PP I have the type you are looking at. It's not as big as a wheelie bin (3ft tall at the most). I empty it by tipping the contents onto a plastic tarp and putting what was on the top and not composted yet back into the bin. Spread the rest out on the tarp then cover an area with wet newspaper for a couple of hours and all the worms migrate to the cool and dark under the paper to be out back into the bin.

Not sure of the advantages of the COW system but mine works ok and needs emptying only one a year. Lots of liquid feed from it which is diluted 1 part to 10 water and goes on everything.

The DIY one is not difficult and is the COW pattern but with a cost of about £11 (plus worms) if you have a B&Q and Poundstretcher near you.

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Digger-07

"If you think you can, or think you can't, you're right" Henry Ford.