In an earth-like environment (above sea level), could an animal have an organ which could exert pressures equal to 5.5 bar 80 psi, enough to maintain liquid CO2? Taking in account that the temperature is max 0 Celsius. In addition, the organ would preferably have around 36 liters of liquid CO2. Any excess heat is dispersed throughout the body and evaporated if needed.

  • 9
    $\begingroup$ There's something of a disconnect between your title and your text. At earth-normal temperatures, the critical point of CO2 is 74 atm of pressure, so you're not going to get any liquid CO2 at 5.5. $\endgroup$
    – jdunlop
    May 23, 2021 at 20:19
  • $\begingroup$ @AlexP with machines that create more than 80 bars. $\endgroup$
    – Trish
    May 23, 2021 at 22:37
  • 1
    $\begingroup$ The edit doesn't correct the fundamental error in the question's assumptions, it remains unclear as a result because of the inherent contradictions. $\endgroup$ Jun 8, 2021 at 15:18
  • 1
    $\begingroup$ @Tortliena the organ produces that pressure, and the creature lives on land, if you look at some of the answers, they use the "aid" of underwater pressure to reach the specified 5.5 bar $\endgroup$
    – Dexyan
    Jun 8, 2021 at 18:41
  • 3
    $\begingroup$ @Dexyan your data is wrong. Just look into a phase diagram. 5.2 bar is for -56.6 °C! $\endgroup$
    – Trish
    Jun 9, 2021 at 13:37

3 Answers 3


You can easily get 5 atmospheres of pressure in an earthlike environment.



She is producing 5 atmospheres of pressure between her hands. And she is strong but not super strong. It is very earthlike there because she is off the coast of Indonesia.

Actually there are 5 atmospheres of pressure all around her because that is the pressure at 60 meters underwater. You can get even more pressure if you go deeper and there is a lot of deeper below 60 meters.

  • $\begingroup$ This does not answer the question. $\endgroup$
    – SRM
    May 23, 2021 at 22:10
  • 5
    $\begingroup$ @SRM: The question asks: "could an animal have an organ which could exert pressures equal to 5.5 earth atmospheres of pressure". The picture shows an animal whose lungs exert a pressure of 5.5 atmospheres. True, they are helped by the environment, but the question does not forbid it. $\endgroup$
    – AlexP
    May 23, 2021 at 22:27
  • 4
    $\begingroup$ Does it allow the creature to make liquid CO2, which is the question title? No. $\endgroup$
    – SRM
    May 24, 2021 at 3:32


Physics says: it's possible if you are a machine that can withstand extreme temperatures or pressures. Biology just says nope not within a window that can support any life.

How it came to that...

$$PV=nRT$$ That's the gas law. You want to get CO2 to go liquid. You assert that's at 5.5 atmospheres1. Or 557288 Pa. Let's assume that we want to compress 1 mol.

$$\frac {\text T}{\text V}=\frac{557288 \text { Pa}}{1 \text { mol}\times 8.31446261815324 \frac {\text{J}} {\text{K mol}}}\\=\frac{557288 \frac{\text{J}}{\text m^3}}{8.31446261815324 \frac {\text{J}} {\text{K}}}\\=67026.34019\frac{\text K}{\text m^3}$$

Now, under standard pressure and temperature ( $10^5\text{ Pa}, 273.15\ \text K)$, , 1 mol of gas takes 22.4 liters, or 0.0224 m³. We want to compress, as that's what OP said. So, we have an area of about 1 meter by 1 meter by 224 millimeters. It takes in one mol of air. Let's see what happens in case we pin the temperature to 273.15 K - an isothermic attempt.

$$\frac 1 {\text{V}}=\frac {67026.34019}{273.15}\frac{\text K}{\text {K m}^3} \\ V=\frac 1 {245.3829} \text m^3 = 0.004075\ \text m^3 $$ A muscle set that compresses our room from 22.4 mm to 4 mm height 2? No way, that can't work. We can't pin the temperature. Let's assume the best we can manage is halve the volume of the gland, that is technically 10 % more than typical muscles can manage, but halving is easier for math. Well, what happens to the temperature?

$$\frac {\text T_1}{\text V_1}=\frac {\text T_2}{\text V_2}\\{\text V_1}=2\times{\text V_2}\\\frac {\text T_1}{\text V_1}=\frac {\text T_2}{2\times \text V_1}\\2\times {\text T_1}= {\text T_2}\\T_2=546.3\text { K} $$ Eh... Nope! that's not an option, our creature just turned itself into well cooked, no, charred meat by trying to make CO2. In fact, it could set heavily processed leather on fire!


