Water Week

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Desal emissions; 0.08kg to 5.2kg of CO2/m3: low, if the process was 100 percent driven by waste heat; if NSW coal, then 5.2kg of CO2 per m3

Posted by waterweek on 25 September 2007

The analysis of emissions’ intensity of various desalination technologies showed that MSF distillation emissions could be as low as 1.98kg of CO2/m3 if the process was 100 percent driven by waste heat, according to the WWF’s Phil Dickie.

Emissions vary depending on fuel mix: According to Dickie most MSF facilities were coupled with power generation plants. Likewise Reverse Osmosis (RO) emissions varied considerably with the fuel mix used for power generating, from 0.08kg of CO2/m3 in Norway to 3.08kg of CO2/m3 in Portugal. The emissions intensity of California power was lower than the US average, reflecting more use of natural gas and less of coal.

US, Australian figures: The Pacific Institute estimated an average seawater desalination energy demand of 3.4kWh per m3, which would translate to carbon emissions of 0.94kg per m3, according to Dickie. “Performing a similar exercise for the other US high growth low water states however produces much higher emissions of 2.2kg of CO2 per m3 (Texas) and 2kg of CO2 per m3 (Florida). An Australia Institute analysis of the greenhouse impact of Sydney’s ultimately proposed 500,000 m3/day RO plant held that the energy demands would be 4.93kWh per m3 and emissions would equate to 5.2kg of CO2 equivalent per m3 from the State’s mainly coal fired power stations. Annual greenhouse emissions would be 945,000 tonnes of CO2 equivalent – in more colourful terms the institute noted “The emissions are the equivalent of putting another 220,000 cars on the road, or burning 2 litres of petrol for every 1,000 litres of water.”

Kwinana a good model: “Across Australia, the Western Australia Water Corporation’s newly operational Kwinana desalination plant is setting new records as the largest so far constructed in the southern hemisphere and the largest anywhere to be powered by renewable energy. The 130,000 m3/day plant uses the same power as 30,000 homes and increased the corporation’s energy use by 50 per cent, but purchases the equivalent of all its power requirements from a newly constructed windfarm. Clearly, the Western Australian precedent is to be preferred if desalination is not going to become a key contributor to the climate change problems.”

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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