As far as I know, you basically use straw or hay bales instead of wood for making the walls of your raised beds. Very simple, but doesn't work in this climate because they dry out too fast. It would also take alot of fill dirt to bring them up to level. In a wet environment, it would be a great idea. If you are in a cold area, though, you could use bales for the beds, fill them about half full, and cover over with thick clear plastic or glass to make minii-greenhouses for winter crops.
Mrs H

I make hotbeds with straw bales (actually mine are hay). I fill them 3/4 full with fresh horse manure and then top them up with dirt. I have a heat activated window opener on mine that opens or closes the plastic lid as needed. It's the only way I can get melons to ripen in my clay soil and climate zone.

Mrs H is correct about them drying out. Mine don't because it's humid here. Tomatoes and squashes will send down their roots to three or four feet deep, so they find water fairly easily, if you're growing lettuce you will need to water often.

They will shrink and separate some. I put a racheting tie-down around mine so I can tighten it as it shrinks

interesting

Hi, soaplady. I have a friend in Farmington MO who has set up "raised beds" in her hoop house using straw bales. She places two side by side, then puts on a layer of manure which she waters in well. As the straw starts to compost, she puts on a layer of potting mix and plants seeds for her winter salad greens and such in the potting mix. The heat from the composting straw helps germination but doesn't last long enough to provide any heat during the growth period.

I read a post from a man in Florida on either the Market Gardener thread or Four Season Harvest who does the same thing outdoors with his lettuces in his cool season. He put the bales cut edges down on pallets and used a weed eater tool to carve out a depression in the bales. I think he used mushroom compost as a growing medium. He said he sells his greens for $6/# wholesale or $8/# retail.

Last summer I put a single straw bale, cut edge down in the yard. I put dried goat manure on it, watered it in and transplanted a volunteer pumpkin seedling into it--just opened a space in the cut ends and watered it. I emptied the chickens' waterer onto it every day when I gave them fresh water. It was a miniature pumpkin and produced a few fruits. The added benefit is that the whole bale composted nicely. The best thing is that all summer long, I didn't see one cucumber beetle on the vine or any other bug for that matter.

Since I have livestock, I have used leftover or spoiled hay with pretty good results. The trick since hay can have a lot of seeds is to water it well, let the seeds germinate then cover the whole business for a few days with clear plastic to "cook" the bale and seeds.

Yesterday (Oct 19) I put "books" of hay treated this way to make an experimental bed in the second hoop house, wet them down and put some good finished compost over the top. We'll put the cover on the hoop house this afternoon and then I can start transplanting my seedlings into the beds. The other two beds are finished compost and plain soil just in case the straw/compost bed isn't as effective. I am concerned about the layers freezing where the natural soil hasn't done so in the past, even in extended periods of cold. At least our cold here in central Missouri.

Hey, I'm a Master Gardener too and make soap as well. Also, cheese from our goats' milk, have the chickens, big gardens (about 5000 sq. ft.), orchard, etc.