Cutting carbon on water infrastructure planning in New Zealand

Water infrastructure and climate change 

The water sector is responsible for around 5% of global greenhouse gas emissions, according to the UN. These come from both the construction and operation of its infrastructure assets and from the treatment process itself – for example, biogenic methane. In New Zealand, Water New Zealand has developed guidance for reducing these emissions.

Wellington Water is responsible for managing the drinking water supply, wastewater and stormwater assets in the Wellington region of New Zealand. Faced with aging infrastructure and population growth, it must invest to improve water quality and meet increased demand – while reducing its emissions to net zero by 2050.

In planning its programme of works for the coming decades, the water operator sought to embed emissions reductions and whole life carbon considerations into infrastructure delivery, in line with New Zealand’s Carbon Zero Act. To do so required first a thorough analysis of its current carbon position – and that’s where we stepped in.

Frameworks for net zero 

Wellington Water operates in the context of various legislative and advisory frameworks that set out guidance on achieving net zero emissions:

National

In the Climate Change Response Act 2002, New Zealand established a legal framework for how it will meet its international obligations under the UN Framework Convention on Climate Change and the Paris Agreement. This legislation sets out New Zealand’s emissions reduction targets, including net zero ‘long-lived’ greenhouse gases by 2050.

Regional

The Wellington region has formulated an emissions reduction plan that sets out a strategic approach to transitioning the Wellington–Wairarapa–Horowhenua region to zero carbon, while meeting the needs of the community.

Sector

The Navigating to Net Zero report was developed by Water New Zealand’s climate group to help guide water service providers on the journey to a low carbon future. It provides a starting point and sets out how the water industry can plan to reduce carbon emissions to achieve a net zero target.

Analysing Wellington Water’s emissions

The main sources of Wellington Water’s emissions include infrastructure construction, biogenic methane and nitrous oxide from wastewater treatment and sludge disposal, chemical use for water treatment, and fossil fuel use. 
The company’s aspiration is to reduce all of these in line with its climate change objectives – but to do so, it needed to get a more detailed picture of present and predicted emissions and the options for change.

89 planned water projects analysed for predicted emissions

Setting a capital carbon baseline

As a starting point, we analysed the emissions associated with infrastructure construction and renewals projects between 2021 and 2024 so that this data could serve as a baseline for future emissions reductions.

We engaged with project managers to model the baseline emissions of around 90 planned drinking water, wastewater and stormwater projects, representing roughly 80% of planned capital spend. We used the Moata Carbon Portal to analyse bills of quantities and draw on industry benchmarks in order to estimate the emissions from materials, transport and construction work for these projects.

Moata Carbon Portal is a digital solution aligned with PAS 2080 principles that allows anyone in an organisation and throughout the supply chain to easily identify and calculate carbon emissions on infrastructure projects.

Wellington Water is using this tool to assess and report emissions as part of its capital delivery process and to evaluate potential lower carbon solutions.

In a baseline scenario, we found that around 68,800 tonnes of carbon dioxide (tCO2e) would likely be emitted through the construction and renewals planned, mainly from drinking water assets. Most of that would be associated with materials, as water infrastructure projects use vast amounts of concrete, steel pipes, steel reinforcement and aluminium.

Pipe and manhole assets, largely associated with the network projects, make up a third of the total embodied carbon. Reservoirs also account for a large proportion, because of the number of storage projects planned by Wellington Water to address water quality and supply shortfalls.

This work is now informing Wellington Water’s decarbonisation efforts and was a key factor in a review of its capital delivery process to incorporate carbon into decision making. The organisation is now exploring opportunities to reduce the need for new infrastructure and, where construction is essential, identify lower carbon alternatives as construction materials.

Taking an operational emissions inventory

Wellington Water also wanted to understand the operational emissions of its existing infrastructure assets and its head office and management functions, to inform future carbon reduction efforts.

We applied the principles of the GHG Protocol Corporate Accounting and Reporting Standard to develop a sophisticated estimate of Wellington Water’s current operational emissions. The process involved considering recent updates to established methodologies for measuring biogenic emissions in wastewater treatment processes. We worked with Wellington Water to collect activity data for a range of activities and used this to estimate its emissions.

