A few days ago, on a chilly Fall day, my grandson showed up to help me cut up some fallen tree branches as fuel for our fireplace. Afterward, we shared a cup of hot cocoa sitting in front of the fireplace, where as it happens we had an interesting conversation about what “carbon neutral” means.
The recently laid fire crackled and snapped as the orange and yellow flames licked up brightly over the oak logs, giving off a welcome heat. My grandson dragged his chair up closer to the fire and spread his palms out to intercept the radiant heat.
“Pop pop, what’s it mean: ‘carbon neutral’ ?”, he asked, adding, “My science teacher said that China has promised it will be carbon neutral by 2060?”
“Well that’s easy to explain sitting here in front of this fire”, I said. “Just look at this fire. The heat and light we feel and see in front of us is said to be “carbon neutral”. But if I go over to the wall there and turn the thermostat to high, the oil burner in the basement will go on and the heat produced that way is not carbon neutral. That fossil fuel source of heat pumps “new” carbon into the atmosphere. But the wood burning in the fireplace, over here, does not. The wood fire in the fireplace makes its heat from burning wood and is carbon neutral, but the oil burner heat is not.
“But why grandpa?”
“That tree branch we just just cut up out there, it is composed of cellulose and wood fibers. The tree’s green leaves produced all the parts of the tree from the water in the soil and the carbon dioxide in the atmosphere, using the sun’s energy. What do you call that process?
“Oh yeah! I know— that it’s ‘photosynthesis’”. My grandson happily and mechanically recited: “The leaves produce sugars from carbon dioxide and water, with chlorophyll in the presence of sun light” .
“Yes! And those sugars are combined to produce cellulose and other tissues that make up the tree that we are now burning in the fireplace.”
I turned to add new log to the fire, and asked, “So what’s happening in here? In the fire pit?”
“Ahh...... burning?”
“And “burning” is....?
“Is that oxidation?”
“Yes! Very good. Your teacher did well!”
I continued, “So you are saying that the wood is undergoing oxidation in the fireplace and in that process it gives off......just what? “
“ Oh yeah, I know,” he said, raising his hand as if eagerly answering a question in class. ”It’s oxidation. Oxidation is the combining of a fuel with oxygen to give off carbon dioxide and water’.”
“Good boy!!
“ So a carbon neutral process is one in which we only return the same carbon that was in the air, right back into the air. We add no new carbon to the air. In the fireplace the tree we are burning absorbed carbon from the air and when we burn it to get heat and light we are returning the same carbon right back into the air in the smoke ( which carries the CO2) that goes up the chimney.”
“ But grandpa, how is that different from the ‘not carbon neutral’ carbon dioxide that goes up in the air from the oil burner chimney?”
“OK, Look so when
we burn any fossil fuel, like coal, oil ( petroleum = petro =rock, oleum = oil, thus “rock oil”) even natural gas, we are taking carbon that was made by trees or other green plants millions of years ago and by ancient geological processes was buried underground for those eons. This carbon was separated from the atmosphere for millions of years until modern humans discovered these “dug up” (fossils) could burn very nicely. Since that time they continued digging this fossilized carbon up to provide useful heat and energy by burning it in the present- day atmosphere.”
Bringing it into the atmosphere and then burning it in the air produces “new” carbon dioxide. But this carbon is not really “new”. It had just been sequestered ( separated) from the modern atmosphere for millions of years and now as a result of human need for cheap energy it is being added to the existing burden of carbon that is presently in the air. “
“So grandpa what’s the big deal about carbon dioxide? Why is it called a “burden ”? Is it poisonous or something?”
No it is not “poisonous” but it does have a a special property. It is an excellent absorber of earth heat. Do you feel that heat coming off the fireplace? All bodies that are hot produce that kind of radiation. It is called Infra Red ( IR) radiation. The earth produces infra red radiation when the sun strikes its surfaces. Think of the heat coming off of a shopping center parking lot In mid summer. It is that heat that CO2 tends to absorb. Not the heat from the sun itself, but the radiant heat (IR ) produced when the sun heats a surface. It’s a simple equation— the more CO2 in the atmosphere—the more it absorbs earth heat. This heat is trapped in the lower levels of the atmosphere and acts like a heat blanket for the earth. The more carbon dioxide the hotter it get..
Since the 1850s when humans began using fossil fuels in greater and greater amounts the concentration of CO2 has been slowly and steadily rising ( today it is 0.04% or 400 parts per million or ppm) and clearly if there is more of a gas that causes the air to warm in the atmosphere, then we can expect the atmosphere to continue to warm up corresponding to the amount of “new” carbon we add to it.
In just petroleum alone ( not counting coal, and natural gas) the world consumes and burns about 100 million barrels of oil per day! That’s a lot of carbon going into the atmosphere.
So there. That is why nations and companies are now striving to become more “carbon neutral”. They do not want to be responsible for the bad effects of an overheated atmosphere.
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