Water Week

EWN Publishing

Power hungry seawater desalination adds to CO2 emissions: Reverse Osmosis at 1.78kg of CO2/m3 clear winner over thermal distillation

Posted by waterweek on 25 September 2007

Regarding the contribution of emissions to climate change, seawater desalination – in most cases the most energy intensive of potential water sources – would add in a significant way to an existing process, said the WWF’s Phil Dickie. A comparison of the emissions intensity of various desalination technologies – using an average European fuel mix for power generation – showed the great advantage of;


•  Reverse Osmosis (RO) (1.78kg CO2 per m3 of produced water); over

•  thermal distillation technologies of multistage flash (MSF) (23.41 kg CO2/m3); or

•  multiple effect distillation (MED) (18.05 kg CO2/m3).”

Huge water-processing demand-load: “Precise figures depend on the location,” wrote Dickie, “but to take one example, the Pacific Institute estimated that the water sector was responsible for 19 percent of electricity use and 32 percent of natural gas use in California in 2001. The Institute calculated that the then current proposals to provide six percent of the State’s water through seawater desalination would have increased water-related energy use by five percent over 2001 levels. Spain’s Carboneras desalination plant uses one third of the electricity supplied to Almeria province. In a general sense, the increased demand for energy for desalination implies a commensurate increase in the carbon emissions linked to climate change.”

Clear advantage of Reverse Osmosis process: “Worldwide, the electrical power generating sector is the world’s most significant single generator of carbon emissions, responsible for 37 percent of global emissions, Dickie wrote. “Always operating large scale desalination plants are also generally unsuited for variable power sources and tend to add to the base load power requirements most likely to be generated by burning fossil fuels.
Reference: Phil Dickie, WWF for a living planet, ‘Making Water – Desalination option or distraction for a thirsty world?’, June 2007.

Erisk Net, 23/9/2007

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