Hamilton City Council is leading the way when it comes to calculating the carbon emissions generated by wastewater treatment.

Since 2019, Council has been working with engineering consultancy Beca to model the carbon footprint and energy use at the Pukete Wastewater Treatment Plant.

The work is part of Council’s organisation-wide drive to understand its carbon emissions so that opportunities to reduce those can be identified and implemented.

To calculate the wastewater treatment plant’s emissions, a number of industry standards, practises, and assumptions were used, including international guidelines from the Intergovernmental Panel on Climate Change and United Nations Framework Convention on Climate Change.

This led to Council pioneering the development of standalone New Zealand guidelines for the calculation of emissions associated with wastewater treatment.

It has also triggered further ground-breaking research to verify the international guidelines used as part of the new national specification are relevant to New Zealand.

Infrastructure Operations General Manager Eeva-Liisa Wright said the collaboration with Beca will produce great outcomes not just for Hamilton but across New Zealand.

“The main priority for this work is to be able to find ways for us to cut our carbon emissions and energy use, so that we can achieve our own climate change targets and comply with the Zero Carbon Bill. Being recognised nationally for what we’ve done is just a cherry on top.

“The wastewater treatment process is Council’s largest source of greenhouse gas (GHG) emissions and biggest consumer of electricity and natural gas. Whatever we can do to optimise the plant’s performance will make a valuable contribution to Council and our city being more sustainable.”

The model has already calculated that an upgrade to the plant’s blowers, currently underway, will increase site electricity efficiency by around 16%, saving Council almost 1.5 million kWh per year – that’s equal to the average annual electricity use of 113 households!

Council and Beca presented the findings of the carbon and energy assessment to the Water New Zealand Conference at Claudelands Events Centre last week and are continuing to work with the industry group to develop the new national guidelines.

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