The future of the Southern Landfill

When we put waste into a landfill, our microbial friends naturally start eating up the waste. As they consume the waste, they tend to produce methane as a by-product, i.e. they tend to fart a lot, similar to what happens in a cow’s stomach.

It is important to point out that this is a natural process that occurs to anything organic we throw away and allow to decompose, regardless of whether it is in a landfill or in your backyard.

Generally methane is contained within a landfill by the placement of a clay cap, a layer of clay that we place above the waste that contains the gasses within the landfill.

This ‘cap’ is not completely airtight and as the gas builds up under it, some of the landfill gasses escape into the air. This can cause unpleasant odours but more importantly, it also allows methane, a known greenhouse gas, to escape into the air.

Methane is about 100 times worse as a greenhouse gas than carbon dioxide. At the Southern Landfill, we recognise this is not ideal for the environment and our neighbours.

The Wellington City Council and its partners, Nova Gas, have installed gas wells to ’suck ‘ the gas through pipes and burn it in a generator to produce electricity, much like a petrol generator. The generation process does produce carbon dioxide but this is much better for the environment than releasing methane.

We currently have around 16 operating gas wells around the various stages of the landfill powering a 1 Megawatt generator that sends the power into the national electricity grid to power up houses heating and electric cars/buses.

As a landfill gets older, it produces less and less methane as the bugs eat all the waste. Over a period of 50 years, we expect landfills to produce only small amounts of gas and to ‘stabilise’. Because of this, over time it may become uneconomic to continue to suck the gas to produce electricity at the Southern Landfill.

When this occurs, the land can be repurposed for other uses but not housing. Most sports playing fields in Wellington are built on old landfills. With the appropriate infrastructure and a bit of work, these old landfills can be used as recreational areas for everyone to enjoy.

Waste comes to us from various sources. For some waste there is no alternative because it’s too dangerous to handle, e.g. asbestos waste, and the Southern Landfill is the safest disposal site.

For other waste, like kitchen waste or construction waste, there are alternatives to landfilling but the challenge is for industry to set up affordable processing schemes and for us to support these initiatives when they become available.

Regionally, we currently send 600kg of rubbish per person to landfills every year. Some of this waste could potentially be diverted but either the disposer decides not to separate out the recyclable waste or there are no readily available diversion options.

The Landfill is the ambulance at the bottom of the cliff. Once the rubbish gets here, we have to accept it and deal with it.

We can all do more to reduce our waste, but it takes a concerted effort and we may have to change the way we act and how we live.

A good starting point is to change the way we purchase our groceries. Only buy sufficient food for the week, shop to menus, purchase choices without excess or any packaging. This reduces food and packaging waste.

Other ideas include:

• If you have a garden, home composting of your food scraps.

• Separating out the recycling correctly – kerbside recycling is provided in Wellington City. This reduces material that could have been recycled going to Landfill.

• Drop off e-waste for free at the Southern Landfill.

• Re-use, refurbish or resell old furniture.

• Fix appliances rather than buying new ones. Check out the Tip Shop account on Trade Me, we sell a whole lot of spare parts for vacuum cleaners and computer parts.

To find out more about recycling in Wellington City go to https://wellington.govt.nz/services/environment-and-waste/rubbish-and-recycling/top-tips-for-rubbish-and-recycling

For more about the Tip Shop visit https://www.facebook.com/TipShopWellington/ or https://www.trademe.co.nz

During our conversations with you there have been some recurring topics of interest. We’d like to dive into some of those.

The top three topics so far are waste minimisation, environmental and community impacts.

Under the waste minimisation banner, you’ve talked a lot about the sewage sludge processed at the Landfill. You’re interested in the sludge volume, handling and treatment, and whether there are any opportunities to compost sludge.

Other issues of interest have been the circular economy, product stewardship, recycling plastics, waste collection, green waste, container return schemes, construction and demolition waste and waste recovery.

Environmentally, aquatic impacts are top of the list in relation to Ōwhiro stream, Taputeranga Marine Reserve, and landfill design so as not to leach contaminants into the stream.

