It does collect random mob drops but that's easy enough to fix. The main reason for the cleaner was that for some reason my carts were leaving saplings and apples on the ground, presumably because they don't always shave the whole tree. So I made 6 new carts, removed the fertilizers, added the cleaners, and everything has gone fine, there are no entities on the ground now so lag is minimal. Quick note... don't forget to set your compact solar engine to 1 higher than your coal engine on the little priority settings. That way the solar runs when the cart isn't under leaves and when it is under leaves the coal engine starts.