My wife came across the Jean Pain compost water heater recently, and I've been really intrigued by the idea. I haven't found a great compact design though, and most of the information I see online treats it more like a fun project than something that could be iterated on and refined. Would love to find somewhere to trade ideas on this and potentially replace some or all of gas water heater.

Here's a decent post about the idea: https://waldenlabs.com/compost-water-heaters-from-jean-pain/