I am not a scientist, but I believe big agri-bussiness does not want worms around because.... they can NOT make money off them! If worm castings were widely used the there would be little need to purchase fertilizers and many other farm chemicals. My opinion.

I have 3 outdoor worm beds. They are easy to operate.

My original bin is 5'x3'x18",is made of re-recycled
4"x6" redwood posts, has a plywood top and NO bottom. Line the bottom to keep out moles and gophers.Your worms will not leave unless you don't feed them.No problems with over-feeding or too much moisture.

My other 2 beds are large windrow type systems for horse manure.

Unless you have very hot or very cold climate, outside wormin is easy..

Hope this helps and good luck

I say i dumped maybe 25 worms in my in ground garden about 6 months ago. We had an uncommon summer rain here last week. I say about 100 worms were on the surface after the rain. No more fruit flies in my house.

I have my bin outside and it works great. I really can't comment on the invasive species dilemma besides if you have been putting your worm compost in your garden without deliberately sterilizing it first, you have already been introducing them.

Outdoor bins are very low maintenance, but most of the reason for that is that they have to be very large in order to always have some locations inside them where the worms will find the right temperature and moisture. Since you are in GA, you won't have so much trouble with frost but you still want to keep the sun off of it and have enough thickness that it can't dry all the way out if you go on vacation.

3'x5' is a good dimension, and I would try to make the bin 3' tall with the goal of keeping at least 2' of material in it.