The problem with the CO2-based SMOC is that it tends to cool the contents. Heating the whole mug not only takes too much energy but results in a cup that's too hot to be optimal. Nevertheless at least a little heating is always helpful.

This mug of coffee contains, in its base, a small amount of water which is heated separately from the coffee, just enough to continually emit steam. The water vapor is piped up through one way valves near the top. Thus the heat loss from the larger part of the mug is avoided and the cup can steam for half an hour while the coffee is actually heated a bit.
-- Voice, Jul 04 2021

OVR (Only Vaguely Related) Self_20heating_20sake_20cup
[normzone, Jul 05 2021]

//The problem with the CO2-based SMOC is that it tends to cool the contents.//

and it will dissolve in the coffee to some small extent, changing the taste. A bit like flat seltzer water.

//water which is heated separately from the coffee, just enough to continually emit steam.//

You haven't mentioned any kind of motivation behind this idea, I can think of one I like: this coffee mug obfuscates the time the coffee was made, I like it. It could be added to a strategy of nipping out of work early for the underemployed - back when I had an easy job I could complete by lunchtime, I employed a strategy involving a spare jacket, keys, no screensaver and a fresh coffee just before leaving. This idea enhances the effect of the latter. [+]
-- bs0u0155, Jul 06 2021



random, halfbakery