Leachate tank explosion - GIF

[NortonDommi]

What is leachate and why does it explode?

Leachate in this instance is the liquid from anaerobically decomposed, some of the nastiest, stinking , vomit inducing black goop you will ever encounter. Usually associated with Methane gas. If you ever smell this stuff burn you will wish you hadn't.
In landfills there should be vent tubes deep down right to the base that bleed off the Methane gas as it develops. Usually flared off but some landfills use the gas to burn for heat, supplement incineration and/or power gensets for electricity.