So the net fractional change in carbon dioxide for each breath is Similarly, the fractional amount of carbon dioxide exhaled, by mass is, assuming 5% by volume: It could just as easily be pound per pound. The number “.0006″ is really a fraction – which I am labeling in grams per gram. The molecular weight for moist air is about 28, which means that the air we inhale contains aboutģ.8 x 44 divided by 28 x 10000 = or 0.0006 grams carbon dioxide per gram of air But first we need to allow that “by volume” means (using carbon dioxide as an example)Ġ.038 carbon dioxide molecules per 100 air molecules, orģ.8 carbon dioxide molecules per 10000 air molecules.įrom above, we know that the molecular weight for carbon dioxide is about 44. To find out how much carbon dioxide is put into the atmosphere, we compare the amount of carbon dioxide (0.038% by volume) inhaled to the amount (4.6-5.9% by volume exhaled, Reference 3.), from the same web site. = 11.52 kilograms per day “processed” by breathing We now use this to estimate the kilograms of air processed each day, which isĠ.0005 kilograms per breath x 16 breaths per minute x 1440 minutes per day And, just for fun, I’ll use my respiration rate.Įach breath exchanges 500 cubic centimeters of air (Reference 2)Īssuming an air density of 1 kilogram per cubic meter, we can find out how many kilograms of air are exchanged for each breath:ĥ00 cm x cm x cm x 0.01 m/cm x 0.01 m/cm x 0.01 m/cmĠ.0005 cubic meters x 1 kilogram per cubic meter While I am writing this, my respiration rate is 16 breaths per minute, so this number seems reasonable. Again, some facts:Ī human adult breathes 15 times a minute, on average (Reference 1). Let’s try another way to estimate the amount of carbon dioxide our human releases. Based on carbon dioxide released through breathing (respiration) But our human would release carbon in other forms (feces, dried skin, shed hair, etc.) So there would be some solid waste as well as gas – but over long term, there would be some carbon dioxide released from that. We are assuming our human to be in steady state – so that net uptake by the body would be zero.
He/she would eat some fat as well, which has 9 kiloCalories per gram. There are a number of reasons this is probably an overestimate. So, let’s just call our estimate 700 grams of carbon dioxide a day, recognizing that the number is an approximate one. Assuming all this carbon is released as part of carbon dioxide, our human releases 733 grams of carbon dioxide (200 grams x 44/12). Sugar provides 4 kiloCalories of energy per gram, meaning that our human eats 500 grams of sugar each day. Molecular weight of carbon dioxide (2 x 16 + 12 = 44) All of the food eaten is in the form of sugars with carbon:hydrogen:oxygen ratios of 1:2:1.100% of this food is processed, with all the carbon returning to the atmosphere.The average human eats 2000 Calories (kiloCalories) of food a day.I start with some rather gross assumptions: And secondly, based on how much carbon dioxide is released with each breath. First, based on how many Calories a “typical” human consumes. The air is pumped in from the top of the tower into the laboratory building, when it is analyzed for the fraction of carbon dioxide and other trace gases.
It is located almost at the southern tip of Africa.įigure 1b Close-up of GAWS tower. 30-meter tall Global Atmosphere Watch Station (GAWS) tower from a distance.
I returned home, resolving to estimate how much carbon dioxide an average human gives off in a given day simply by breathing.įigure 1a. Standing for much of two days with groups of students at the base of the weather tower at the GAWS site at Cape Point, I found myself wondering how much we were contributing to the carbon dioxide in the atmosphere. The carbon dioxide record goes back to 1978, showing a rise comparable to that seen in the Northern Hemisphere. As part of their field activities, the students visited the Global Atmosphere Watch station (GAWS) at Cape Point, where carbon dioxide and several other trace gases are measured from the top of a 30-m tower. This blog was inspired by activities at the 2008 GLOBE Learning Expedition (GLE) in South Africa.
0 kommentar(er)
