Monday, December 11, 2006

Your Carbon Footprint Counted.

A new report by the Carbon Trust, funded by the U.K. government, has concluded that each of us "emits" almost 11 tonnes (10.92 tonnes) of CO2 per year. This does not refer, of course, to our bodily emissions, but that produced from all the activites surrounding an average life in the U.K. It is worth mentioning that the report refers to "The cost in carbon (per person, per year)" when it is really carbon dioxide that is being counted. As an effective mass, this equals: (12/44) x 10.92 = 2.98, or nearly 3 tonnes of carbon.
For comparison, the average American causes 19 tonnes of CO2, which is roughly in the ratio of the statistic that if all the world lived a European lifestyle, it would take three planet Earths to support it, but five planets to live as the US do, in terms of the energy resources consumed. I noted previously that we have just passed the point of "going into the red" in terms of resources used, and have exceeded what can be provided in a sustainable way - put more choicely, "we have begun to eat the planet!"

As a matter of interest, lets see how much CO2 each "body" does emit. Let's assume an average food intake of 2,000 "calories" per day, and that it is all burnt up in the form of glucose. The heat of combustion of one mole (180 grams) of glucose (C6H12O6) is 2830 kilojoules. This is equal to:
2830/(4.18 x 180) = 3.76 kilocalories per gram. Now, one "calorie" as referred to in food is actually one kilocalorie, hence that 2000 calories is really 2000 kilocalories. Hence 2000 kcal/3.76 kcal/g = 531.9 g of glucose.
"Burning" 531.9 g of C6H12O6, according to: C6H12O6 + 6O2 --> 6CO2 + 6H2O, produces:
(6 x 44/180) x 531.9 = 780.12 grams of CO2/day. Which per year is 780.12 x 365 = 284,743.8 grams = 285 kg = 0.285 tonnes CO2. While this is quite a bit less than the 11 tonnes that are our responsibility in total, it is not included in the figure for "food", and hence I revise the annual figure upward from 10.92 tonnes to 11.2 tonnes!

The figures break down as follows. Almost a fifth (1.95 tonnes) of that 12.2 tonnes arises from recreational activities - everything from car trips, to visiting gyms and leisure centres with a heated pool, watching the good old "goggle box" or floodlit evening football matches. Home heating accounts for 1.49 tonnes of CO2, so any form of energy efficiency such as double-glazing, loft insulation, and keeping internal doors shut all helps to reduce this. It is reckoned that 1.39 tonnes iof CO2 are generated by catering and food generally (cooking and refigeration, plus indirect emisions from food production including drink products and services etc.). Within this heading is included growing crops, producing packaging, manufacturing, distribution and recycling. Add to this the 0.285 tonnes emitted bodily from digestion and we have 2.235 tonnes from "food" altogether!
The Carbon Trust message is not suggesting that we curtail these activities, but just think more about what we are using, and how we might use less. For example, 2 kg of CO2 can be saved for each journey under three miles when we walk rather than use the car (I don't have car!), and 30 kg by swiching off the power in your house at night. A massive 2,300 kg (2.3 tonnes) of CO2 could be saved by using recycled paper in the office (trouble is that often this doesn't work very well in printers). An additional 1.37 tonnes are apparently generated by "household activities", and this includes lighting, running appliances such as vacuum cleaners, and also the electricity used to produce household furnishings and even the building itself, from making bricks to delivering the furniture etc. to put in it. Clothing and footwear amount to one tonne of CO2, commuting is reckoned at an average of 0.85 tonnes (I am self-employed and work from home most of the time, making my contribution close to 0.00 tonnes per day or per year), "Hygeine", for example taking a bath instead of a shower adds an extra 50 kg of CO2 to the personal burden, and so on runs-up 1.34 tonnes of the tarrif. Aviation (a subject I have mentioned many times since it consumes over one fifth of the entire national transport fuel budget of 57 million tonnes), by each of us results in the emission of 0.68 tonnes of CO2.
Reckoning aviation fuel in terms of n-octane (C8H18), and that it burns according to:
C8H18 + 12.5O2 --> 8CO2 + 9H2O, than means one mole, 114 grams, of fuel produces 352 grams of CO2. Hence the annually consumed 12 million tonnes of fuel is expected to produce (352/114) x 12 million = 37 million tonnes of CO2, which implies 37 million/0.68 = 54.4 million person-flights. If that were all used in one return flight (as most people will want to return home again), then we have somewhere over one million individual flights flown per year. I don't know what the figure is recorded by the airline companies? It's a lot, anyway, and a population of 60 million each contributing 0.68 tonnes of CO2, implies 40 million tonnes of CO2 annually just from plane flights.
Education ("information" really) accounts for almost half a tonne (0.49 tonnes) of CO2, including travel, books and newspapers, so 172 kg (0.172 tonnes) are for school buildings, 13.6 kg for books and the "school-run" in a dreaded 4 x 4 ("Hummer" or "Chelsea Tractor" as we know them affectionately over here), rated at 1.2 miles, five times per week during term time, was 200 kg (0.2 tonnes). Communications emissions, including from computing, amount to 0.1 tonnes (100 kg), and for example mobile phone chargers accounted for up to 70 kg of CO2 per year. It is to be noted that sending letters represented only 0.01 kg!

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