Oxygen consumption compared to carbon dioxide emissions.
We are all aware of our reliance on fossil fuels and their byproduct of greenhouse gases and poisons. But have you ever wondered about the oxygen needed to burn the fuel? As mankind burns more and more fuel, we are also burning more and more oxygen.
How much oxygen does a car burn?
The average U.S. citizen consumes more than 2 tons of oxygen per month. That is about 1.8 times more oxygen being consumed than carbon dioxide is being produced. ‡
Living a worse-case scenario
This graph assumes perfect conditions; however, the combustion engine is probably the most inefficient invention ever made. The explanation is fascinating:
In a perfect world the balanced equation for combustion looks like this:
2 C8H18 + 25 O2 => 18 H2O + 16 CO2 + Δ
Which means: Octane + Oxygen => Water + Carbon Dioxide + Energy
Or, 2 molecules of octane (pure gasoline) burned with 25 molecules of breathable oxygen (molecular oxygen) equals the byproducts of 18 molecules of water and 16 molecules of carbon dioxide.
Gas (C) + Oxygen (O2) = Carbon dioxide (CO2) or Carbon monoxide (CO).
In other words, we can see that a car burns much more oxygen than it produces carbon dioxide; meaning, we are depleting the oxygen from the atmosphere at a much greater rate than we are contributing global warming gases. Lifeforms can use the water and carbon dioxide to grow; however, the oxygen is locked away from a breathable form. The only feasible way to release the oxygen is through the complex and time-consuming process of photosynthesis; as you can see from the chart above it took the Earth about 2.5 billion years to fill the atmosphere with enough oxygen to sustain life.
But that is not the worst part of our story: much of the oxygen is bonded with pollutants, which permanently removes the oxygen from a form that plants or animals can recover. For example, most vehicles use fuel with a 87% octane rating. The other 13% are additives, such as: ethanol, heptane, lead and other impurities. This 13% bonds with the oxygen to create pollution like soot, carbon monoxide, sulfur and nitrogen dioxides (acid rain), and many more toxins and carcinogens. Additionally, the average vehicle emits about 3% unspent raw fuel in the exhaust, which also directly reacts with the oxygen to form pollution.
Adding insult to injury, the combustion engine only uses about 18%-20% of the energy to move forward. Most of the energy is lost to heat or the friction of breaking. Furthermore, most engines are worn out, and most drivers accelerate and decelerate at rates that burn extra fuel.
The bottom line: All these inefficiencies and byproducts have the detrimental side-effect of not only poisoning the Earth and her production of oxygen, but also eroding the ecosystem’s ability to repair itself. This unforeseen and unintended consequence forces humans to consume even more materials to fix the problems the pollution creates, which creates more pollution in the downward spiral of life.
* Measured by volume. If by measured by weight, a car burns about 4 times more oxygen than gasoline (octane); and, if measured by molecules a car uses 12.5 times more oxygen molecules than octane molecules.
** Sources: Science!
How much oxygen does a person breathe compared to a car?
As pictured above a car consumes as much oxygen in one hour as the average person breathes in 6.2 days.* This assumes that the car burns 2 gallons per hour with a perfectly efficient engine (above we saw combustion engines are far from perfect) averaging about 24.9 MPG. This is the new record-breaking national fuel economy, which is for a brand new car, with good fuel, traveling at average speeds without frequent stops. **We are also assuming the person has an active fitness level.
The oxygen in our atmosphere is being measurably and quickly reduced. Oxygen depletion, in our opinion, will soon be recognized as the greatest crisis humanity has ever faced. And it will probably happen in our lifetime. It is critical to start changing our habits and infrastructure while we still can. Because as we all know, we can’t simply stop driving our cars tomorrow. Which, by the way, is another great reason to ride a bike. Especially since one minute of driving your car consumes the equivalent oxygen that 5 people breathe in one day — that’s a lot of bicycling.
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Stay tuned for Scott’s upcoming book about oxygen depletion. Join our mailing list to get news. Update 2021: I’m still working on this. It’s been a tough project, but I plan to publish soon one way or another.