I do my best to recycle...and I've put the word out to family/friends that as they buy cherry tomatos or fruit in those little green baskets, to please save them for me.
I plan on filling them with wetted sphagnum moss: the longer stuff on the sides and the broken down material for the filler. I'd use them for lettuce, radishes, etc...maybe mini-carrots.
You might find that moss by itself is too wet and easily compresses (not allowing enough air which causes rot). It also breaks down fairly quickly and is not considered renewable.
Depending on the type of system you use, I suggest a mixture of (moss if you have to), perlite/ vermiculite and coco coir. Again, depending on type of system, these planters might be too big or small for what you want. You might also consider using sand as your medium if you wantto grow carrots.
Thanks Carey...definitely something to think about. My options are certainly still in the planning stages, so this is good to know.