Even if your cargo is "dirty" that doesn't necessarily mean you're okay with impurities (i.e. waste from whatever happened to be in the holds last). It's just d

Even if your cargo is "dirty" that doesn't necessarily mean you're okay with impurities (i.e. waste from whatever happened to be in the holds last). It's just dirty because it tends to leave more residue behind and that residue might be harder to clean off. Someone hauling coal or silver or something isn't going to be any happier having corn husks mixed in with their material than the recipient of a big load of corn would be to discover there's silver mixed in.