Carbon footprint methods, assumptions and tools

[part of a series of posts on my carbon footprint:]

Firstly, however you do these sorts of measurements, it is a good thing to do as it facilitates action. It helps set targets, create a sense of achievement, and helps you prioritise the potential actions you might take. And, not doing it is no excuse for inaction – changing light bulbs, buying local, organic vegetables, and and turning off all your appliances, don’t affect your lifestyle or challenge your values at all, and will no doubt save you money.

Doing the work I do, and liking to be rigorous about things, I have looked into the tools and assumptions. Rather than come at them from my professional sustainability background, I have come at it as a semi-normal citizen in the hope I can make recommendations that others can come up with. So, if you are reading this and want to debate the paradigm and highest level assumptions from a strategic sustainability perspective please do…but just appreciate what perspective I am coming from ; )


Basically, I would recommend you use your government’s recommended site (e.g. UK government’s site), to get a feel for where you are relative to the population. These sites are usually easy, look nice, and easily comparable. This one is also good: Zerofootprint It’s quite comprehensive and has instant graphics for comparison with other cities and countries. And, I would also highly recommend doing NEFs Happy Planet Index calculation, which looks at your happiness as well as the negative ecological impact you are having. COIN also did a survey of all the online calculators in Spring 2007, so you can choose one yourself:

You can review my calculations and assumptions in this spreadsheet.

What I did initially

For me, I initially used the Resurgence calculator. After a quick survey of all the alternatives, it seemed to be the most rigorous. It is very detailed, and uses the conversion factors that punish you the most for flying etc. Then, through trying to be consistent with fellow CRAGers I used the downloadable form and conversion factors from the CRAG site.

So, those calculations formed the basis of my footprint calculation for last year. This would probably take the average person an hour or so to do, depending on how many individual trips you have to find details for, and whether you have your energy bills to hand. And, because the CRAG form doesn’t do food, I used a separate calculator for food which takes about 15 minutes.


And, so I could see how it compares and whether to recommend it to others, I tried the UK government’s site. This asks slightly different questions to the previous calculations but only takes about 15 minutes. For the same reason (cross-comparison), I looked at for some of my flight calculations.

And, I was recommended a calculator from a Green Accountancy firm that compared the conversion factors for all the other calculators in one place, and chose what they thought were best (I have used some of their recommendations in my 08-9 calculations, even though their tool is really targeted at small-medium businesses, not individuals).

To give you and idea of what the differences between all these tools mean, here are the different results I got with the same information:

Comparing a 2500km trip London to Istanbul

Resurgence for a flight= 1350kg

DEFRA (UK government) for a flight = 275kg

COINet for the train= 275kg

DEFRA for the train = 100kg

You can see from this there is quite a variation in the results! Note that I chose these numbers to deliberately illustrateĀ  the significance. So, if you read the above figures, and hear a part of yourself saying something like “well, look at that, there is so much uncertainty…I should just fly” I would suggest you have a good hard think about whether that is the best part of yourself, or some part that is selfish, greedy, and looking for a reason not to do anything ; ) I would invite you NOT to use the uncertaninty in the detail to dismiss the overwhelming evidence that your behaviour and your decision-making are contributing to a problem that your children’s grand-children will still be dealing with. Just don’t….and if you want to discuss this, call me ; )

Other tools

Although English and German railway booking systems will estimate carbon for you, I did not use their systems: For the UK For Europe:

This online tool to calculate distance is very good, and I used it to calculate the distance from Calcutta to Kunming You can actually calculate emissions on this site too, using the DEFRA recommended conversion factors. This one is also useful

And I did experiment with an online tool for tracking key information. This is REALLY good if you are perhaps a home-owner and want to ‘see’ on a graph when your power consumption has really increased. Although it is a good start, it isn’t comprehensive or flexible enough for my liking:

And, if you want to look at the detail of the factors some of these calculators use, and how they come up with the numbers, check our the DEFRA and CarbonTrust sites for their accepted standards.

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