Here’s a no-brainer for you: when you chop up your leeks, keep the lower section (about 1.5 cm) with the roots intact. Put the roots into water for a day or so, and then plant them back into your vegie patch. After a few weeks, new leaves will sprout, which you can harvest.
Growing your own produce saves money and reduces your carbon footprint (no transport and refridgeration required). When you grow your own, you know it’s organic, and there is less waste, because you only pick what you need.