A metabolism perspective on alternative urban water servicing options using water mass balance

Urban areas will need to pursue new water servicing options to ensure local supply security. Decisions about how best to employ them are not straightforward due to multiple considerations and the potential for problem shifting among them. We hypothesise that urban water metabolism evaluation based a water mass balance can help address this, and explore the utility of this perspective and the new insights it provides about water servicing options. Using a water mass balance evaluation framework, which considers direct urban water flows (both ‘natural’ hydrological and ‘anthropogenic’ flows), as well as water-related energy, we evaluated how the use of alternative water sources (stormwater/rainwater harvesting, wastewater/greywater recycling) at different scales influences the ‘local water metabolism’ of a case study urban development. New indicators were devised to represent the water-related ‘resource efficiency’ and ‘hydrological performance’ of the urban area. The new insights gained were the extent to which alternative water supplies influence the water efficiency and hydrological performance of the urban area, and the potential energy trade-offs. The novel contribution is the development of new indicators of urban water resource performance that bring together considerations of both the ‘anthropogenic’ and ‘natural’ water cycles, and the interactions between them. These are used for the first time to test alternative water servicing scenarios, and to provide a new perspective to complement broader sustainability assessments of urban water

An inclusive city water account by integrating multiple data sources for South-East Queensland (SEQ), Australia

Cities are the hotspots of impacts on local and distant water resources through economic activity and consumption. More than half of the world's population lives in cities, which is expected to reach around two-thirds by 2050. Such a high level of increased urbanization calls for higher attention towards inclusive, safe, resilient, and sustainable cities (Sustainable Development Goals 11). To evaluate sustainability, inclusiveness, and resiliency pathways, a variety of sustainability indicators have been proposed, including the water footprint. The water footprint is defined as the total volume of freshwater used for the goods and services consumed. It covers both direct (e.g. drinking and cleaning) and virtual water flows (water used in the goods and services supply chain, hence also known as embedded water). Virtual water flows through products and services produced in other locations using their water resources influence the function, prosperity, and growth of the cities. Yet, this aspect is absent in the sustainability and strategic city water footprint reduction goals of Australian cities. To fully account for the water dependencies of Australian cities, direct and virtual water flows need to be known. To this purpose, we build inclusive city water of South-East Queensland (SEQ) by combining material flow analysis (MFA) and the multiregional input-output (MRIO) model. Water consumption in SEQ is used to quantify the water footprint on local water resources and net blue virtual water import. Together, this constitutes the water footprint on national water resources. Our results show that the water footprint of SEQ on local water resources is 620 GL with a net virtual water import of 1382 GL. Therefore, the water footprint of SEQ on national water resources is 2002 GL. The water footprint of SEQ on local water resources consists of direct water consumption by households (192 GL) and the industrial sector (428 GL). The consumed direct water of the SEQ industrial sector flows as virtual water to SEQ (149 GL), the rest of Australia (RoAUS) (all other regions except SEQ) (211 GL), and the rest of the world (68 GL). The virtual water inflows breakdown by source regions showed that 386 GL, 1019 GL, and 256 GL of virtual water imported from the major cities (Sydney, Melbourne, Adelaide, and Perth); regional areas of NSW, Victoria, and QLD; and RoAUS, respectively. Overall, the proposed inclusive city water account can enhance subnational estimates of city water footprint for benchmarking, as well as inclusive and resilient city water planning

Evaluation approaches for advancing urban water goals

Urban areas (especially cities) are challenged in meeting their direct water needs from local sources. They also exert strain on global water resources through their indirect (virtual) water use. Agencies concerned with urban water management have visions and goals for managing direct water use, but indirect use is only inferred in more global visions for sustainable consumption. There is limited quantification of "urban water performance" at the macro urban scale (whole of city) to monitor progress toward these goals. It is constrained by a lack of clarity about the evaluation approaches that best serve them. We ask, How can the evaluation approaches described in literature advance urban water management goals? We reviewed the utility of eight evaluation approaches, including urban water system modeling, urban metabolism (territorial and mass balance), consumption (life cycle assessment, water footprinting, and input-output analysis), and complex systems (ecological network analysis and systems dynamics) approaches. We found that urban metabolism based on water mass balance is a core method for generating information to inform current goals for direct urban water use, with potential for being "coupled" with the other approaches. Consumption approaches inform the management of indirect water use. We describe this in a framework for urban water evaluation to give greater clarity to this field and flag the further research that would be needed to progress this. It includes the recommendation to differentiate the evaluation of direct and indirect urban water, but to also interpret them together

Life cycle assessment of Australian sugarcane products with a focus on cane processing

Purpose This work generates attributional life cycle assessment (LCA) results for products produced from Australian sugarcane-raw sugar, molasses, electricity (from bagasse combustion), and ethanol (from molasses). It focuses on cane processing in sugar mills and is a companion to the work presented in (Renouf et al. 2010), where the focus is on cane growing. This work also examines the preferred approach for assigning impacts to the multiple products from cane processing, and the influence that variability in cane growing has on the results

Bio-production from Australian sugarcane: An environmental investigation of product diversification in an agro-industry

This paper assesses the environmental impacts of producing bio-energy, bio-fuels and bio-materials from Australian sugarcane (Saccharum officinarum), and nominates the bio-production pathways offering the best environmental gains. A system-based, consequential approach was taken, which is different to past approaches that have commonly judged bio-production by comparing individual bio-products with their fossil-fuel counterparts. Possible diversified scenarios were developed, and the changes in environmental impacts from the system as a whole (per 100 t sugarcane processed) were assessed using life cycle assessment (LCA). Scenarios based on utilisation of co-products from existing sugarcane production (ethanol from molasses, and electricity and ethanol from surplus bagasse) were found to give modest reductions in non-renewable energy (NRE) use and global warming potential (GWP), and involve no or few trade-offs. Of these, ethanol and electricity from bagasse offer the best benefits. Scenarios necessitating expanded cane growing for dedicated production of ethanol and polylactide (PLA) plastics from cane juice were found to result in more substantial NRE and GWP savings, but involve the trade-offs associated with expanded agricultural production (land use, water use and potential water quality impacts). Of these, PLA production offers the better outcomes, amongst the scenarios. However, eco-efficient cane growing was found to be an equally important improvement strategy and should be implemented to enhance the benefits and mitigate some of the trade-off from bio-production.</p

Integrated urban water systems

Water plays a central role in creating sustainable cities. Past focus has been on centralised potable water supplies, wastewater treatment and drainage. However, focus is shifting towards localised fit-for purpose supplies, restoring natural water flows, minimising water-related energy, and achieving liveability through water. New conceptual frameworks help us understand this broader context. The urban water metabolism framework gives a big-picture perspective and comprehensive account of all water flows to generate water performance indicators. Quantification of the energy- and carbon-intensity of urban water (life cycle assessment and marginal abatement cost curves) helps identify the role of water management in decarbonising cities. Frameworks for understanding water-related liveability help us consider water efficiency in terms of the broader functions water delivers, instead of just per unit supplied