If anyone can find a reference on the amount of CO2 produced during bread making it would be easy enough to calculate. I haven't been able to find any relevant sources except this old one [1] which mentions that the alcohol content in bread can be as high as 1.9 percent (which sounds quite high to me, but it's hard to critique when they don't explain their methodology).
How do you distinguish between evaporated water and respirated CO2?
As an aside: My understanding was that most breads don't vent all that much CO2. Bread doughs are not risen in processes that leave the opportunity for rapid bubble formation and dissolution; If they did, baking after that first rise would give you a layer of thick dense bread, and another layer of fluffy bubble-bread on top.
Water 611 g, eyeballed 600 ml in old glass measuring cup
After kneading 1408 g
After first rising 1416 g
After "punch down" and second rising 1406 g
Formed into loaves, waiting to rise before putting in oven
Edit: After baking, 1271 g
I'm using a creaky old Ohaus dual pan balance, surplus from an industrial lab. The process is not entirely "quantitative" in chemistry terms because there are some minor gains and losses. I have to flour the kneading cloth to prevent sticking, some dough may get lost on my bowl, and so forth.
[1] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1709087/?page=1