Desalination is responsible for 200 million tons of CO2 emissions a year, significantly contributing to global warming.  Of course, global warming also contributes to drought highlighting the water-energy nexus.

Energy management is the most important aspect of reducing CO2 emissions associated with desalination.  Although Reverse Osmosis (RO) consumes 4 times less energy than thermal desalination processes, it still is responsible for about 2kg of CO2/M3, which is a lot.  The ability of desalination plants to reduce power consumption is limited by laws of physics.  As the number of desalination plants is expected to double by 2020, the desalination industry cannot add a new source of greenhouse gas emissions as countries mobilize to curb them.

With good energy management and coordination with the electric utility, a Reverse Osmosis desalination plant can have net negative impact on greenhouse gas emissions.  With well-designed desalination plants, the flexibility provided to the utility allows more variable renewable energy (VRE) sources like solar PV and wind energy than could otherwise be managed on the grid.

Since water can be easily stored (unlike electricity), flexible desalination is a form of energy storage.