Programme-wide Emissions Reduction - A Sustainable Way Towards Sustainability!

Alex Medich (Beca Ltd)

A Victorian water utility, serving over 1 million residents, is currently undertaking a 50-year master planning project to outline their Sewer and Recycled Water Mass Balance Plan (SRWMBP). The plan explores management solutions for recycled water volumes to achieve EPA license compliance and meet the utility’s environmental commitments.

Under Victoria’s water plan, Water for Victoria, the water sector has committed to achieving net-zero emissions by 2035, becoming the first state in Australia to do so. The sector has also committed to sourcing 100% of its electricity needs from renewables by 2025. For this commitment, water utilities are required to reduce emissions as much as possible and offset the remaining amount. This water utility has taken the initiative to be proactive and factor in Whole of Life Carbon (WoLC) as a decision-making criterion for their master planning project.

For the 50-year master planning project, five different solution packages were developed and assessed for their embodied and operational carbon. Within each solution package, recycled water is transferred to a combination of end uses including existing discharge schemes, new irrigation schemes, and environmental flows. Each solution package requires different infrastructure upgrades to allow for these transfers including pipelines, pump stations, new treatment plant equipment, and bulk water storage.

The operational emissions were assessed using the 2019 Intergovernmental Panel on Climate Change (IPCC) methodology. Compared to the Australian Government's methodology, which is based on the 2006 IPCC methodology, this assessment provided a more defined scope of emissions and allowed for better comparison between the options.

The embodied emissions were assessed using a range of different methods. Where possible, quantities of materials and emissions factors and databases (AusLCI, EPDs) were used to estimate emissions. Following this, rate-based data was used alongside emissions factors. The highest uncertainty came from using proxy data and estimating emissions based on similar projects or processes.

In the assessment, the solution package estimated to have the lowest WoLC emissions focused on the use of recycled water for environmental flows. The emissions for this option were 220,000 tCO2-e lower than for the highest emitting solution package. In terms of offsetting, we would need to cover a land area of roughly 2000ha with trees for 50 years to sequester the difference in carbon emissions.

The main reasons for lower emissions were:
• Embodied - fewer pipelines and less bulk water storage due to the management of recycled water flow variations.
• Operational - lower N2O emissions due to reduced discharge emissions with increased quality of the recycled water.

This paper discusses the methodology and outcomes of the carbon assessment and provides practical guidance on the application of the methodologies for future studies. It highlights the scale and challenge of emissions reduction associated with the hard-to-abate sector that is wastewater treatment and the benefits of implementing emissions as a decision-making criterion at the early planning stages of projects. The paper also identifies potential emissions reduction opportunities that can be used within the wider sector.