Emitting 1 kg of CO2 whilst using 0.2 kg of fuel. Where does that 0.8 kg come from?

Question

Hi There I didn’t pay much attention in sciences classes I am afraid.
But some one should be able to help me out.
I try to live as consciously as possible and deal with the environment and CO2 emissions. But one thing always stays with me: The volume of CO2.
People always talk about kg CO2 per… For example: diving 5 km in a average car would emit 1kg of CO2. I drive a Toyota Aygo, so a little less then average, but lets say could drive around 20km on 1 litre of fuel. That would mean I’ll use around 0,25 litre for 5 km.
Typical E10 fuel weighs around 0,85kg per litre. That should mean I used around 212 grams of fuel to produce 1kg of CO2. That math doesn’t count up for me… Where does the other 788 grams come from?

In: 8

Answer 1

Oxygen. Each molecule of CO2 has 1 atom of carbon (which will come from the CHCHCHCH hydrocarbon chains in your fuel), and 2 atoms of O2 coming from the air that your engine takes in during the combustion.