It’s just another way of processing food scrap and yard waste.
You don’t need to do anything special for raised beds if you want to have a ton of worms in them, except mulch the tops of the beds every spring and fall,.and occasionally dig a hole and dump in a bunch of uncomposted food waste. Add layers of straw, wood mulch, lawn clippings, whatever, leaf mulch. Worms will devour everything you put on it and turn it to castings.
Read up on windrow vermicomposting to get an idea of how the worms will literally just work their way down a row of food converting all of it to castings. Some people keep worms just in a heap in the middle of the yard, with nothing special except maybe covering with clear plastic over winter. The worm population will wax and wane based on how much food they have, and as long as the food and substrate doesn’t completely dry out.
I don’t think you should take up raised bed space to put in any kind of composting system unless you absolutely don’t have another place to compost. Kind of wastes the advantage of having raised beds if you’re not using them for your crops. I’d also suggest starting small, and scaling up after some experience.
As the worms munch, the food they eat goes through them and gets broken down. The worms are home to all sorts of good bacteria that help with breaking things down. That’s the idea, break things down so plants can use them, kind of like prechewing their food for them. I’m no expert. I ordered my worms online from Uncle Jim’s Worm Farm and they also have a ton of information on their site to help you get it going.
I sort of gave up on keeping worms after a few years. I just used a bin half buried in the ground. And every so often I would spread some of the worms around to the different garden beds on my property, or when I planted something new, or started a new compost bin or compost heap or whatever. They’re everywhere now, no point in raising them. All the beds are aerated, tilled, and plants growing well. That’s really what the worms and worm castings are for, is enriching the soil. Once your soil is good, if new waste accumulates, the worms that are there take care of it.
Like you can buy worm castings at the store as a soil additive, but if you already have good soil you would not buy worm castings to use just as fertilizer, you’d just buy whatever fertilizer you like. I guess worms are really best for conditioning soil. Part of the thing with raised beds is that you filled them! So they shouldn’t need soil conditioning unless they’ve been abandoned for a long time or if there’s been no crop rotation for a long time.
Really no downsides as far as I can think of, other than the time and effort of making sure they are fed and have enough water (if you’re using a mostly sealed bin as I was). Too much water is as bad as not enough. When it rains and you see worms come out, it’s not because they like the water and want to drink, it’s because their house is flooded and they don’t want to drown.
I don’t know, that’s some insight. Feel free to ask some specific questions.
