Carbon Dioxide – The Dance of Life

Aug 16, 2018 | Global Food and You |

The Dirt:

Are you alive? Then you can thank carbon and carbon dioxide! Both are critical components of our atmosphere and all life on Earth. Without them, we would have unpleasantly cold temperatures, no plants to eat, and no trees to keep the earth in balance. In fact, we would not have life on Earth as we know it.

Not to get too groovy, but carbon originally rode the waves of stardust traveling through space after the Big Bang to eventually make its way to Earth. Carbon takes all forms and can be as soft as the graphite lead in a pencil and as hard as a diamond.
Carbon is also part of carbon dioxide (CO2), a chemical compound made of one carbon and two oxygen atoms. This compound, along with other gases, such as water vapor, methane, nitrous oxide and ozone, are greenhouse gases. They absorb the sun’s heat and either radiate it to space, back to Earth, or to another greenhouse gas molecule. This can actually be a good thing if we want to continue to enjoy grilling outside in July, as the Earth’s average temperature would be about -0.4°F without the greenhouse effect, compared to today at roughly 57.2°F.
CO2  is .04% of the Earth’s atmosphere.
C02 is 3.62% of greenhouse gasses.  Out of the 3.62 %, 3.4% is a result of human activity.

Where does Carbon and Carbon Dioxide come from?

We can live our lives and enjoy our favorite activities thanks to carbon, which is 18% of a human’s body mass. Carbon is a building block of muscles, carbohydrates, and fats. And we also eat carbon in the form of glucose (carbon, hydrogen, and oxygen atoms). When the human body ‘burns’ glucose for energy, it produces carbon dioxide as a byproduct, which is eliminated through your breath. This process is called cellular respiration. Every day you breathe out about 2 pounds of CO2 into the atmosphere.

CO2 also comes from the carbon in the Earth. Oceans, decomposing plant material, and rock layers within the Earth’s surface all have carbon as their building blocks. As plants, animals, and reptiles die and decay, they become buried under layers and layers of mud, rock, sand and even ancient seas. The biggest carbon dioxide sources are deep-sea vents and volcanoes. Forest and grass fires are also natural CO2 emitters. As we mentioned, humans, along with all mammals, are CO2 providers.

Anthropogenic (man-made) CO2 comes from the burning of the Earth’s carbon. All that vegetation and those dead animals and reptiles, hundreds of feet below the surface for millions of years, are now oil, gas, and coal. Burned as fossil fuels, the carbon goes back into the air. It may not seem obvious, but every time you start your car, heat your home, or turn on your lights you connect with old dinosaur bones or vegetation buried from millions of years ago.

The Carbon Cycle – the Breath of Life

Plants emit the oxygen that all mammals breathe, and in turn, mammals exhale COfor the plants. Of course, plants don’t only provide us with oxygen— they also give us the nutritious food we eat!

This brings us to The Carbon Cycle. The Earth’s atmosphere consists of one big inhale and exhale of CO2.  Picture the Earth as one gargantuan convective movement of air and water. Vegetation, landmasses, and oceans inhale CO2. Mammals, oceans, and volcanoes exhale CO2.  This process creates a balance of carbon in the atmosphere.

Global carbon cycle. Numbers represent flux of carbon dioxide in gigatons (Source: Figure 7.3, IPCC AR4).

But the Earth is not always balanced— through the Carbon Cycle there is leftover carbon dioxide that is not inhaled by the Earth. Today, the atmosphere has 409 parts per million (ppm) of CO2. Over the past 400,000 years, it has fluctuated between 200 to 300 ppm. It was only recently (within the past 115 years) that it began to rise to today’s level. It is because of this increase that many scientists associate CO2 with the Earth’s changing climate.

The Bottom Line: 

Carbon is critical for life on Earth. We need it for the air we breathe, for the plants we eat, and for our bodies to stay healthy. Next time you eat a kale salad or start your car, you can thank the stuff of stars.