some things to think about
I researched the composting toilet a few years back.
The electrical consumption on the model I looked at was pretty minimal - just
a circulating fan,
But what stopped me is that these things need an "exposure" on more or less a daily basis, in order to keep the enzyme farm from dying out. As pretty much a weekend sailor, that killed it for me. But for liveaboard use they look
to be a good fit.