Proper disposal of used PiezoFlush?

After doing three INIT FILLs with PF in my 7900 to prepare it for Piezography Pro, I have accumulated a fair amount of spent PF. It’s nice to be able to reset the chip on the Maintenance Tank to save on trashing all the plastic, but this also means you end up with lots of ink and PF which will need to be properly disposed of, even if you put in heavy wads of paper towels to soak up some of it.

Does PF (and for that matter the Piezography inks as well) need to be handled as “hazardous household waste”?’’ How do you handle disposal of the liquids in your Maintenance Tanks at InkjetMall and Cone Editions?