Energy and Air Emission Effects of Water Supply

Abstract

Life-cycle air emission effects of supplying water are explored using a hybrid life-cycle assessment. For the typically sized U.S. utility analyzed, recycled water is preferable to desalination and comparable to importation. Seawater desalination has an energy and air emission footprint that is 1.5-2.4 times larger than that of imported water. However, some desalination modes fare better; brackish groundwater is 53-66% as environmentally intensive as seawater desalination. The annual water needs (326 m 3 ) of a typical Californian that is met with imported water requires 5.8 GJ of energy and creates 360 kg of CO 2 equivalent emissions. With seawater desalination, energy use would increase to 14 GJ and 800 kg of CO 2 equivalent emissions. Meeting the water demand of California with desalination would consume 52% of the state's electricity. Supply options were reassessed using alternative electricity mixes, including the average mix of the United States and several renewable sources. Desalination using solar thermal energy has lower greenhouse gas emissions than that of imported and recycled water (using California's electricity mix), but using the U.S. mix increases the environmental footprint by 1.5 times. A comparison with a more energy-intensive international scenario shows that CO 2 equivalent emissions for desalination in Dubai are 1.6 times larger than in California. The methods, decision support tool (WEST), and results of this study should persuade decision makers to make informed water policy choices by including energy consumption and material use effects in the decision-making process.

Comparing the Life Cycle Energy Consumption, Global Warming and Eutrophication Potentials of Several Water and Waste Service Options

“…LCA has been widely used to evaluate the system performances of water and wastewater technologies. For example, LCA studies have addressed specific aspects of conventional centralized drinking or wastewater systems, i.e., various options for drinking water supply systems [18][19][20][21], centralized and decentralized wastewater treatment [22][23][24], stormwater management strategies [25], or entire water and wastewater service systems [26]. Several recent review articles summarized the LCA developments in the water management area and emphasized the continuing research needs [24,26,27].…”

Evaluating the electricity intensity of evolving water supply mixes: the case of California’s water network

“…Finally, large-scale water-energy analyses are often limited by data availability [42,43]. Water utilities are hesitant to release detailed data on their systems, citing valid concerns about security and privacy.…”

Predicting the Specific Energy Consumption of Reverse Osmosis Desalination

“…Using our municipal-scale multiple linear regression model, we estimated SEC for the recently-opened Carlsbad Desalination Project in southern California to be SEC Carlsbad = 3.5 ± 0.23 kWh/m 3 , with the statistical uncertainty estimate successfully predicting the reported (likely conservative) SEC value of 3.6 kWh/m 3 [67]. Based on the model by Stokes and Horvath [68] of electricity and associated GHG emissions for water in southern California, replacing the current imported water supply in southern California with desalinated water from the Carlsbad facility would increase electricity consumption by a factor of 2.1. Consequently, a target reduction in municipal water use of over 53% is necessary to avoid increasing GHG emissions in response to substituting desalination for the baseline water supplies in southern California.…”