  1. CO2 only turns liquid at 74 bar at 31 °C. The cited number for CO2 comes from the triple point of 5.1 atm at -56.6 °C, which translates into 74 PSI at -70 °F. Nearly no bacteria can survive at that low temperature for extended periods - one of those rare few is Panagrolaimus davidi. The temperature is an essential information for the gas law.
  2. T/V is 8900154.27 K/m³ for the corrected pressure. Chucking in the temperature of 304.14 K gets us a required reduction of our initial 224 mm tall chamber to 0.034 mm or 34 µm. About half a human hair.


The gas law is like the moon, and the moon is a harsh mistress. Either you demand the clearly impossible from muscles, or you cook your creature alive. And there is no sweet spot available where the temperature increase for the required pressure and the available compression both are inside the range of supporting carbon-based life.

The closest equivalent organ that can create pressures by self-compression is the heart. It manages 120 mmHg - or 15998.7 Pa - or almost 1.6 bar. That's too low by a factor of 47 to make liquid CO2.


The gas law doesn't like your idea. You say 0 °C or 0 °F, and 5.5 bar, but you totally misunderstand the fundamentals of what Wikipedia tells you. That is not liquid CO2, as a simple gaze into a **phase diagram of CO2 will easily show. To have liquid CO2 at or above 255.37 K or 273.15 K demands pressures much higher. Note that the left bar is a logarithmic scale, not linear! In fact, the mere gaze into that diagram will tell you, that at 273.15 K, CO2 starts to go liquid at about 60-80 bar (math says: 72 bar) and stay so till above 5000 bar. For 255.37 K, we are at about 20-30 bar minimum. In fact, CO2 can't be liquid above the critical point of 31.1 °C - 304.25 K.

enter image description here

To have liquid CO2, you pick any temperature in Kelvin between the white triple point and black critical point, and then see where the line between blue and gray is there. That is your required pressure, which you can calculate with the gas law above. None of the solutions you will get is feasible for an organic being.

  • $\begingroup$ What about an animal with specific biological features to make itself more difficult to burn alive? $\endgroup$ May 23, 2021 at 22:21
  • 1
    $\begingroup$ @EkadhSingh we are talking about 273.15 °C or 523.67 °F. That is enough to set processed leather on fire $\endgroup$
    – Trish
    May 23, 2021 at 22:27
  • $\begingroup$ Ah well, it was worth a shot $\endgroup$ May 23, 2021 at 22:31
  • $\begingroup$ You should have just said nRT is constant, so PV is too, so to get 5.5x increase in pressure you need 5.5x decrease in volume. That would have let you realize that you made a significant mistake - it's not 224 to 4, it's 22.4 to 4. Also, you're assuming that it has to be done in a single chamber. Why wouldn't there be multiple chambers that incrementally increase the pressure? $\endgroup$
    – Rob Watts
    May 25, 2021 at 18:40
  • $\begingroup$ Transfer of the volume from chamber to chamber wouldn't work. But the missing decimal I must have read over. Doesn't help with the needed 74 bar @31°C though, where we really need to go to the horrible horrible half-hair thickness. $\endgroup$
    – Trish
    May 25, 2021 at 18:41

5.5 atmospheres is about 80 psi. The bite force of dogs can be measured in the 700 psi range, big cats in the 1000 psi range and bears in the 1200 psi range. It seems reasonable to me that an animal could evolve to produce this kind of pressure in other situations.

This is a list of top biters by body weight as a reference: https://en.wikipedia.org/wiki/Bite_force_quotient

  • $\begingroup$ that on a body that can change its shape and that is not fully internal. the only muscle that would be relevant is a heart. $\endgroup$
    – Trish
    May 23, 2021 at 20:56
  • $\begingroup$ "could an animal have an organ which could exert pressures equal to 5.5 earth atmospheres of pressure?" @Trish, the clear answer is yes despite your wish to complicate things with additional criteria. Note, the mouth IS an organ and thus many real animals, humans included are able to exert pressures in excess of 5.5 atmospheres. $\endgroup$
    – JonSG
    May 23, 2021 at 21:44
  • 1
    $\begingroup$ Bite forces are that high because they are measured on the needle sharp teeth which means a normal force divided by a tiny area gets a high pressure. $\endgroup$
    – Trish
    May 23, 2021 at 22:16
  • 1
    $\begingroup$ @Trish: So what? The question asks for 5.5 atm, it does not say anything about compression, volume or area. $\endgroup$
    – AlexP
    May 23, 2021 at 22:29
  • 1
    $\begingroup$ Title of question: organism which makes liquid CO2, is it possible? - basic knowledge of the gas law would tell you you need to compress gas from all sides - or rather withstand the equal pressure you exert onto the gas on all sides. Otherwise, you get a kettle explosion. $\endgroup$
    – Trish
    May 23, 2021 at 22:31

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .