Climate change. It’s bad and getting worse. The main cause is the burning of fossil fuels, which emit CO2 to the atmosphere. Carbon dioxide, as we all know by now, is a greenhouse gas, which means it absorbs the Earth’s thermal radiation, preventing it from escaping into space.
Some amount of this is good – no CO2 The earth would be so chilly that the oceans would freeze. However, in pre-industrial times, the concentration of CO2 in the atmosphere was about 280 parts per million. It is now 420 ppm, 50 percent higher. (You may be surprised to learn that WHAT2 It’s only 0.04 percent of the air we breathe, but it’s enough to ruin everything.)
What if we could remove carbon dioxide from the atmosphere? This is an idea that some startups are experimenting with – it’s called direct air capture. The only problem is removing a tiny part of the C02 the air, which is 99% nitrogen and oxygen, takes a lot of energy, and our hunger for energy is what got us into this mess.
How much energy would it take? I’m glad you asked. We can estimate this using some basic thermodynamics concepts.
Free expansion of gas
Let’s start with a plain example. Imagine we have a box with a volume of 1 cubic meter that has a partition dividing it into two equal halves. On one side it contains nitrogen at atmospheric pressure and temperature, and the other side is completely empty. Here is the diagram:
Calculations: Rhett Allain
We can model this gas as a bunch of diminutive balls (nitrogen molecules) bouncing around. When the nitrogen ball collides with the wall of the container, it pushes it slightly. All these pressures cause the gas to have pressure. In this case, it is a pressure of 1 atmosphere, or about 100,000 newtons per square meter. (One N/m2 also called Pascal).