Key Issues in Seawater Desalination in California: Energy and Greenhouse Gas Emissions

Interest in seawater desalination in California is high, with 17 plants proposed along the California coast and two in Mexico. But removing the salt from seawater is an energy-intensive process that consumes more energy per gallon than most other water supply and treatment options. A new report from the Pacific Institute series Key Issues for Seawater Desalination in California describes the energy requirements and associated greenhouse gas emissions for desalinated water and evaluates the impact of short- and long-term energy price variability on the cost of desalinated water.

Energy requirements are key factors that will impact the extent and success of desalination in California. Key Issues for Seawater Desalination in California: Energy and Greenhouse Gas Emissions shows energy requirements for seawater desalination average about 15,000 kWh per million gallons of water produced. By comparison, the least energy-intensive options of local sources of groundwater and surface water require 0 – 3,400 kWh per million gallons; wastewater reuse, depending on treatment levels, may require from 1,000 – 8,300 kWh per million gallons; and energy requirements for importing water through the State Water Project to Southern California range from 7,900 – 14,000 kWh per million gallons.

“Beyond the electricity required for the desalination facility itself, producing any new source of water, including through desalination, increases the amount of energy required to deliver and use the water produced as well as collect, treat, and dispose of the wastewater generated,” said Heather Cooley, co-director of the Pacific Institute Water Program and report author. Conservation and efficiency, by contrast, can help meet the anticipated needs associated with growth while maintaining or even reducing total energy use and greenhouse gas emissions.”

Desalination is a reliable source of water, which can be especially valuable during a drought. However, building a desalination plant may reduce a water utility’s exposure to water reliability risks at the added expense of an increase in exposure to energy price risk. Energy is the largest single variable cost for a desalination plant, varying from one-third to more than one-half the cost of produced water. Because of its high energy use, desalination creates or increases the water supplier’s exposure to energy price variability.