EcoWorldly

Ten credible on line calculators gave Carbon Footprints that ranged from 27 000 to 76 000 pounds of carbon emitted a year for the same input data. An understanding of the greenhouse gas (GHG) emissions associated with what we do and consume will give us a better chance of reducing our emissions than using such inaccurate calculators. 

What’s the problem?

J. Paul Padgett and collegues at Vanderbilt University and the University of Washington analysed the results obtained using 10 carbon footprint calculators from credible organisations including; American Forests, Bonneville Environmental Foundation (BEF), CarbonCounter,The Conservation Fund and the Environmental Impact Agency (EPA). Their results are published in the Environmental Impact Assessment Review 28 (2008). They identified the massive range refered to above, that ammounts to a difference of  180% between the lowest and highest figures and concluded that “Given their prevalence and potential influence, CO2 calculators can provide even greater public benefit by providing greater consistency and clarity.

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My feeling is that this is a very mild conclusion in keeping with an academic Journal. In reality, the calculators are almost useless because if this is any kind of a sample the result is only accurate to something like ±100%. Maybe even more worrying is the lack of transparency regarding the calculation methods used. It means the person using the calculator can not understand the issues and implications of what they are doing to any depth.

What are the difficulties?

The difficulty in using the available carbon emissions information is a result of the following:

Limited Good Data

A recent study of literature in the UK failed to find a single example of a complete life cycle analysis having been done on any fruit or vegetable. So even if you are considering a very specific issue the data you can find is likely to be incomplete and to contain poorly explained assumptions and extrapolations.

There Is No “Average” Person

Most calculators give the option to use your own or average data for the calculation. Its always tempting to use the average if you don’t have you own data readily available. However, unless you look at your consumption you can’t know if you are average.

Different Conversion Factors

Conversion factors are used to convert the consumption data (eg miles travelled, electricity used and waste generated) into the associated GHG emission. There are real differences that effect these factors, such as the fuel used to generate your electricity and drive your car, which are not well taken up in many calculators. More worrying is the different figures used for seemingly well defined things such as the conversion factor for petrol.

Incorrect Assumptions

One calculator stated their calculation reduced the footprint by 50% if the user bought “local food” This is a major error as it has been shown that local food can have a larger footprint than transported produce if for example it is grown in a greenhouse. Others actually have arithmetic errors in their calculator’s interface.

What Should You Do?

The easier a calculator is to use the more assumptions are being made and the less likely it is to accurately measure your situation. So you first of all need to realise that to get a good understanding of your carbon footprint and how you can change it will take a real effort.

You need to spend time looking at more detailed information than you get in a calculator and have to be able to understand the issues rather than relying on a standardised calculation.

A few examples which show the kind of understanding you need to develop are discussed and will be the subject of future more detailed posts. 

Motorcar Travel

One of the major portions of your GHG emissions comes from burning fuel in your cars. As the emissions are directly proportional to fuel consumption, a first reaction might be to sell your gas guzzler and buy a compact car. But the new car also has GHG emissions associated with its manufacture and your gas guzzler will use less petrol if you travel slower, share lifts, drive more carefully and maintain it well - all of which have no carbon footprint of their own!

Of the total emissions of a car over its life, approximately a third result from manufacture and two thirds from the fuel used. So investing in hardware to reduce fuel consumption is at least worth considering. However, the capital spent on a car could possibly have more impact on reducing emissions by iinvesting it elsewhere.

GHG Emissions Of Some Foods

Many calculators take no account of individual consumption patterns while a few give different GHG emissions for basic differences like veganism. The figures below show some of the differences between different foods.

data from New York Times and DEFRA

This confirms what we are told continually - that meat has a very large carbon foot print. But what is not so well known is that cheese also has a high GHG emission and that chicken is comparatively low. You need to know whether our organic or free range chickens have higher emissions than the battery chicken with its 6 week industrialised life.

Air Travel

Your air travel on your holiday has a big impact on your carbon footprint but so does snow skiing in Dubai as will the planned air conditioned beach. Minimize the energy intensiveness of your activity while on holiday can balance the GHG emissions of your trip. Of course a boat trip or staying closer to home could also help.

Business air travel can also contributes strongly but can be reduced by replacing travel with other means of communication such as video conferencing and online meetings. A previous post looked at the carbon footprint of conferences in some detail,

Managing Waste & Recycling

Composting organic waste will reduce methane emissions that would occur in landfill fermentations. This could be significant because methane has a 20 times more severe effect of the greenhouse effect than Carbon Dioxide. However, eliminating unnecessary waste by careful food planning and control could be more beneficial.

Recycling is another means of reducing GHG emissions by supporting the packaging material manufacturers to avoid the higher energy inputs for virgin materials. 

What’s Next?

I expect to be writing in more depth on aspects of the carbon footprint in future posts and would like to hear your feeling and suggestions.  

 

photo credit: by digivu at Flickr under a Creative Commons license.  

figure: by author

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