Setting Wellington Water on a Pathway to Net Zero Emissions

S Friggens, Technical Director Carbon & Climate (Mott MacDonald)

A Temple, Principal Process Engineer (Mott MacDonald)

N Dempsey, Technical Director Water (Mott MacDonald)

U Dele, Chief Advisor Stormwater & Climate (Wellington Water)

F Clark, Head of Strategy (Wellington Water)

Y Praveen, Carbon Modeller (Wellington Water)

The water sector is responsible for 5% of global Greenhouse Gas emissions (Thacker et al. 2021), and these emissions must be rapidly reduced over the coming decades if we are to achieve national and global climate change targets. The challenge for the water sector is profound. Emissions result from a wide variety of activities including carbon intensive infrastructure build, energy and chemical use over the operational lifetime of water and wastewater processes, and substantial amounts of biogenic methane and nitrous oxide from wastewater treatment and sludge disposal. An ambitious, planned, collaborative and holistic approach is needed to transition the sector to net zero by 2050.

Wellington Water is committed to playing a leading role in reducing its ownemissions and influencing others in the industry to do the same. This paper outlines analysis undertaken by Wellington Water and Mott MacDonald that explores options and pathways to reduce Wellington Water’s operational emissions. In line with best practice science-based approaches, reductions of at least 50% by 2030 and net zero by 2050 are explored. This paper shows that such an ambitious pathway is possible but requires immediate action with a particular focus on key emissions hot spots. It proposes a framework of next steps to achieve these aspirations, including the implementation of low-regrets measures now whilst a longer-term integrated net zero plan is developed; embedding whole-life emissions reduction into governance, leadership and decision making; and engaging externally to shape emerging Water Reforms.

The work outlined in this paper is a first for the water sector in New Zealand and draws on international learning from the UK and elsewhere. Multiple emissions  pathways are analysed: A Business-As-Usual pathway shows emissions increasing overtime due to population growth; a Moderate Ambition Pathway achieves substantial but insufficient emissions cuts, and a Step-Change Pathway that reduces emissions by almost 90% by 2050 representing a near best case scenario where financial and policy barriers are removed, investment increased and significant technology changes are achieved. 

The paper identifies specific opportunities for Wellington Water to reduce wastewater treatment and effluent discharge emissions, reduce then eliminate sludge disposal emissions, eliminate the use of fossil fuel energy and reduce the use and embodied carbon of treatment chemicals. The analysis serves as a model for water companies around New Zealand who wish to embark on a similarly ambitious journey. It can act as a call-to-arms for the water sector to commit to action to help preserve a habitable climate for future life on Earth.