Huh, that’s what I was thinking. He went with a guy who did the ‘honey dipping’ one time, cleaning out septics from schools and restaurants. Looked exactly like this stuff, gray cement-y stuff they had to shovel and brush off the walls of the tank. He said the grease debris smelled worse than anything else they had cleaned out.
I worked in an office behind a Denny’s just after college. The days they had the grease truck come we could barely stay at our desks for hours after.