Rubbish trucks

There's a huge waste tip north of Perugia and lately huge trucks with matching huge trailers have been literally pouring in from several different directions (to lessen the obvious profusion of them I suspect)  They probably come up the E45 to Umbertide and Perugia before splitting off to sneak up local roads.. The question is what do they carry (sweetly smelly and always the same) and where are they coming from? Naples maybe?  I ask this in case any of you have noted a daily procession of smelly trucks passing your way.