# CO 2 emissions **URL:** \ **Category:** Factual Questions\ **Created:** [September 8, 2008, 6:34pm UTC](https://boards.straightdope.com/t/co-2-emissions/462652 "2008-09-08T18:34:41Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![vison](https://avatars.discourse-cdn.com/v4/letter/v/e47774/32.png) [@vison](https://boards.straightdope.com/u/vison)\ **Post date:** [September 8, 2008, 6:34pm UTC](https://boards.straightdope.com/t/co-2-emissions/462652/1 "2008-09-08T18:34:41Z")
How can using 1 litre of gasoline emit 2.4 Kg. of CO2? This is what my AirCare result sheet tells me - AirCare being the mandatory emissions test that all passenger cars have to go through before insuring in BC. ---
**Author:** ![Rysto](https://avatars.discourse-cdn.com/v4/letter/r/ecccb3/32.png) [@Rysto](https://boards.straightdope.com/u/Rysto)\ **Post date:** [September 8, 2008, 6:42pm UTC](https://boards.straightdope.com/t/co-2-emissions/462652/2 "2008-09-08T18:42:16Z")
Over 2/3rds of the mass comes from the oxygen, which comes from the air. ---
**Author:** ![Interconnected\_Series\_of\_Tubes](https://avatars.discourse-cdn.com/v4/letter/i/13edae/32.png) [@Interconnected\_Series\_of\_Tubes](https://boards.straightdope.com/u/Interconnected_Series_of_Tubes)\ **Post date:** [September 8, 2008, 6:42pm UTC](https://boards.straightdope.com/t/co-2-emissions/462652/3 "2008-09-08T18:42:18Z")
Some quick googling yields about 0.75g/ml as gasoline’s density, or about 750 grams for a liter. However, remember that burning gasoline is a **combustion** process; chemically, burning is an oxidation reaction. This turns gasoline (a mixture of carbon and hydrogen with a few trace contaminants and additives) into combustion byproducts, generally CO, CO2, and H2O. All those extra oxygens come from the atmosphere and contribute to the mass of the emissions. As oxygen is slightly heavier than carbon (with atomic masses 16 and 12, respectively,) your statistic doesn’t seem unreasonable. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [September 8, 2008, 6:45pm UTC](https://boards.straightdope.com/t/co-2-emissions/462652/4 "2008-09-08T18:45:31Z")
Ballparkin it: About 80% of the mass of gasoline is in the form of carbon. 1 liter masses about 750 grams, so that’s about 600 grams of carbon. It’ll take about 1600 grams of oxygen to convert that to carbon dioxide. 1600 + 600 = 2.2 kg. So that 2.4 kg number is about right. ---
**Author:** ![vison](https://avatars.discourse-cdn.com/v4/letter/v/e47774/32.png) [@vison](https://boards.straightdope.com/u/vison)\ **Post date:** [September 8, 2008, 6:48pm UTC](https://boards.straightdope.com/t/co-2-emissions/462652/5 "2008-09-08T18:48:48Z")
Thanks. I just didn’t think that combustion would add so much mass/weight. Makes sense now.