Farting and “black goo” at 20 days?

NSFW because it’s a bit gross.

Any more experienced fasters have input?

Day 21 has dawned and my guts are rumbling, farts and tarry black goo are erupting. Last time I did 15 days and 15 days interrupted by a singular Mexican meal (nachos supreme with pulled chicken) and this phenomenon had already ended at day 10 not to return.

I’m assuming this is the bacteria dying off inside my digestive tract and cascading down.

Any expectations of when this should end? I really don’t want this to happen at work where I’m unable to take a quick shower since this substance appears to be immune to toilet paper.

Also any tips on remedying Keto rash would be helpful as the internet is scant on the topic.