Plants are made of air

May 21, 2015 by Joshua
in Nature

I used to think plants used energy from the sun to pull material out of the ground and that they were made of that material, meaning they were ultimately made of earth. Seems plausible, but wrong.


They use energy from the sun to pull carbon from carbon dioxide and make themselves out of that. In other words, they’re made of air. They get some material from the ground, but not much. How much? When you burn a log, most of the plant goes back into the air and the ash that remains is mostly what it took from the ground. I think they get water from the ground too, but that water probably got there from rain, which is kind of like air too.

I find it amazing. Giant redwoods that tower hundreds of feet and are big enough to drive a car through are mostly made of air.

You can also learn about the environment and the greenhouse from this observation.

That’s why plants help with the greenhouse effect. They take the greenhouse gas carbon dioxide from the atmosphere. What do they do with it? They make themselves out of it. So when the plant dies, if it decomposes its carbon goes back into the atmosphere. Cutting down forests puts the carbon dioxide that was in their trees and plants back into the atmosphere.

Oil, coal, and other fossil fuels burn the remnants of plants that took carbon dioxide from the atmosphere a long time ago. Even if we restored all the forests we’ve cut down, we still couldn’t remove all the extra carbon dioxide we put in the environment from the plants we burned that had been underground as untapped fossil fuels.

If the carbon dioxide in the atmosphere is warming our planet enough to flood cities, disrupt our food supply, make many species extinct, defrost regions storing carbon that will release yet more of it and augment the effect, and so on, and we want to prevent the loss of life and culture it might bring, we’d probably want to get the carbon dioxide that we put into the atmosphere back into the ground.

I haven’t looked up the science, but I’d guess we’d have to get something like the volume of all the oil and coal we brought to the surface back into the ground. Since we probably got as much energy as we can out of the fossil fuels we used, we’d have to get another energy source to get the carbon back out of the air and into a solid or liquid. Trees do it without any effort from us, but once we regrow forests, I don’t know how we can keep making more trees. We could use solar and wind energy, but we plan to use that energy to drive society.

Anyway, my point wasn’t to get into the greenhouse effect, just to point out something about nature I find fascinating and beautiful and to explore some results of the effect.

Before closing, I searched the web on this and found the master speaking on it. Now I remember seeing it before, but, for the record, I knew some of it before seeing Richard Feynman speaking on it.

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