Carbon/Energy Savings from reduced use of mains water

[Mark Siddall]

I was at a seminar the other day and the chap presenting remarked that energy/carbon savings can be made by reducing mains water consumption. On the face of it, its nothing to surprising really.

This said does anyone have any ideas where I can find more information on the potential energy savings from reducing water consumption? I have had a scout around various sites but haven’t come across what I’m after.
(I am looking for info along the lines of kWh saved per litre and kg CO2 saved per litre. Savings per cubic meter may be a suitable alternative unit.)

Mark

[Nick Grant]

Mark

I've seen some silly figures quoted. One was along the lines that UK water treatment uses as much energy as if every home had a tumble dryer running all day – this is very wrong!

Figures I'm currently using from water UK are 0.586 kWh/m3 to treat and pump mains drinking water and another 0.63 to treat the resultant sewage. Assume all electric to calculate CO2. Typical UK 2.4 person household is using around 150 l/person (smaller households use more per person).

With efficiency measures and a little care – like not leaving taps running or washing half loads in a machine – its quite reasonable to get down to 80-100 l/person.

So lets say 2.4 person home (I know..) saving 50 l/p = 0.12kWh/d saving, there are better reasons to save water.

However to heat water from 10C to 42 C needs 37kWh/m3 before allowing for efficiencies and losses which could double it. Most domestic water is heated to some degree.

Surprisingly rain and greywater systems typically use significantly more energy than mains although they normally only do WC flushing.

So prioritise measures that save hot water and go for efficiency rather than recycling.

I'd be very interested if anyone would like to argue otherwise.

Nick

Water UK report link for pdf download:

http://www.water.org.uk/home/policy/reports/sustainability/indicators-2005-06/towards-sustainability-2005-2006.pdf

[Mark Siddall]

Thanks Nick. Some good pointers there.

Mark

[Anonymous]

This is what a contact in the water industry says:

Energy is our largest cost for pumping and treating water and sewage. So we have a fiancial incentive to be as efficient as possible. I think we use something like 5% of the electricity in Yorkshire and nationally the industry uses something like 2%.

“If people use less water obviously we pump and treat less, less power is used so water efficiency can reduce our carbon footprint.

However, as we're required to do more and more in terms of treatment, particularly sewage treatment these operations are becoming more energy intensive so our carbon footprint may increase a bit like everyone upgrading to PS3s.

As energy is now expensive and we are lovely people we are looking at ways of reducing our bills/carbon footprint by generating our own, so in the future, being water efficient will have minimal effect if it all works.”

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