Based on the company’s 2020/21 inventory, its total operational emissions amounted to 48,438tCO2e. This was subsequently broken down by scope, activity and client council. We found that over 60% of Wellington Water’s operational emissions are biogenic, mainly from wastewater treatment, effluent discharge and sludge disposal. Knowing this has enabled the water operator to make informed decisions on where to focus its carbon cutting efforts.

60% of operational emissions are biogenic, mainly from wastewater treatment, effluent discharge and sludge disposal

Wellington Water’s objectives

• Minimise operational and capital carbon emissions
• Consider whole life carbon, including through no-build solutions
• Prioritise emission reductions over offsets
• Be low-energy and, where practicable, own-energy
• Understand and be resilient to climate change impacts
• Adapt to climate change together with communities and councils

Identifying options to reduce emissions

Carbon reduction pathways

Wellington Water emits over 48,000 tCO2e each year from the operation of its assets. To meet its net zero objective, these emissions must be reduced rapidly over the next few decades. But what does a pathway to net zero by 2050 look like, and what are the key steps to achieving this goal?

Working with Wellington Water, we analysed the options for reducing its operational emissions. We demonstrated that an ambitious net zero pathway is possible – even in the face of anticipated population growth – but requires immediate action, with a focus on emissions hot spots.

We identified specific opportunities for Wellington Water to reduce wastewater treatment and effluent discharge emissions, eliminate sludge disposal emissions, stop using fossil fuel energy, and minimise embodied carbon from treatment chemicals.

“As part of the study, we compared three carbon reduction pathways each using the 2020-21 inventory as a baseline: business-as-usual, moderate effort and step-change,” says Sam Friggens, technical director, energy advisory and climate change at Mott MacDonald. “In a step-change scenario, gross emissions both from biogenic methane and long-lived GHGs can be reduced by more than 50% by 2030 and almost 90% by 2050, aligning with Paris Agreement temperature goals.”

A framework was then developed for the next steps to achieve these aims. This includes implementing now the measures least likely to bring later regret, as well as formulating a longer-term net zero plan. In addition, it sets out how Wellington Water can embed whole life carbon reduction into its own governance and decision making, while engaging externally to influence New Zealand’s emerging water reforms.

This net zero pathway is being used to inform Wellington Water’s near-term decarbonisation actions as well as its longer-term investment decisions. The roadmap also enables it to recommend effective carbon reduction steps to its client councils. What’s more, the analysis we have undertaken for Wellington Water serves as a model for other water companies around New Zealand.

Sam Friggens reiterated that “achieving the level of carbon reduction required is unlikely to be possible without concerted coordinated effort across industry and government, and Wellington Water is leading the way.”

48,428t total operational emissions in 2020/21

90% reduction in operational emissions by 2050

A holistic view of the 2050 roadmap

Wellington Water needed visibility of its capital works across six councils to effectively manage carbon across the project lifecycle at a programme level. Visualising its Scope 3 emissions in the context of its organisational inventory has allowed the organisation to focus efforts and track progress towards its net zero target.

Having developed their 2050 roadmap, we created a single digital dashboard to display the various pathways and interventions against each emission category. We then overlaid this with known Scope 3 emissions from Wellington Water’s capital works to provide the first holistic view of its greenhouse gas inventory.

“Digitising Wellington Water’s inventory and roadmap into a dashboard means it now has a breadcrumb trail for the next thirty years. It can plan the interventions required to decarbonise its operations and construction works and analyse how it is progressing against its near- and long-term targets,” says Jonny Breen, principal digital consultant at Mott MacDonald.

Embedding carbon into infrastructure decision making

Capital project delivery process and carbon guidance

Wellington Water wanted to improve its capital project delivery processes to ensure a consistent way of planning and executing projects, while delivering broader outcomes such as carbon reduction in line with its overall company objectives.

We reviewed the delivery processes used by different parts of the business and worked with stakeholders – within Wellington Water, the consultant panel and the contractor panel – to develop a consistent project lifecycle and governance framework. We reviewed the templates required for delivering various types of capital projects across the business ensuring that correct information was provided at each gateway to enable an informed decision about project progress. We created a new SharePoint site accessible to Wellington Water, the consultant panel and the contractor panel, to provide access to all templates, guidance documents, policies and procedures required for capital project delivery.

