Keep herb stems for stock, infusions, or sauces
Use celery leaves in stock or salads.
Save vegetable ends in a bowl in the fridge to simmer at the end of the week for a vegetable stock. Strain and freeze or use.
When using a jar of sauce, after emptying the jar, add a couple of tablespoons of water to the jar, put the lid in, and give it a shake. Pour that into the sauce.