Ball milling for gunpowder

I want a way to obtain gunpowder in peaceful mode. I want this because my aunt and I play in peaceful mode, as she's too scared of creepers. I'd like gunpowder so I can craft TNT for mining, which we're currently unable to get in Peaceful mode.

Bats produce guano in the same way that chickens lay eggs. A new redstone components, the rotator, rotates the block on top of it when powered. If guano, the sulfur block, charcoal, and copper nuggets are placed in a barrel, than each rotation would replace the ingredients except the copper nuggets with gunpowder.

Thank you.