What is residual waste?

    Residual waste is waste that can’t be re-used or recycled and needs to be disposed of. In Wellington City, residual waste (which includes household and industrial waste) goes to landfill.

    Why are you looking at future residual waste disposal options for Wellington City?

    Residual waste is currently disposed of at a Council-owned facility, the Southern landfill.  

    The Southern Landfill receives almost all of Wellington City’s dewatered sewage sludge as well as a large portion of the city’s residual waste, including the city’s kerbside rubbish collections.  

    The city’s dewatered sewage sludge needs to be mixed with waste for safe disposal at the Southern Landfill. Revenue generated from the landfill also pays for the kerbside recycling service as well as subsidising waste minimisation initiatives and activities.    

    The current consents for the Southern Landfill expire in April 2026, so we need to explore how we dispose of the city’s residual waste after this date. The first phase has been completed, with multi-criteria analysis used to create a shortlist of potential waste disposal options and solutions.

    What happened to the previous engagement around the Southern Landfill extension?

    In 2019, we engaged with the community on a proposed extension of the landfill after the existing consents expire. This attracted a high level of interest and resistance, including: 

    Concerns the engagement process didn’t follow provision of the Local Government Act 2002.

    • Community concerns about the potential effects on the environment.
    • Residents’ groups concerned about traffic and other potential effects.
    • Concerns that the engagement process wasn’t sufficiently extensive.
    • Concerns that the Council might be seeking to maximise waste and revenue.
    • Residents seeking a better understanding of the relationship between landfill and sludge.

    We listened to these concerns, and agreed to delay any further planning for the landfill extension until a decision was reached on sludge. 

    In the 2021 Long Term Plan, the Council committed to funding a sludge minimisation solution. This decision has provided more clarity, although it is only the first step in a long process with other risks that could delay or derail the preferred sludge minimisation project.  

    In the meantime, the Council has engaged Beca Consultants and Fichtner Engineering and Consulting to identify and assess alternative waste disposal technologies. 

    We have now reached a critical point as we have the shortest viable timeframe to design and implement the future waste disposal facility before April 2026.

    What are the five waste disposal options?

    BECA Consultants and Fichtner Engineering and Consulting have shortlisted four options: 

    Option 1: Energy from Waste
    This method burns waste and uses the heat generated to produce electricity (and possibly heat). The output is ash which has a significantly reduced mass and volume compared to the input waste. Some of the ash can be used as building material.  

    The hot flue gases produced from the combustion of waste are passed through a boiler which superheats steam to a high pressure which drives a turbine to generate electricity. 

    The flue gases are then treated to remove any pollutants before they are emitted to the atmosphere.

    Option 2: Materials Recycling Facility 
    MRFs take in a combination of waste materials and sort them into different streams of recyclable materials. Typically, household waste is sorted into ferrous, non-ferrous, glass, paper and card, and plastics which can be sent off the be recycled at another facility. The left-over non-recyclable material can then be sent to landfill or energy from waste.

    Option 3: Mechanical Biological Treatment
    MBT is similar to the material recycling facility but with an added step of biological treatment such as bio-drying, composting or anaerobic digestion. This approach is more common when the input material has a high organic content.  

    In terms of bio-drying, waste is put into piles with a controlled air flow which decomposes the waste, heating it in the process which reduces the moisture content and produces a more homogenous material. This material is then sorted as in the material recycling facility.

    Option 4: Extension of existing landfill
    We took the feedback from the engagement we did with key stakeholders in 2019 and 2020, and considered other possible options for a landfill on the same site. These options seek to minimise the environmental impacts in terms of native regenerating vegetation, and associated native species (such as birds) and the Carey’s gully stream. We’ve determined that the area known as Stage 2 would be suitable for a smaller landfill, that would give us approximately 15 years, and have a lesser environmental impact.

    A fifth option
    At a briefing on 24 August, Councillors requested that a fifth option, ‘no landfill’, be considered:  

    Option 5: No residual waste facility in Wellington City
    This option would involve 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.

    Why do Council officers think that a landfill extension is likely to be the preferred solution?

    The landfill extension is likely to be the officer-preferred solution for the following reasons:  

    • All the technological waste disposal options require a landfill to receive un-processible waste, and by-product. These technological options are not alternatives to a landfill on their own. 
    • Technological options require a minimum level of feedstock to operate and are not easily scalable.
    • Technological options make it convenient to continue to dispose instead of more preferred options higher in the waste hierarchy.
    • The landfill extension is the most cost-effective option, particularly given the financial impacts of operating waste minimisation services without this revenue if all waste was exported. 
    • By retaining control of a landfill, the Council can implement tip-face waste minimisation policies, as well as directing revenue from the landfill into supporting general waste minimisation policies. 
    • Exporting waste will reduce regional landfill capacity and incentivise the development of further regional landfills. 
    • Exporting waste risks Wellington City being perceived as being unwilling to deal with its own waste. 
    • The landfill can always be closed before it is full if it is unnecessary. 

