Most of us learned at some point in our lives that when we exhale, we are releasing carbon dioxide, or CO2, an invisible gas generated as waste through the millions of metabolic processes that maintain business-as-usual in our cells every day. But rarely do we pause to consider the significance of this unconsciously routine activity. In fact, few other activities allow us to participate so intimately in a global cycle that sustains all life on earth. If you’re the type of person who is inclined to be intrigued by the profundity of mundane truths, read on!
CO2 is fascinating in that it represents a beginning and an end in the most fundamental sense. As our cells’ mitochondria break down complex sugars to produce energy, CO2 is formed- a forgotten leftover once all the juicy electrons have been stripped away. But much as any gardener or urban composter knows, leftovers can sustain new life. Once expelled from its indifferent host, CO2 is free to reenter the atmosphere, where it resides for hours to decades, disappearing into a vast sea of nitrogen. Eventually, each molecule of CO2 respired will be absorbed by the biosphere again, sucked up through the tiny pores in a plant leaf or diffused across a bacterial cell membrane where it will be incorporated into sugar anew.
It is not just humans and animals that participate in the cycle of energy and breath. If you start looking for it, you’ll find evidence of electron-stripping, energy and CO2– releasing activities in nearly every corner of your life. Your houseplants respire CO2 as a byproduct of metabolizing the very same sugars they work to hard to photosynthesize. Soil, water, air and nearly every other non-sterile surface or media is filled with microorganisms that need sugars just like you and your plants, and likewise participate in the flow of energy. Even our machines strip electrons from once-living carbon-rich compounds, in a process not so different from what happens in your mitochondria (though cars and jet engines require much greater supplies of energy than humans or cats, thus we find ourselves extracting concentrated, fossilized plant remains from the bowels of the earth in order to keep them chugging).
Thus, as you zoom out a bit from your individual perspective, and it becomes remarkably easy to start aggregating breathers. Humans in a neighborhood. Cars on a highway. Blades of grass in a lawn. The soil beneath a cornfield. The amazing fact of the matter is, in fact, a very simple truth- we are all carbon-combusting machines, steadily chugging away at the biosphere’s second great energy source (sunlight is, quite arguably, the first). All of us except a fascinatingly weird little cult of microorganisms that I’ll have to touch on another time.
Okay, so maybe Morpheus cleared this all up a decade ago when describing the post-apocalyptic fields of human babies that serve as a primary energy source for our robot overlords. But our collective role in the global cycles of carbon and energy are important enough that I think it’s worth reiterating every once in a while.