The community impacts raised are around traffic and road issues on Happy Valley Road, the cumulative effect of the three landfills in the area (Council’s Southern Landfill and two privately owned and run landfills) and the Southern landfill capacity and lifespan.

We’ve been keeping a record of all of the feedback so we can consider it in our waste management alternatives assessment and so it can help inform any of the technical studies we will need to do.

Below are a few of the questions we’ve received (and the answers!).

Are there any plans to compost sewage sludge?

We do not have plans to compost sewage sludge at this stage. We have done so in the past and it was not successful. It was costly to produce, there were many complaints about the odour, and it was not marketable as many people were opposed to the idea of composted human waste. Wellington Water is looking at options for sewage sludge handling, treatment and disposal.

Is the Landfill affecting the water quality for the stream and marine reserve?

The Council monitors water quality through monthly water sampling around the stream (Carey's stream) that runs through the Southern Landfill as part of our existing consent.

According to our annual compliance report from the Greater Wellington Regional Council, reviewed by an independent expert, the expert surmised that the Southern Landfill does not appear to be causing even minor adverse effects on water quality.

Instead of extending landfills, can you look at alternatives that involve reducing the amount of waste created in the first place?

We are committed to trialling a kitchen waste diversion scheme due to start in May next year. We also strongly encourage the use of reusable alternatives rather than single-use and degradable options and we fund sustainable initiatives with grants including the Waste Minimisation Seed Fund which you can learn more about here: https://wellington.govt.nz/services/community-and-culture/funding/council-funds/waste-minimisation-seed-fund

Wellington (and NZ in general) could really do with recycling solutions for food waste and soft plastics. It would be good to see Wellington City Council take the lead on this.

Council is committed to a trial of kitchen waste diversion as mentioned above. The soft plastic scheme is due to re-start again in selected stores in Wellington and the Hutt Valley from October. Head to https://www.recycling.kiwi.nz/solutions/soft-plastics/ to find out more.

The number of construction demolition trucks on the road to the Landfill is around 1000/day. It’s impacting on our mental and physical health. Also during winter there is lots of mud trucking up and down and pollution from uncovered loads. What can be done about this?

The Southern Landfill requires that all trucks must undergo wheel washing before they leave the site to minimise the amount of mud on the local roads.

Regarding uncovered loads, we are looking at a campaign both locally and within the Landfill to raise awareness and improve the efficiency of the covers. It is hoped that this will decrease the number of uncovered or poorly covered loads. Although this will be around trucks coming to the Southern Landfill, we are investigating ways of having a wider impact in order to reach trucks that are coming to the other two neighbouring privately run landfills.

As part of any consent application we will be looking at the number of trucks using the local roads and how many of those are coming to the Southern Landfill and how many are visiting C&D Landfill and T&T Landfill. That way we will have specific information to work on.

With room for our rubbish running out we think extending the Landfill is the best way forward to manage our waste, but we are testing this assumption by looking at what alternatives are around.

We’ve had some lively debates with the community around these different technologies so though it might be handy to summarise them here for you.

The relatively small size of Wellington and our typography gives us particular challenges when looking into these alternatives. Click here for more information on all alternatives

Conventional (mass burn) incineration Click for further information

This option, which processes waste in a modern incinerator, has provoked quite a bit of discussion during our conversations.

The incinerators typically burn 250,000 tonnes or more of waste per year, and generate energy for heat or power. The Southern Landfill currently only receives about 75,000 of suitable waste per year which could create challenges with a higher relative cost of managing emissions and running the plant.

Issues and costs relate to the amount of waste required possibly impacting waste minimisation measures, the disposal of residual ash, managing emissions, and the disposal of unsuitable materials.

There are no current examples in New Zealand although a plant has been proposed for Hokitika. These methods are common in Asia, Europe, the UK and North America – all using large-scale incinerators.

Advanced thermal treatment Click for further information

This covers a range of technologies including pyrolysis and gasification to achieve thermal conversion of organic materials. Depending on conditions useable outputs include energy, Syngas, Tar/Oil for further refining and others.

