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

Published: May 1, 2013
Authors: Heather Cooley, Matthew Heberger 
Pages: 37 

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.

In California, and in other regions dependent on hydropower, electricity prices tend to rise during droughts, when runoff, and thus power production, is constrained and electricity demands are high. Additionally, electricity prices in California are projected to rise by nearly 27% between 2008 and 2020 (in inflation-adjusted dollars) to maintain and replace aging transmission and distribution infrastructure, install advanced metering infrastructure, comply with once-through cooling regulations, meet new demand growth , and increase renewable energy production. While rising electricity prices will affect the price of all water sources, they will have a greater impact on those that are the most energy intensive, like desalination.

The high energy requirements of seawater desalination also raise concerns about greenhouse gas emissions. In 2006, California lawmakers passed the Global Warming Solutions Act, or Assembly Bill 32, which requires the state to reduce greenhouse gas emissions to 1990 levels by 2020. Thus, the state has committed itself to a program of steadily reducing its greenhouse gas emissions in both the short- and long-term, which includes cutting current emissions and preventing future emissions associated with growth.  Desalination ­­– through increased energy use – can cause an increase in greenhouse gas emissions, further contributing to the root cause of climate change and running counter to the state’s greenhouse gas reduction goals.

There are several ways to reduce the greenhouse gas emissions associated with desalination plants, including (1) reducing the total energy requirements of the plant; (2) powering the desalination plant with renewable energy; and (3) purchasing carbon offsets.

“Even renewables have a social, economic, and environmental cost, albeit much less than conventional fossil fuels. Furthermore, these renewables could be used to reduce existing emissions, rather than offset new emissions and maintain current greenhouse gas levels. Offsets also raise concerns; caution is required when purchasing offsets, particularly on the voluntary market, to ensure that they are effective, meaningful, and do no harm,” said Cooley. “Energy use is not the only factor that should be used to guide decision making. However, given the increased understanding of the risks of climate change for our water resources, the importance of evaluating and mitigating energy use and greenhouse gas emissions are likely to grow.”

The Key Issues for Seawater Desalination series is an update to the 2006 Pacific Institute report Desalination with a Grain of Salt, which has proven to be an important tool used by policy makers, regulatory agencies, local communities, and environmental groups to raise and address problems with specific proposals, downloaded nearly 700,000 times. Researchers conducted some 25 one-on-one interviews with industry experts, environmental and community groups, and staff of water agencies and regulatory agencies to identify some of the key outstanding issues for seawater desalination projects in California. The resulting reports address proposed desalination plants in Californiacosts and financing, and energy and greenhouse gas emissions, with a forthcoming report on marine life and coastal ecosystem impacts.

Download the full report.

Go to the press release.

Download the Series:
Key Issues in Seawater Desalination in California:

dotProposed Facilities (2012) dotCost and Financing (2012) dotMarine Impacts (2013)
dotDesalination, With a Grain of Salt (Full report, 2006)  dotEnergy and Greenhouse Gas Emissions (2013)