FYI: poopy diapers are not technically considered greywater and aren’t allowed per most greywater codes to be included in the laundry.

What I did when my son was in diapers was to scrap the poop off into our composting toilet, then put the poopy diaper into a bucket of water. We’d first wash the diaper in the bucket, then throw it into the laundry with the rest of the non-poopy diapers. The bucket of poopy wash water could be dumped into a flush-toilet, or put responsibly in an area of the landscape where people won’t access it and where the water will soak in (like a well mulched area behind some thorny roses). There could be situations where this suggestion wouldn’t be a safe practice, for example if there was a high ground water table and a drinking water well nearby, or if the site was very close to a stream/river/lake. In that case you’d want to dump the poopy water into a composter with enough sawdust to soak up the water.