Life-Cycle Energy Use and Greenhouse Gas Emissions Inventory for Water Treatment Systems

Given the rising concerns over scarce energy resources and global climate change, life-cycle inventories focusing on energy use and greenhouse gas (GHG) emissions were developed for the City of Toronto municipal water treatment system (WTS). Three processes within the facility use phase of the life cycle were considered: Chemical production, transportation of materials, and water treatment plant operation. The impacts of chemical manufacturing were estimated using the economic input-output life-cycle assessment model, while the inventories for transportation and operational environmental effects were based on data from the GHGenius model and regionally averaged data. Operational burdens, 60% of which are attributed to on-site pumping, accounted for 94% of total energy use and 90% of GHG emissions. By contrast, transportation-related energy use and emissions were deemed insignificant. The normalized energy use of the studied WTS was found to be between 2.3 and 2.5MJ∕m3 of water treated. Water conservation practices are recommended as abatement strategies for the energy use and GHG emissions associated with water treatment. The limitations and uncertainties introduced by selected model parameters and through combining various estimation methodologies are discussed, as is the model’s relevance.