Making wastewater decarbonisation real for New Zealand

There are good local and overseas examples where decarbonisation has been integrated into long-term water and wastewater asset planning.

One example is GHD’s involvement in developing and implementing York Region’s carbon management study in Ontario, Canada. York Region, one of North America’s fastest growing areas, serves a population of over a million and operates a range of water and wastewater assets similar to those in New Zealand¹. The framework has built-in flexibility to accommodate different sizes and types of water and wastewater projects undertaken by the York Region staff, design consultants and contractors. Its key features include clearly documenting baseline and alternative scenarios to achieve greenhouse gas reductions, along with outlining the underlying assumptions and cost estimates. This incorporates greenhouse gas reduction across the whole asset life cycle, from planning and design to capital delivery, in a repeatable and consistent way.

The framework is designed to drive a shift in mindset and culture among staff and contractors in the York Region, embedding greenhouse gas reduction into everyday operations. It’s an approach that our water services providers need to seriously consider as they navigate this time of change.

Engineering decisions are inherently complex, often requiring trade-offs between different and conflicting drivers. Historically, reducing energy consumption and maximising energy recovery have been key focusses in driving sustainability in wastewater treatment, and they remain the most common decarbonisation strategies. However, as New Zealand’s electricity grid continues to decarbonise, these drivers alone may not suffice. A 2018 comparative study by Dr David de Haas, GHD Senior Wastewater Technical Director, revealed that the plant configurations with the highest energy self-sufficient potential could also carry a higher risk of greenhouse gas process emissions. 

Decarbonisation is often seen as a daunting challenge, but how we operate our water and wastewater assets is key to addressing emissions in the sector, increasing our chances of achieving net zero by 2050.

An example is a project GHD undertook almost a decade ago, optimising a 750,000 PE wastewater treatment plant by working closely with plant operators. This not only restored the plant’s capacity and avoided a costly upgrade but also reduced its fugitive emissions and improved biogas production for energy recovery.

Having more people within the water sector with diverse technical backgrounds engaged in the decarbonisation journey is essential, as this will likely lead to higher adoption of newer tools such as machine learning and emerging technology solutions. GHD is currently involved in several process emission monitoring and mitigation projects, applying advanced process control techniques, including model predictive control and machine learning, to generate insights. These insights aim to identify nitrous oxide emission mitigation measures not just for the study sites, but with broader implications for the water sector.

Time is running out to meet the 2050 net zero goal. Emission reductions in the water sector will be part of the decarbonisation puzzle, alongside major initiatives in other sectors such as transport and energy.

New Zealand is uniquely positioned with the perspective of Te Ao Māori, which embraces the intertwined nature and interdependence of humans and the environment². Key principles of kaitiakitanga (guardianship), mātauranga (knowledge) and manaakitanga (hospitality and respect) provide a strong foundation for adopting holistic thinking, particularly with its strong affinity for nature-based solutions over traditional grey infrastructure.

While short-term drivers can distract from realising these long-term opportunities towards a decarbonised future, we must keep making progress, continue learning and share the message of the water sector decarbonisation with our communities.

¹ Jeremy Kraemer’s 2024 IWA Conference Paper: Integrating GHG Evaluation and Reduction into Water and Wastewater Infrastructure Capital Delivery
²  Weaving Te Ao Māori into climate action