Converting methanol into methane
Methanation is a process whereby synthesis gas is converted to methane.  

$\ce{CO + 3H2 -&gt; CH4 + H2O}$

Methanol, like nearly all organic molecules, can be gasified to form synthesis gas at elevated temperatures.  

$$\ce{CH3OH -&gt; CO + 2 H2}$$

(Note: the gasification reaction is actually a complex balance of many types of reactions.  Often times mixtures of $\ce{CO}$, $\ce{H2}$, $\ce{H2O}$, and $\ce{CO2}$ are obtained.  The reaction above is the ideal case where complete conversion is achieved.)

Thus a process for converting methanol to methane could proceed via gasification followed by methanation. 

However, since methanol is made commercially from methane by essentially the reverse process, this route is unlikely to be economically viable!