Green gas

The other night on call we were discussing the current issue of carbon emissions and global warming. My friend was conversing while drinking a diet coke. As he opened the can, out went a fiss of carbon dioxide. I though, well there goes some carbon into the atmosphere. Then I thought, how was that carbon dioxide put into the can? Well, energy was used to run the compressor to get the carbon dioxide from the air and then to put it back into the car. So, next I wondered just how much carbon dioxide in the atmosphere is from the carbonated beverages? About the time that I was doing this I burped, which had some more carbon as a by product of my own metabolism breaking sugars into CO2. It was about this time that the OR was ready and I had more important things on my mind.