I’m just mentioning it because I think that toilet paper as a single use item billions of people use at least daily is a much bigger issue of wasting trees than books - which last for decades and are very useful
There are modern toilets with integrated automated bidets and dryers. But they are unfortunately a bit expensive.
It’s spelled flak, not flack. It’s a German abbreviation from Flugabwehrkanone, which means aerial defense cannon.