Carbon dioxide or CO2 doesn’t get good press, everyone talks about limiting it, eliminating it or even capturing it… In a word, nobody wants it (except the trees)! But if the ton of CO2 is already a difficult concept to raise awareness, what about the tonne of carbon equivalent (or CO2e) which remains a downright abstract concept for most of us.
Every year, human activities emit more than 50 billion tons of greenhouse gases, which increases the greenhouse effect and increases climate change.
CO emissions2 are not linked only to industrial activities but also to our daily activities and therefore to our lifestyle. Each French person generates on average between 9 and 12 tonnes of CO₂ per year (according to sources).
What is the carbon equivalent (CO2e)?
We know that there are several greenhouse gases, starting with water vapour. the carbon dioxide (CO2) is the most common, but other gases, natural or artificial, have the same effect, with more or less marked actions.
Thus, 1 kg of methane, a gas resulting from organic fermentations, acts in the atmosphere as the equivalent of 25 kg of CO2, and 1 kg of nitrous oxide as 298 kg of CO2 !
All of the gases resulting from a manufacturing process are thus transformed and expressed in a single so-called equivalent unit. This quantitative measurement uses carbon dioxide as a reference. It is a “standard metre” to assess not the length but the greenhouse effect. It is expressed in carbon dioxide equivalent (equivalent carbon or equivalent CO2 or CO2e).
Can you see the difference better? CO2 is a gaseous compound and CO2she is a measurement of the greenhouse effect. This makes it possible to assess the carbon footprint of individuals and that of each daily activity.
CO2 comes from combustion because everything that burns contains carbon (except hydrogen): gasoline, coal, gas, wood, etc. In the flame, the carbon reacts with the oxygen in the air to produce energy (heat) and CO2.
An example to understand
The distinction between CO2 and co2It is easier to understand when we take a simple example.
The cow is a ruminant whose digestion process generates methane, the most abundant greenhouse gas after carbon dioxide. So the greenhouse gas emissions of the cow cannot be expressed in CO2 but must be in methane. She emits 70 kg per year.
To compare this value to the main greenhouse gas, carbon dioxide, we must transpose the value of 70 kg of methane into CO2.
Different greenhouse gases have different lifetimes in the atmosphere. A multiplier is therefore applied to methane emissions, which is the global warming potential (or PRG), generally expressed over a period of 100 years (PRG100).
| Gas | Lifetime (years) |
PRG20 20 years |
PRG100 100 years |
|---|---|---|---|
| Carbon dioxide (CO2) | >500 | 1 | 1 |
| Methane (CH4) | 12 | 72 | 25 |
| Nitrous oxide (N2O) | 114 | 289 | 298 |
As seen in this table, methane is 25 times more potent than CO2 : so we multiply the 70 kg of methane by 25 to obtain an equivalent in CO2 (CO2e), i.e. 1500 kg of CO2e.
Then, we can for example compare the 1500 kg of CO2and emissions emitted by the cow to a journey in a small gasoline-powered car that emits only CO2 (and no methane).
Thus, according to the manufacturer’s data, the Peugeot 208 emits an average of 104 g CO2 per km, i.e. 104 kg per 1000 km. The annual greenhouse gas emissions of a cow (1500 kg CO2e) are comparable to 14.423 km covered in a Peugeot 208. Surprising, isn’t it?
What is a ton of carbon equivalent (CO2e)?
If we insist that global warming does not exceed 2° Celsius, the average carbon footprint for an inhabitant of the planet should not not exceed more than 2.1 tonnes per year by 2050. There’s work to be done!
To get an idea of what a ton of CO₂ represents (i.e. half of our ideal quota), here are some correspondences that have the merit of enlightening us.
A ton of CO2 correspond to :
- 500 m³ of gas (the heating of a moderately insulated 50 m² apartment) or 380 liters of fuel oil
- 1 round trip Paris-New York by plane
- 6 round trips Paris/Marseille by plane for one person (according to the civil aviation calculator)
- 190 round trips Paris-Bordeaux by train
- 14,000 km with a Twingo in town
- 4300 kWh of electricity
- 1.8 tons of paper
- 4,700 kilos of potatoes
- 8,800 cups of coffee;
- 1,200 kilos of bread
- 250 kg of beef
The more a person consumes (food, heating, travel, travel, electronics, textiles, etc.), the more CO they emit2 and therefore of carbon equivalent.
