Climate change. It’s bad and it’s getting worse. The main cause is the burning of fossil fuels, which releases CO2 to the atmosphere. Carbon dioxide, as we all know very well by now, is a greenhouse gas, meaning it absorbs the Earth’s thermal radiation, preventing it from escaping into space.
A certain amount of this is good, without CO2 The Earth would be so cold that the oceans would freeze. But in pre-industrial times the concentration of CO2 in the atmosphere was approximately 280 parts per million (ppm). Now it’s 420 ppm, or 50 percent more. (You may be surprised to know that CO2 It’s still only 0.04 percent of the air we breathe, but that’s enough to ruin everything.)
What if we could remove carbon dioxide from the atmosphere? This is an idea that some startups are already experimenting with: it’s called direct air capture. The only problem is that removing the small fraction of C02 Air, which is made up of 99 percent nitrogen and oxygen, requires a lot of energy, and our hunger for energy is what got us into this mess in the first place.
How much energy would be needed? I’m glad you asked. We can estimate that using some fundamental ideas in thermodynamics.
Free gas expansion
Let’s start with a simple example. Let’s imagine that we have a box with a volume of 1 cubic meter and it has a divider that divides it into two equal halves. On one hand it contains nitrogen at atmospheric pressure and temperature, and on the other hand it is completely empty. Here is a diagram:
Calculation: Rhett Allain
We can model this gas as a bunch of little balls (nitrogen molecules) that bounce around. When a ball of nitrogen hits a wall of the container, it gives it a small push. All these pushes are what make the gas have pressure. In this case, it is a pressure of 1 atmosphere, or about 100,000 newtons per square meter. (A N/m2 also called pascal).