Pip description says it drops 75% of the eaten mass as dirt. It eats 0.3kg per cycle apparently, which as observed seems to be 7% of the growing branch. The branch itself says it weighs 8kg so 7% of that would be 560g. Wild Pip eats the same amount just every 4 cycles. So a wild arbor tree after recent changes can support 4 domestic Pips or 16 wild ones.
Issue is that i cannot see them ever drop any dirt. Even after running 100 cycles. Neither wild nor domestic.
With debug, put a pip in a room with an arbor tree. Leave it 100 cycles, see that there is no dirt.