A ‘carbon footprint’ as the name suggests, is essentially the evidence we leave behind us as we go about our daily lives. Unlike our footprints on a sandy beach however, which wash away at the next high tide, our carbon footprint remains a great deal longer.
It is a measure of the amount of ‘greenhouse gas’ released into the atmosphere as a result of our activities, whether directly or indirectly. A carbon footprint can be calculated per individual, household, community, organisation or even an entire nation.
The main greenhouse gases that contribute to our carbon footprint are:
Carbon Dioxide (CO2)
Nitrous Oxide (N2O)
Sulphur hexafluoride (SF6)
These gases are released into the upper atmosphere and sit like a blanket around the globe trapping heat – much like a traditional greenhouse at home where the heat enters through the glass and is then retained once inside. Unlike our greenhouse at home however, where the heat ebbs away at night, the greenhouse gases are accumulating at a rate which is faster than they can disperse so heat retention is increasing.
This accumulation of greenhouse gases is the cause of ‘global warming’ – which is the increase in average global temperatures over time.
This next section may take a couple of times to get your head around, but should be fairly self-explanatory.
In order to simplify the calculation of a carbon footprint each of the greenhouse gases is given a CO2 equivalent (CO2e) value and is normally quoted in metric ‘tonnes’. Because no two gases are the same each of the gases above are given a value, known as a ‘Global Warming Potential’ (GWP). The GWP essentially measures how damaging an individual gas is versus CO2 over a period of time. If we take Methane (CH4) as an example it has a GWP of roughly 30 meaning that 1 tonne of CH4 is 30 times as damaging as 1 tonne of CO2.
So if a company’s carbon footprint consists of 1 tonne of CH4 and 20 tonnes of CO2 their CO2e footprint would be:
(1t CH4 x 30 GWP) + 20t CO2 = 50 tonnes CO2e
I hope that makes sense!
Now finally, if you want to look at your individual carbon footprint there are a number of primary activities that affect it:
Personal transport (Car, Motorbike etc)
Public Transport (Bus, Train, Aeroplane etc)
Waste (do you recycle and does it all go to landfill?)
In all cases your footprint will depend on the volume and type of fuels you use. In the case of waste the more you recycle the less ends up in landfill – good for the re-use of raw materials and reduction of methane creation.
If you want to estimate your carbon footprint as an individual, business or otherwise there are many carbon footprint calculators on the internet that will help you do that. Some of these sites will also offer you the ability to cancel/reduce your carbon footprint by buying what are known as ‘carbon offsets‘. Many offset providers are highly ethical and re-invest your offset payments into beneficial projects such as renewables, reforestation and environmental projects in developing nations. Some are not so clear about this so feel free to ask them in detail before you part with your money. I will cover this area in future posts in much more detail.