I mean I have a vague concept of how Trees convert sunlight to energy through photosynthesis using CO2+Sunlight releasing O2. As well as consuming water and nutrients. But my understanding is that the majority of the water is lost to evaporation and as little as 5% is utilized by the tree. Consequently it is hard to fathom where all the mass for a giant sequoia comes from. Are they Breatherians or something?
Carbon from the air.
Pretty much. Plants get most of their mass from the air. Photosynthesis splits carbon dioxide and fixes carbon into more complex organic compounds.
Yup: trees intake CO2 and exhale O2. The ‘C’ has to end up somewhere.
Trees are basically cellulose and lignin. Cellulose is (C6H10O5)n and lignin is an almighty mess but still composed of only carbon, oxygen and hydrogen. Add to that a tiny bit of phosphorus, manganese and the like to make the cellular chemistry work, and you can build a tree from nothing more than trace elements from the soil, carbon, hydrogen, oxygen - or water, carbon-dioxide and sunlight.
Depending on the species a live tree can have as much as 50% of its weight in water. Kiln dried wood typically has only 6%-8% moisture content, but naturally dried wood products may retain as much as 20% moisture content.
All those carbs in a tree have a lot of hydrogen atoms in them. They don’t contribute much to the mass of the tree, but still, there are lots of them. They have to come from somewhere. That’s what happens to a lot of the water that plants suck up – the H2O gets split up so the H’s can go into hydrocarbons and carbohydrates, along with all the C’s (which contribute most of the mass) from the CO2 sucked out of the air.
Some of the O gets into those complex molecules too, but there’s a net excess of O left over, which wafts out into the air. And then we get stuck breathing that.
Additional note of interest: By radio-tagging the atoms in the incoming H2O and CO2, it’s possible to trace exactly which O’s from which source end up where in the result, and which O’s get released as left-over O2. It’s not at all random. It’s very precisely predictable which atoms end up where.
Right. All of the atmospheric oxygen produced actually comes from water.
In glucose, the main basic product of photosynthesis, the carbon and the oxygen come from CO2, and the H from water. But because carbon and oxygen are much heavier than hydrogen about 94% of the weight of glucose comes from the CO2.
I remember reading a book in which they described a lab experiment, where the testers very carefully weighed the soil around a tree before planting , and at a later point. The amount of mineral loss due to root uptake was incredibly minuscule.
Yep. That experiment was done centuries ago - let me google PHSchool.com Retirement–Prentice Hall–Savvas Learning Company
Van Helmont's experiments on plant growth - National 4 Biology - BBC Bitesize
Misconceptions about Helmont's Willow Experiment.
At the time, the experimenter concluded that the plant was almost entirely made of water - because it took up almost no soil - but now we know that the atmosphere is the major source of the matter of the plant
Might be worth noting that when you burn wood you effectively reverse the process of the tree’s growth, producing energy, CO2 and some water. The ash that’s left behind is mostly the fraction of the wood that didn’t come from the air. Googling suggests this varies with the species and is typically around 1 to 2 percent.
Not just by burning wood. Anytime you exhale, you’re losing mass by adding a C to each O2.
Obligatory xkcd link
Plants also require several macronutrients for growth, plus another 10 or so minerals, which they get from the soil. However, these are needed in much smaller quantities. The major nutrients are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. Of these, most nitrogen ultimately comes from the air, although it first has to be “fixed” and changed from N2 to a form that plants can use by atmospheric, chemical, or biological processes.
I would’ve thought more than 50%. When I was building my house, fresh cut logs felt like they weighed 1/2 a ton. When completely dry, I could pick up one end with one hand.
I sense a new diet craze! We’ll call it Heavy Breathing.
No. Better make that “Light Breathing.”
Not much. An adult human at rest uses about 100 watts of power.
Carbon’s higher heating value is 32.8 million joules per kilogram.
So you burn about 3 micrograms of carbon per second.
About fifteen breaths per minute, so one every four seconds, so each exhaled breath contains about 12 micrograms of carbon.
Math might be a bit different since we’re actually metabolizing sugar/fat/protein instead of burning graphite, but it’s probably in the same order of magnitude.
That doesn’t seem right.
Let me try some simple math. Astronauts use about 0.84 kg of O2 per day. That’s about (0.84 kg) * (1000 g/kg) / (2 * 16 g/mol) * (12 g/mol) = 315 g of C per day. Or about 14 mg of C per breath, which is about four orders of magnitude larger than your estimate.
I think the difference between burning atomic C and metabolizing organic carbon is large.
This article How Fat Is Lost from the Body | Live Science claims
The researchers showed that during weight loss, 84 percent of the fat that is lost turns into carbon dioxide and leaves the body through the lungs, whereas the remaining 16 percent becomes water, according to the study published today (Dec. 16) in a special Christmas issue of the medical journal BMJ.
“These results show that the lungs are the primary excretory organ for weight loss. The water formed may be excreted in the urine, feces, sweat, breath, tears or other bodily fluids, and is readily replenished,” the researchers said.
I have to admit, my estimate seemed suspiciously small, and your approach (starting with how much O2 a body uses per day) seems sound. And of course your result is reasonable: 315 grams of carbon equates to 787 grams of glucose, which by itself will get you through a day… But I’m at a loss for how understand why my approach was so far off. The heat of combustion for carbon, glucose, and fat are all in the same order of magnitude; if you oxidize X grams of fuel, you get Y joules of heat. If a resting adult makes 2.4 kilowatt-hours of heat in a day, that would seem to set an upper bound on how much fuel is being oxidized in that period. 