[Born to Conserve]

Calcium carbide is created by heating minerals with calcium and carbon. When combined with water, acetylene is produced. Under pressure, and in time, acetylene combines with itself to produce many complex organic molecules. This is obvious. Aluminum carbide, produced similarly, releases methane in contact with water. Other metal carbides produce methane and acetylene. Before life evolved, the environment was deeply gunked with hydrocarbons.

[Reily]

There are interstellar hydrocarbons

http://astrobiology.com/2022/02/interstellar-hydrocarbons-degradation-chemistry-in-diffuse-clouds.html

So very plausible!