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A Predictive Model of Greenhouse Gas Emissions from Urban Water Systems

Congress: 2008
Author(s): David J.M. Flower, V. Grace Mitchell & Gary P. Codner
Institute for Sustainable Water Resources & eWater CRC, Department of Civil Engineering, Monash University, Victoria, Australia

Keyword(s): Greenhouse Gas Emissions, Urban Water Systems, Energy Consumption, Climate Change
AbstractIntroduction According to the latest predictions, human induced climate change has the potential to significantly disrupt urban water systems in Australia as it manifests itself during the next century. The current set of challenges associated with providing urban communities with water related services will be exacerbated by the reduced availability of water from traditional sources, and increased demand for water (see, for example Howe et al. 2005, Preston & Jones 2006). The vulnerability of urban water systems to climate change has been widely recognised; but the contribution of urban water systems to climate change is less well understood. Significant urban water system greenhouse gas (GHG) emissions are associated with: (a) the consumption of energy harvested from carbon based fuels, (b) anaerobic wastewater treatment processes, and (c) the consumption of goods and services that involved energy input or the direct generation of greenhouse gases at some upstream point. Objective The aim of this research project is to quantify the GHG emissions associated with urban water systems, and to determine the most effective pathways to reducing those emissions. The purpose of this paper in particular is to communicate the findings of this research project, with a particular focus on scaling the water-related GHG emissions of a single household up to citywide water-related GHG emissions. Methodology/Results In this project, the system boundary has been drawn such that the operational GHG emissions associated with: (a) water supply systems, (b) the residential end uses of water, and (c) wastewater systems have been quantified. It will be shown that the total GHG emissions associated with urban water systems are subject to considerable spatial and temporal variability, with over 80 governing parameters required to determine such emissions for a particular household in a specific location, each of which can fall within a very broad range of values. This paper will address this issue in detail, using Melbourne, Australia as the case study urban water system. Frequency distributions of GHG emissions for each residential end use of water in Melbourne will be presented, and strategies aimed at minimising those GHG emissions will be proposed. Conclusions It will be revealed that the GHG emissions associated with the major fraction of urban water systems associated with servicing residential consumers are strongly and consistently dominated by those intrinsic to the end uses of water, especially those associated with heating water for showering. The most effective pathway to reducing the GHG emissions associated with the Melbourne urban water system is to reduce those associated specifically with heating water. This can be achieved by either reducing the volume of water heated, or changing the fuels or processes employed for this purpose. It will be shown that this conclusion is generally valid in an international context, although this requires reassessment on a case by case basis. References Howe, C., Jones, R.N., Maheepala, S. & Rhodes, B. 2005. Melbourne Water Climate Change Study - Implications of Potential Climate Change for Melbourne's Water Resources. CSIRO Urban Water and Climate Impact Groups & Melbourne Water. Melbourne, Australia. Preston, B.L. & Jones, R.N. 2006. Climate Change Impacts on Australia and the Benefits of Early Action to Reduce Global Greenhouse Gas Emissions. CSIRO Marine and Atmospheric Research. Melbourne, Australia.
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