In short, it means "whether the item must be thrown away or not". Usually there'll be a notice on the wrapper of the item you bought to indicate how it should be taken care of after unwrapped, to dispose or to recycle. The whole statement can usually be found inside the "necessity of disposal" notice block on the wrapper.

Some context would help. For me, ''the necessity of disposal'' = the need to make something go away. The phrase sounds a little bit awkward, and suited to business/official documents, or plans.