Always feed a variety of greens to animals that require it in their diet, whether exclusively or partially. The reason for the variety isn't because the reptile cares to get variety, but because it is the best way to ensure they are getting all the nutrients they need and to also prevent reptiles from being picky.
The way I usually store greens it is wash it all, then pat dry with paper towel. Then I layer paper towel, leaves (of whatever green), paper towel etc. Then I store in either large zip lock bags, or tupperware type containers. This seems to keep the greens for several weeks in the fridge, but this varies with each green. The more 'rubbery' greens (collard greens, kale etc) tend to last longer, though often they do start to wilt towards the end of the second week, but it really varies. Dandelion greens, endive and sometimes escrole can start to rot soonest, mostly due to how difficult it is to get alot of the water off the leaves.
One way to avoid green waste is to make a salad for yourself. Everything that goes into a bearded dragon's salad (minus pellets and vitamin powders of course) you can eat. Alot of the 'exotic' greens are used in 'spring mix' (though t his often has alot of leaf lettace and baby spinach in it as well, which isn't good to feed bearded dragons). SOme are a bit bitter but when all mixed together with a light salad dressing, they are quite good and flavorable.
Or, like the other poster, you can get yourself a couple of guinea pigs and feed them teh excess. They certainly love greens and are interesting pets as well, if you can stand an animal that is active a good 20 hours or more a day, guinea pigs don't really sleep, except for very short 5-15 minute 'naps'). They make great lap pets as well, being a decent size to hold, easy to acclimate to being held (gently and securely of course) and do make rather pleasing noises when content. If you do decide to get some, they are best in groups of two or more (unless you want alot of baby guinea pigs, get all females, or, if you get a young pair of 'brothers' they may tolerate eachother throughout their lives without fighting. Make sure you know how to sex them as many petstores can't seem to sex guineau pigs properly, often housing males and females together and since guinea pigs can get pregnant quite young (as young as 4 weeks, if I recall correctly) it is always possible a petstore bought pig could be pregnant. Fortunately they don't have huge litters (2-3 being average with 4-5 being uncommon to rare) and the babies are fully furred and have eyes open, it is an interesting experience to see born. But since this is a bearded dragon forum, won't get into extensive details about guinea pigs.
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PHLdyPayne