Here is one of twelve collages on The Permaculture Principles and how they might be applied, especially in the maritime Pacific Northwest. Concepts from David Holmgren's Essence of Permaculture.
"Use edges and value the marginal."
2. Stuff your Excelsior or Excalibur or solar dehydrator with them.
3. When they're brittle, fish them out and strip dry matter from midribs. Clean up and crumble to desired consistency. To make powder, run the crumbled greens in a dry blender.
4. Dry can (bake) in jars and open to use as needed. Good for up to five years in our experience.
Kale, collards, chard, beets, spinach, cabbage, broccoli, cauliflower, dandelions, false dandelions, lamb's quarters, turnip, kohlrabi, lettuce, and tatsoi, along with herbs to taste can all be included in this.
Use in breads, soups, frittatas, quiches, on meats, on potatoes, in eggs, power drinks, hot cereals, salads, wilted salads, stir fries, etc. Also can add to feeds such as poultry feeds. If you've hung onto it too long (eight years, say), there is always the compost
Caveat: spinach and amaranths contain a lot of oxalic acid and so some should not consume them in quantity.