Intergrating Water Use and Water Quality into Environmental Life Cycle Assessment: Limitations and Advancements Derived from Applications

Incorporating water use and water quality pollution impacts in life cycle assessment (LCA) methods is of great value for better management of water resources. Considerable research and impact assessment methods for water LCA have been developed. However, no consensus has been reached and water impacts are not treated consistently in LCA at present. In this dissertation, I have developed a water LCA approach, which assesses the impacts of water use and water quality pollution in an integrated way. In this approach, consumptive water use and nonconsumptive water use are separately assessed. Consumptive water use refers to freshwater that is extracted from a resource and used in such a way that it is not released back to the original watershed. Non-consumptive water use is water returned to the original watershed that may be used again. Consumptive water use might cause direct impacts on water quantity, while non-consumptive water use might result in direct impacts on water quality pollution. In the present work, environmental impacts on water resources and aquatic environments are estimated by applying relevant impact characterization factors to water consumption and pollutant emissions. In addition, cost of the wastewater treatment method selected is proposed as an impact indicator for water quality pollution.;Three examples were used to demonstrate the application of this approach: 1) coal-fired electricity power generation; 2) Marcellus shale gas wells; 3) concrete manufacturing with cement and several cement substitutes. The example of coalfired electricity power generation showed that, on average, 1.2 cubic meters of freshwater are consumed per MWh of electricity generated, which could be primarily attributed to the cooling process. As for the water quality pollution, impacts from coal mining and electricity generation are comparable and influenced greatly by wastewater treatment. The case study of Marcellus shale gas wells showed that 0.005 to 0.02 liters of freshwater is consumed per MJ of gas produced, excluding utilization of gas at end use. Most of the potential water quality pollution impacts are associated with produced water from gas development. The case study of concrete with cement and cement substitutes showed that 8 to 14 cubic meters of freshwater withdrawal are required per cubic meter of conventional concrete with compressive strength of 20 to 35 MPa. Replacing cement with cement substitutes, glass powder and alkaline activated slag, in concrete could reduce its life cycle water withdrawal and impacts of water quality pollution.;These three case studies demonstrate that a life cycle perspective can improve the understanding of water sustainability issues. For coal fired electricity generation and Marcellus shale gas development, direct water use for onsite operations have higher impacts than water use for supply chain production across their life cycle. In contrast, for concrete with cement and cement substitutes, indirect water use has much higher impacts than direct water use at production facilities.;In addition, the application of this water LCA approach to industrial products enables the consideration of water impacts as a specific category and the comparison of water impacts with other environmental impacts. In this dissertation, life cycle greenhouse gas (GHG) emissions of the three products were estimated.