When we say "mud" some of us think of the boot-sinking, foot-grabbing clay dirt mixed with
water that forms in places where water stagnates, and it's really unpleasant to walk through. Mud is also something beautiful: when we mix clay with water and throw in some straw and even
cow manure, mix it and make mass with it, it can be used for many things, including to store heat.
Here is an example of using mass made out of cob to store heat overnight in a very small cabin.