Issues and costs relate to pre-sorting the waste, disposal of ash residue, managing emissions and the disposal of unsuitable materials.

There are no examples in New Zealand although trials have been completed for single waste streams (e.g. waste timber) but not general waste. These methods are used in the rest of the world but mostly for specific waste streams (e.g. tyres or wood waste).

Mechanical heat treatment Click for further information

Mechanical heat treatment combines mechanical sorting and heat treatment technologies to maximise the recovery of recyclable, usable material from general waste and processing the remaining waste.

Issues and costs relate to pre-sorting the waste, removal and disposal of recyclable, usable material, costs of disposing of unsuitable materials, and disposing of the output including low quality recyclable material, and stabilised organic material.

There are no examples in operation in New Zealand. There are examples in Australia but the final product is currently landfilled due to environmental regulations in some states. This method is also used in the United Kingdom.

Mechanical biological treatment Click for further information

Mechanical biological treatment is a generic term for an integrated system comprising several mechanical and biological processes which might include removal of recyclable materials, biological reduction of the biodegradable portion using anaerobic digestion and/or aerobic composting.

Issues and costs relate to a material recovery facility to remove unsuitable materials and their disposal, costs of disposing of the output including low quality recyclable material, and stabilised organic material.

There are no examples in operation in New Zealand. These methods are used in Australia New South Wales, Queensland and Western Australia, but in some states the final product is landfilled due to environmental regulations. There are many examples elsewhere in the world – in particular in Europe.

Click here for more information on all these alternatives.

We’ve had lots of great questions coming in thick and fast from our open days, our Facebook event and this Let’s Talk page.

Hot topics include ecological impacts – with a focus on Ōwhiro Stream and the Taputeranga Marine Reserve, the capacity of the Landfill, wanting to know more about the alternative waste management technologies and how we’re assessing those, what we do with sewage sludge and waste minimisation (including green waste, recycling etc).

We’ll be going into more info on these hot topics here on Let’s Talk over the next few weeks. In the meantime if you didn’t attend the Facebook chat you can review the questions and answers here: https://www.facebook.com/events/2101121723528984/

Next steps

The survey on what values are important to you closes on Friday 11 October. Tell us what you want us to focus on during our assessment of the alternative technologies.

We will be collating all your feedback on the values and using that to help us do the assessment. Before the end of November, we will have the results on that to share with you.

We will be holding more community engagement on the design of the chosen technology in late November and early December.

The existing stage of the Landfill will be full in approximately four years.

• Our resource consent for the current stage of the Landfill expires in April 2026.

• The Southern Landfill is operating in Stage 3 of its development with the proposed extension (Stage 4) needed to provide an additional 2.5 million m³ of landfill.

We want to know what Wellingtonians value to help us assess the alternatives to landfill and how we manage the waste, sewage and contaminated material of our growing city in the future.

Any solution will include our current waste diversion initiatives and be flexible enough to do more of these in the future.

Currently the Southern Landfill

• diverts approximately 8,000 tonnes of waste from the Landfill each year

• funds kerbside recycling

• funds free recycling drop-off at the Southern Landfill

This means a total of almost 11,500 tonnes is diverted from waste each year. (See our article on the Southern Landfill for more information)

The Council thinks extending the Landfill is the best way forward but would like to test this assumption by looking at alternatives including:

• closing the Landfill and/or the Transfer station

• building a waste-to-energy plant

• using biological processes

• heat treatment

Looking forward, we believe that things will change, and if landfilling is still the most viable solution for now, we think it will only be an interim step towards a future without landfills.

The Southern Landfill is a Council-owned and operated landfill located at 201 Landfill Road off Happy Valley Road. The site was opened in 1974 and is currently in the third stage of a multi-stage development. It sits on land specifically set aside in the District Plan for landfilling, with around 100 years of filling space left.

