How is the exhaled air composed?

Experiment: Carbon dioxide is produced during combustion processes and breathing

Table: Composition of dry inhaled and exhaled air (% by volume)
Inhaled airGasesExhaled air
1Noble gases1

Basis of calculation
We assume a boy aged 14-18 years with a basal metabolic rate of around 10,000 kJ / day. Body weight 65 kg. This is followed by a rough calculation exclusively for the basal metabolic rate without any particular physical exertion!

The following table shows the necessary food intake:

Food per day and kg body weightTotal amount at 65 kg (g)
1.2 g fat78
1.2 g protein78
6 g of carbohydrates390

We define average structures or the average oxidation state of carbon in food, from which a CO2-Molecule is formed:

  "Molar mass"
fat-CH2-14 g / mol
ProteinH-C-NH229 g / mol
carbohydrateH-C-OH30 g / mol

From this we calculate the "number of moles" of the average building blocks contained in daily food:

Fat building block78 g / 29 g / mol =5.6 moles
Protein building block78 g / 29 g / mol =2.7 mol
Carbohydrate building block390 g / 30 g / mol =13.0 moles

Each day it turns into CO2 educated:

(5.6 + 2.7 + 13) mol = 21.3 mol CO2.

Mass of CO formed2 = 21.3 mol x 44 g / mol = 937.2 g carbon dioxide.

A person alone breathes around 1 kg of CO per day with a basal metabolic rate2 out. At 25 C that is more than 500 liters of gas, i.e. half a cubic meter of pure CO2.

What is the annual amount of carbon dioxide exhaled by all 6 billion people?

1 kg CO2 · 6 · 109 People 365 days = 2.19 109 t CO2

People breathe around 2.19 gigatons of CO per year2 out.

This figure may seem huge, but compared to the sales figures for carbon dioxide on earth (170 gigatons) it is negligible. Incidentally, the technical anthropogenic emission is 7 gigatons. However, this apparently small deviation is sufficient, together with other greenhouse gases, to upset the equilibrium.

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