    Why are Council officers recommending starting the design and consent process for the landfill extension? Has a decision already been made?

    To minimise risk of delay, it is prudent to begin the design and consenting process as soon as possible. Whilst we accept that this is not ideal, we will continue to investigate and analyse further waste minimisation and waste disposal options and consultation requirements. This will ensure that all reasonably practicable options are available for the Council’s consideration of the issue of the disposal of residual waste beyond 2026.


    How were the options shortlisted?

    First of all, a longlist of 14 waste management options were assessed and scored against the following criteria: 

    • Can the technology be successfully implemented prior to the expiry of the consent of the Southern Landfill (June 2026) or by the time the current landfill reaches capacity, whichever occurs first?
    • Is the technology mature, and are there sufficient examples of this technology being applied at sale either in New Zealand or internationally?
    • Is the technology scalable, and will it be able to adapt given the uncertainty in waste generation in the Wellington region going forward?

    From these, four options were shortlisted. All of these demonstrated:

    • Strong international track record for handling solid waste
    • Minimal effects on surrounding communities in terms of odour and particulate emissions
    • With the exception of landfilling, all options reinforce a circular approach to waste management where material is diverted from landfill and generates value.

    Where does sludge fit into the picture?

    Wellington’s sludge is currently disposed of at the Southern Landfill by mixing it with household waste. Due to operational requirements and engineering stability concerns, this has to be at a ratio of no less than 4:1 solid waste to sludge.  

    In the 2021 Long-term Plan, the Mayor and Councillors decided to invest in alternate sewage sludge disposal technologies to break the link between the landfill and sewage. Without the technologies necessary to reduce sewage sludge, we won’t be able to achieve our waste and carbon reduction targets. It is anticipated that alternative treatments for sludge will be in place by 2026.

    Find out more about the sludge minimisation project

    What is Wellington City Council working on in the waste space?

    We are currently undertaking two separate but interrelated projects:

    •  Wellington City’s Strategic Waste Review and subsequent development of a waste minimisation roadmap for waste – He Ara, He Para Iti/A Pathway, Minimal Waste.
    • Wellington City’s Future Waste Disposal.

    Why is Wellington City Council carrying out a strategic waste review?

    Our current approach to waste management doesn’t reflect best practice and we need to make some big changes, so we’re prepared for the future. Our current approach to waste minimisation is currently constrained by sewage sludge management and the need to run a landfill to dispose of sludge. Plus, our existing funding policy means that waste minimisation activities are financially dependent on revenue from the landfill. We need to break this link.   

    Additionally, the Council has adopted Te Atakura - the blueprint for the city to be carbon zero, and a Regional Waste Management and Minimisation Plan - where we have committed to reducing the amount of waste going to landfill from 600kgs per person per annum to 400kgs per person per annum by 2026. These commitments, along with increasing expectations from our residents to reduce the amount of waste going to landfill, mean we need to review our current and future relationship with waste. 

    What will the strategic waste review do?

    The preliminary findings of the review highlight a need for Wellington City to refocus its role and efforts in relation to waste minimisation. 

    Additionally, the review process confirmed there was a need to develop a clear and actionable plan to enable Wellington to become a leader in minimising the use of resources and maximising reuse and recovery, including detail on how this should be delivered and funded. 

    The roadmap will allow the Council set priorities on the types of waste it wants to target to divert from landfill in future years. Priorities will be implemented through a waste minimisation roadmap investment plan that will include timing, resources and financial investment required to achieve each diversion initiative.  

    The draft roadmap sets out three objectives:  

    • Ōhanga āmiomio (circular economy) - To mitigate the environmental impacts of Wellington City by reducing resources used and increasing reuse and recovery of resources.
    • Kaitiakitanga whakanaonga (product stewardship) - To enable and partner with communities and businesses to reduce resource use and waste.
    • Whakahaere hūrokuroku i te para (sustainable waste management) - Manage any remaining waste in the most sustainable way according to the principles of the waste hierarchy

    The draft roadmap will be presented to the Infrastructure Committee on 14 October 2021, and asks the Council to agree in principle to the roadmap. 

    What is the difference between the Waste Minimisation Roadmap and the Council’s Waste Management and Minimisation Plan?

    The Council is legally required to have a Waste Management and Minimisation Plan (WMMP).  The Council’s current WMMP will lapse in 2023. The roadmap exists as a strategic waste planning tool, that will allow the Council to plan and potentially secure funding for future WMMP projects.  

    The Council will have opportunities to consider, debate and potentially amend the breadth of the waste minimisation projects proposed, as the broader programme of works is advanced with the Council as part of the development of the next WMMP.

    Does the Strategic Waste Review and the subsequent Waste Minimisation Roadmap for waste mean my rates will increase?

    We are unsure at this stage. The roadmap does provide avenues for the Council to promote a step change in waste minimisation.  It allows for waste minimisation initiatives to be considered, discussed, debated and where required, consulted, prior to approval. Any costs and funding options for such initiatives will be part of this process.