“Having a consistent project lifecycle and governance framework for delivering capital projects was especially important for the consultant panel who deliver 90% of the projects within Wellington Water but have limited access to the intranet site it was currently using,” says Victoria Day, technical director, advisory at Mott MacDonald. “The capital project delivery process isn’t a static framework either, improvements will continue to be implemented based on the ongoing feedback received.”

Regular carbon gateway reviews are now integrated into project delivery. We have prepared guidance for project managers to measure and reduce carbon at every stage, from early strategy and concept through to detailed design, procurement and construction. We have also delivered support, training and a handbook to project managers and engineers on using the Moata Carbon Portal tool to measure emissions.

Wellington Water now has a clear capital project delivery process and governance framework, with carbon management built in. The process is understood by all stakeholders, enabling project teams to focus on delivery. This approach to carbon reflects PAS 2080 best practice principles, including the carbon reduction hierarchy (avoid – switch – improve), the creation of a baseline, and the need to measure and report carbon at every stage. Over time this will evolve from capital to whole life carbon and benefit from a process of continual learning.

Applying the net zero pathway in practice

Wellington Water is already applying the methods and principles of its new net zero pathway to projects in the pipeline. Thanks to our analysis and modelling, the company is now leading the way by demonstrating its commitment to reducing emissions through various practical initiatives.

Regional biosolids strategy

Sludge management is a significant contributor to operational carbon emissions for wastewater treatment in the Wellington region. As the growing amounts of sludge must be mixed with general waste, waste minimisation becomes increasingly hard. This has been identified as a focus for Wellington Water’s roadmap to net zero.

We are working on a regional biosolids strategy with the water company and its key stakeholders to tackle this key inhibitor to the region’s waste minimisation and net zero aspirations. This includes exploring sustainable end-use options that create value from biosolids, thereby reducing waste to landfill and the emissions from management and disposal.

Moa Point Sludge Minimisation facility

More than a million litres of sludge are piped from the Moa Point wastewater treatment plant to a sludge dewatering plant at the Southern Landfill every day. Once most of the water has been removed, this leaves roughly 45 tonnes of solids to be buried in the landfill. Methane, which is 25 times as potent as carbon dioxide, is emitted during this process, contributing heavily to the facility’s carbon footprint.

Wellington Water has investigated alternate sewage sludge disposal technologies to achieve waste and carbon reduction targets, and we have been helping Wellington City Council and the Crown Infrastructure Partnership secure funding for this by assessing the potential emissions reductions. Wellington Water continues to provide technical support for the project and will ultimately be responsible for its operation.

Seaview sludge dryer

Our net zero pathway work for Wellington Water highlighted the need to eliminate use of natural gas, a major contributor to operational carbon emissions. This insight has led the company to one of its biggest opportunities for emissions savings. The existing natural dryer is reaching its end of life and is scheduled to be replaced. The new dryer will be designed to use a renewable energy source, with investigations into the design now under way.

Wellesley College stream remediation

A stream flowing alongside Wellesley College that forms an essential part of the local stormwater network was eroding. Standard practice would be to build carbon intensive retaining walls to mitigate the erosion. We worked with Wellington Water to explore low carbon alternatives to remediate the stream.

Our solution was to use in-stream structures, such as cascades and cross vanes, to slow the flow of the water and dissipate its energy. This allowed us to minimise reliance on retaining walls to selected spots where essential to protect the school’s infrastructure. This low carbon approach, preserving the stream’s natural feel, has also yielded better outcomes for the environment. These include improving fish passage, creating habitat pools and encouraging regeneration of native vegetation along the banks.

Collaborating with industry

Accelerating decarbonisation and transitioning to net zero requires collaboration and collective action across supply chains. Recognising the urgent need to address climate change, Wellington Water is supporting discussions on emissions reduction at both a local and regional level.

A Carbon Community Group has been convened, bringing together Wellington Water’s consultant and contractor panels to work collaboratively to deliver low carbon outcomes in capital project delivery. The group provides a platform for Wellington Water’s delivery value chain to share carbon initiatives, workshop solutions and share knowledge, learnings, success stories and resources to keep the carbon dialogue front of mind.