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Sustainable choices for residential water supply in Auckland

This outline discusses sustainable water supply choices for residential areas in Auckland, including mains supply vs. rain tanks, settlement patterns impact, life cycle analysis, energy consumption, and CO2 emissions.

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Sustainable choices for residential water supply in Auckland

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  1. Sustainable choices for residential water supply in Auckland Nalanie Mithraratne & Robert Vale Centre for Urban Ecosystem Sustainability Landcare Research

  2. Outline • Mains supply vs. rain tanks • Impact of settlement patterns • Water system in average house • Conclusions

  3. LCA of mains supply • System boundary • Initial construction • Maintenance/ replacements - 1% of the total length of pipes/year replaced • Operational requirements • Analysis period – 100 years

  4. Bulk supply system - constructionLIFE CYCLE ENERGY

  5. Bulk supply system LCE LCCO2

  6. Local supply network - 2005 • CLS - cement lined steel • CI - cast iron • PE - polyethylene • AC - asbestos cement

  7. Mains supply performance • Energy intensity = 2.11MJ/m3(Range 2.08 - 2.27MJ/m3) • CO2 emissions factor = 0.128kgCO2/m3(Range 0.126 – 0.146kgCO2/m3) Mains water supply contribution, • Life cycle energy = 86GJ/house • CO2 emissions = 4.9 tonnes CO2/house

  8. Impact of Settlement Pattern Roberton site • Residential density 14units/ha • Parallelogram bounded by roads

  9. Impact of Settlement Pattern Sandringham site • Residential density 17units/ha • Road across the site

  10. Impact of Settlement Pattern Freeman’s Bay site • Residential density 23units/ha • Trapezoid, open spaces within

  11. Impact of Settlement Pattern Ponsonby site • Residential density 24units/ha • Rectangle bounded by roads

  12. Life Cycle Energy and LCCO2 (actual)

  13. Life Cycle Energy composition

  14. Life Cycle CO2 composition

  15. Mains supply vs. Rain tanks • Wastewater and stormwater • Mains - more, rain tanks - reduced • Water quality • Mains - Grade A, rain tanks – untreated • Water supply volume • Mains - 370m3, rain tanks - varies

  16. House size and rain water volume

  17. Rain harvesting system [Source: Marley 2005]

  18. Water supply systems - LCELIFE CYCLE ENERGY (GJ)

  19. Water supply systems – LCCO2LIFE CYCLE CO2 (kg)

  20. Water supply systems – LCCLIFE CYCLE COST (NZ$)

  21. Building Industry Advisory Council House (BIAC) Plan [Source: Baird and Chan (1983)]

  22. Building Industry Advisory Council House (BIAC) Section & Front Elevation [Source: Baird and Chan (1983)]

  23. ASSUMPTIONS • Useful life of NZ houses is 100 years. • Living room faces north. • Space heating: Whole house, temp 18oC, 2 schedules • Water heating: varies with water volume.

  24. Life cycle energy by end use

  25. Life cycle CO2 by end use

  26. Life cycle cost by end use

  27. Conclusions • Consumption significantly impacts the system choice. • Use of mains supply in smaller houses (>150m2) and rain harvesting in larger houses is better for the environment. • Mains supply is cheaper initially but costly in life cycle terms. • Water supply is negligible in terms of total environmental performance of house.

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