The Pacific Institute has published the next instalment of its series on Key Issues For Seawater Desalination in California, this time looking at energy requirements and associated greenhouse gas emissions for desalinated water.
As the institute’s Heather Cooley explained in D&WR (February/March 2013), its objective is to identify some of the key outstanding issues for seawater desalination in California. The first report, in July 2012, updated the status of the many desalination proposals and projects in the state, while the second in December 2012 looked at costs and financing of projects.
The Pacific Institute says that its analysis shows energy requirements for seawater desalination average about 15,000 kWh per million gal of water produced (3.96 kWh/m³).
By comparison, the least energy-intensive options of local sources of groundwater and surface water require 0-3,400 kWh per million gal (0‑0.90 kWh/m³); wastewater reuse, depending on treatment levels, may require 1,000‑8,300 kWh per million gal (0.26-2.19 kWh/m³); and energy requirements for importing water through the State Water Project to Southern California range through 7,900‑14,000 kWh per million gal (2.09‑3.70 kWh/m³).
The report also says that desalination by increasing energy use can cause an increase in greenhouse gas emissions, further contributing to the root cause of climate change and running counter to California’s greenhouse gas reduction goals. It lists several ways to reduce the emissions associated with desalination plants, including
1. Reducing the total energy requirements of the plant
2. Powering the desalination plant with renewable energy
3. Purchasing carbon offsets.
However Cooley says, “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.”
The latest report can be downloaded from the Pacific Institute’s website