Probably 15-20m3 a year I would guess. Moving back to the farm from central-heated later this year so time will tell. We have recently had a good thinning in the wood though so there's a pile to get through and I'd like to do it quickly and efficiently. Electricity won't be an option in terms of working in the wood / yard unfortunately.
Our kitchen wood-burner takes 11" lengths max and an open fire can take twice that, so I've been mixing between 11" logs and splitting into IBCs and 44" billets and stacking in the wood for cross cutting later. All splitting by hand so far. Not sure which is more efficient but the billets seem more satisfying! I'm quite tempted to go for a 1m length spitter for billets.
Surely with a 22" log you can load it one side of the wedge, split and then load a new one, or one of the halves, for the return journey? I don't see why 11" would be the limit. Or do you mean loading two 11" lengths to split in one pass?
Going back to power source, I think petrol seems the way to go but am seeing both PTO and tractor hydraulic options as alternatives. I don't fancy revving the tractor to get the PTO RPMs up which I assume I'd have to.
Many thanks to everyone offering their experience. It's much appreciated. Especially as you can see I'm pretty confused about what's going to be the best option.