Considering the hazardous effects of car and other vehicle exhaust when released into the atmosphere, I began wondering why we are not dominantly preventing the exhaust from entering into the atmosphere, for example by liquidizing it and storing it either in the driving vehicle or elsewhere?

My question is: why is it so difficult to liquidize the exhaust, in order to prevent it from entering the atmosphere? Or isn't it difficult at all perhaps?

Please note that it is not forbidden to theorize about adding any equipment and or chemical reactants to the vehicle.

P.S.: I would be equally interested in just storing the exhaust of a vehicle inside the vehicle by means of compression, rather than liquidization.

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    $\begingroup$ It would be an extraordinarily energy intensive process, more so than running the vehicle. Assuming you are trying to trap CO2, you would have to cool the hot exhaust to well below 100C, then store it for transport to recycle. Since burning a kg of gas produces 3 kg CO2, that means your storage tank is 3x the size of your gas tank. There are better ways to reduce emissions ;) $\endgroup$ – airhuff Mar 25 '17 at 16:16
  • $\begingroup$ @airhuff What about adding another gas/reactant to the CO2, so that, after the reaction, the gas could more easily be compressed or liquidized and stored? $\endgroup$ – Vincent Mia Edie Verheyen Mar 26 '17 at 0:35
  • $\begingroup$ If you could somehow bubble the exhaust through a strong base, that would absorb the CO2. The problems with that are that it's messy and dangerous to work with and you would need a lot of base. Although you could just say these are engineering problems that could be overcome...I don't want to discourage you from this line of thinking. One way to do this, rather than putting such a device in each vehicle, would be to centralize the collection of CO2 on a large scale at a power plant that makes electricity for everyone's electric cars. That has it's own advantages and disadvantages though. $\endgroup$ – airhuff Mar 26 '17 at 18:33
  • $\begingroup$ Here is something you might find interesting. This is an article about recovering the other major combustion product, water. It's a proposal for military vehicles in the desert to recover drinkable water from vehicle exhaust. Water would be much easier to collect than CO2 and this probably isn't relevant, but I thought you might find it interesting anyway. $\endgroup$ – airhuff Mar 28 '17 at 6:44