Saturday, December 23, 2006

Calculate your Carbon-Footprint.

Ever wanted a ready-reckoner as to your carbon footprint? If so, Donnachadh McCarthy (who's family are originally from Cork, I would think, as it is my Grandmother's maiden name) has written an article in The Independent in which are some handy conversion factors. The carbon footprint is oddly named, since it refers to the "weight" of CO2 impressed on the sky, in tonnes of carbon dioxide NOT carbon. To convert this to an equivalent of carbon, multiply each tonne of CO2 by (12/44) or about a quarter. First of all, electricity. To convert this into an emission of CO2, first work out how many kilowatt hours of electricity has been used by your household during the past 12 months. For our own household, it is 3,062 kwh (according to the electricity bills), and so multiply this by 0.43:

Hence: 3,062 x 0.43 = 1,316.7 kg = 1.3 tonnes of CO2.

Next, gas/oil. Again, from the bills you can work out how many kwh of gas you have used, and in our case that is 18,237 kwh, which is to be multiplied by 0.19, giving:

3,465 kg = 3.5 tonnes of CO2.

[For completeness, If you have oil-fired heating and used 2000 litres of oil, the conversion would be 2,000 x 2.68 = 5,360 kg = 5.4 tonnes of CO2.
If it is coal-fired, and 2.5 tonnes of coal were used, then that equates to 2.5 x 2.42 = 6,000 kg = 6 tonnes of CO2].

Car use: this is worked out on the mileage, and so for an annual 8,700 miles, multiply by 0.36 = 3,132 kg = 3.1 tonnes of CO2. Now, we do not own a car, and instead walk or use public transport for longer distances. Hence although on this basis, our CO2 contribution is zero, there is some output.

Flights. The recommendation is to take the number of short-haul flights (e.g. London-Paris; London-Edinburgh) and multiply by 0.2 tonnes of CO2. For medium-haul flights (e.g. Edinburgh-Ankara; Cardiff-Cairo), multiply by 0.8 tonnes, and long-haul (e.g. London-Sydney) multiply by 2 tonnes.

For the electricity and gas/oil, add the two together and divide by the number of adults in the household. So, for us that is: 1.3 + 3.5 = 4.8/2 = 2.4 tonnes of CO2 each. Add zero for car use, and 2 medium haul flights each (London-Prague) = 2 x 0.2 = 0.4. Hence we have a carbon footprint of 2.8 tonnes of CO2 each. I am relieved that our combined "household emissions" of 5.6 tonnes is less than the 6.2 average according to DEFRA, and a good deal less than the 66 tonnes estimated for one well-off Hertfordshire family! The entire family of Friends of the earth press officer Neil Verlander apparently produces a mere breeze of 1.7 tonnes of CO2!

Energy Balance wishes you all a Merry Christmas and a less energy intensive 2007!

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