Why build a worm bin? Why can't you have a worm heap?

Question

I understand the value of vermiculture, and grew up with a wormbox on the back patio that made beautiful castings. What I don't understand is the purpose of the bin.

If I kept a heap of worm-friendly scraps, mixed with some dirt and kept moist, and covered with a layer of dirt to keep pests away, wouldn't that accomplish basically the same thing as a worm bin?

In other words, wouldn't a poorly run compost heap that doesn't get hot basically turn into a worm heap anyway, no need for a bin?

I feel like I might be missing something important, but a heap is a lot cheaper and simpler than a bin, and wouldn't dry out as quickly or have as much susceptibility to temperature swings, and wouldn't rot and need replacing every few years.

Answer 1

Basically you are right. The processes in a compost heap are a bit more complex than in a worm bin, because worms should be a part of a (only warm, not hot) compost heap among other, way smaller microorganisms.

The main advantages of worm bins are that they are way smaller and fit easily even on a balcony and that the worms inside (and you have a much larger worms to organic matter ratio) are better protected.

Do not underestimate the number of predators that would love to snack on your precious worms, though. I've watched backbirds in my backyard dig fist-sized and larger holes in loose material on our compost heap and depending on the wildlife in your area you might be surprised who stops by. A badger won't hesitate turning your heap upside down, but there are a few smaller wormlovers like moles that shouldn't be overlooked either. Of course a reasonably stable worm poplation in your compost will recover and if your compost sits on bare soil, it will "fill up" again from below.