certain parts should not be eaten because they can be a choking hazard
if it is something that can be cut or reduced in size, then you can cut it and it to a meal
it may not sound very appetizing, but, certain parts could either be incorporated into a soup stock, or placed into a juicer and once it has been turned into a liquid you can use it as a garnish
if for whatever reason you cannot consume a portion of a vegetable, then you can either feed it to the local fauna in your neighborhood, or, you can use it to make compost