The Southern Landfill is a critical part of the city’s public health and sanitation infrastructure, dealing with the city’s waste, sewage and disposal of contaminated material (e.g. asbestos) from developments. It also forms part of the city’s resilience network, providing an area under the direct control of the Council to dispose of large amounts of demolition waste in case of a possible natural disaster.

Surpluses from the Southern Landfill subsidise recycling collection services, green-waste diversion to produce compost, the Tip Shop and other waste-minimisation activities to the tune of $6 million dollars per annum. We would need to find other ways to pay for these services if the Landfill stopped operating.

Any solution we come up with will include our current waste-diversion initiatives and be flexible enough to do more of these in the future. Currently the Southern Landfill diverts approximately 8,000 tonnes of waste from the Landfill each year. This consists of:

· Green waste diverted to compost – approximately 5,800 tonnes a year

· Food waste diverted to compost – approximately 1,600 tonnes per year

· Scrap metal diversion – approximately 575 tonnes each year

· Salvaged material from the transfer station and voluntary drop-offs of material to the Tip Shop for resale – estimated at 250 tonnes per year.

The Landfill also funds kerbside recycling and a free recycling drop-off at the Southern Landfill. This diverts approximately 11,500 tonnes of recyclable material from waste each year.

The current stage of the Southern Landfill has only 4 years capacity remaining so we are looking into a range of alternatives.

We will be checking the alternatives against a set of values, including costs, environmental impacts, track records in similar locations to Wellington and the time required from decision to getting the technology fully up and running. Click here to find out more about the values we will be using.

Click here to read more detailed information about the alternatives.

· Closure of the existing Southern Landfill and transfer station, with waste being sent directly to other landfills

· Closure of the existing Southern Landfill and continued operation of the Southern Landfill transfer station, with waste transported to another landfill

· Extension of the existing Southern Landfill into the next stage

· Conventional (mass burn) incineration, including any pre-sorting required to make this option viable

· Advanced thermal treatment (gasification, pyrolysis), including any pre-sorting required to make this option viable

· Mechanical heat treatment combining mechanical sorting and heat treatment technologies to maximise recycling and reuse from general waste and processing the remainder

· Mechanical biological treatment an integrated system of several mechanical and biological processes run alongside a materials recovery facility to remove unsuitable materials

As the current stage of the Southern Landfill only has four years capacity remaining, we are looking at what we do with waste next. We think extending the Landfill is the best way forward, but we need to check out what alternatives are around for Wellington's waste and rubbish. Alternatives like closing the Landfill, building a waste-to-energy plant or using biological processes.

All alternatives will be checked against a set of values including environmental impact, costs, track records in similar locations to Wellington and the time taken from decision to getting the technology fully up and running.

We want to know what values are important to you to help us with our decision making.

Values

• Community impacts/values

• Traffic volumes.
• Dust, noise, litter, odour, visual impacts
• Cultural concerns.
• Community image.
• Resilience implications for Wellington City – ability to manage waste within the boundaries of Wellington City in an emergency.
• Impacts on public health.

• Environmental

• Impacts on the surrounding environment, including fauna (fish, birds, reptiles etc) and flora (plants, trees).
• Groundwater pollution risk.
• Carbon emissions.
• Recreational use of land upon completion.
• Residual risks upon Landfill closure.
• Risk of technology in a seismically active environment

• Technology risk

• Availability of experts and equipment to maintain, operate and fix equipment.
• Is the technology future-proof – risk of obsolescence?
• Refer to existing applications/examples at a similar scale.
• Scalability of the technology – can it be scaled up or down easily if waste quantities change?

• Financial

• Capital cost of option from decision to operation.
• Operational costs.
• Funding option.

• Legislative/Resource Management Act risks

• Relevant policy direction and political environment for process.
• Risk of securing consents.

• Product risks

• Products produced by the alternative (e.g. compost from a composting plant or electricity from a waste-to-energy plant)?
• How much product is produced as a proportion of the initial input tonnage?
• Are there established and enough markets for the final product and how will it be distributed? (e.g Would we produce so much compost that we just end up disposing of it in a landfill?)?
• What would the residual waste be and how do we manage this safely.