It’s useless, it’s so much easier to flush the things.
Explanation: The joke plays on the double meaning of “log burner.” While most people would associate a log burner with a fireplace for burning wood, the punchline humorously shifts the meaning of “log” to bathroom slang (referring to human waste). The unexpected twist of flushing logs instead of burning them makes the joke funny by mixing two unrelated interpretations of the word “log.”