# How much yeast is necessary to produce the same amount of carbon dioxide that I exhale?

I think I might have bed bugs. I read that bed bugs are attracted to $\ce{CO2}$ and heat, I also know that yeast produces $\ce{CO2}$ as a waste product. Knowing that, I did some research and found this article on intructables.com which creates a "trap".

My gut instinct is that a 1/2 teaspoon of yeast will not produce anything close to the amount that a person exhales, but I don't know My question is, how much yeast would I need to create the same amount of $\ce{CO2}$ that I exhale on average in a day, per day?

What I know so far:

• We exhale $\pu{0.02 m^3/h}$ while resting or low activity (Oscar W. Richards and Florence W. Haynes, Plant Physiol. 1932, 7 (1), 139–144.)
• This graph (Figure 3 and 4 of above citation) shows the average $\ce{CO2}$ production per minute by yeast, but I don't know enough about chemistry to know what the units are or how to convert them to something useful (in my case, "useful" would be I need to buy x grams of yeast).

• The trap definitely works as I've caught 2 in 24 hours. However, catching them isn't my interest (I wouldn't be able to get rid of them all with a trap).

However, please don't be distracted by the bugs. The bugs themselves aren't the problem of this question; I'm trying to determine the quantities. I'm fairly naive when it comes to chemistry, but in my mind this shouldn't be a hard problem to solve. Unfortunately, I don't know how do the conversions or read the paper's to arrive at the answer but I'm still actively trying to figure this out.

• – Alchimista Nov 26 '17 at 10:10
• This was a pretty interesting post. But I still feel this should've been posted at the Biology.SE instead O:) – paracetamol Nov 27 '17 at 13:55
• Some pointers: (1) I haven't checked the links yet, but if you'd rather have the bugs heading for the "trap" you mention than your body, then you'll probably need to generate more $CO_2$ for your trap than the amount you exhale. (2) One way you can get rid of bedbugs is to spread copious amounts of dry ice over and under you bed (make sure you get the corners too), in your cupboards (bedbugs hide out in clothes too) and dump whatever dry ice you have left over into every nook and cranny you see... then spend a day camping outside before you head back in ;-) – paracetamol Nov 27 '17 at 14:02
• Thanks paracetamol. I think people are distracted by the bed bug thing however and I might edit that out. The obvious answers to that problem is to just call an exterminator. What I'm extremely curious about, to the point that I'm still actually teaching myself this stuff 3 days later, is to just know how much yeast is needed to create the same CO2 that I breath, bed bugs aside. – Oz Ramos Nov 28 '17 at 6:38
• Please don't use edit statements, this is what the edit history is supposed to be for. Make your case for a person that reads it for the first time, include everything relevant into the question body. – Martin - マーチン Nov 28 '17 at 8:02

First, I would question whether the amount of $$\ce{CO2}$$ is relevant or the concentration (or if more convenient, partial pressure). There is no way for the bed bugs to integrate over the entire trap vs. the bed. If you have a concentration gradient from bed to trap, it should work.
Second, yeast is a catalyst. The amount of $$\ce{CO2}$$ made depends on the amount of available food (the yeast will multiply to keep up). In the simplest terms, if you want the yeast to produce as much $$\ce{CO2}$$ as you do, you have to feed it the same amount of food that turns into $$\ce{CO2}$$.
Because yeast and humans have a slightly different diet, you have to interpret "same amount of food" a bit. In human metabolism, all carbon from foods with calories (i.e. not fiber) is used in biosynthesis or ends up as exhaled $$\ce{CO2}$$. In an adult who doesn't gain or lose a lot of weight, you can estimate the amount of $$\ce{CO2}$$ produced from the amount of food taken in. In yeast metabolism, depending on the conditions, either most carbon turns into $$\ce{CO2}$$ (when there is plenty of oxygen) or into ethanol (when there is a lack of oxygen). For bed bug traps or baking, you want the former, while for brewing, you would want the latter.
For practical purposes, though, I think the total amount of $$\ce{CO2}$$ is moot (see my first point). As long as you have a source of $$\ce{CO2}$$ in the trap and remove the source of $$\ce{CO2}$$ in the bed (i.e. sleep elsewhere) and keep the room warm, there should be a nice $$\ce{CO2}$$ concentration gradient for the bugs to follow.