recycling facility.
Extension of existing landfill (estimate $57m to build, $4m a year to run. By-product: - )
The redevelopment of an existing landfill area and known as the 'piggy back option'. In this scenario, waste would be placed on top of a previously decommissioned stage of the landfill. Would give the Southern Landfill an additional life of 15-20 years, even longer as waste minimisation policies take effect.
'No landfill' (loss of revenue gathered from tip of $17m a year, likely 2.5 percent rates rise to cover kerbside recycling and other waste reduction initiatives).
This option involves closing the Southern Landfill when consent runs out in 2026, and turning it into a reserve or similar. Wellington City's residual waste would need to be disposed of at other landfills in the region, for example in Porirua or Upper Hutt.