We recently wrote an ezine article on the benefits of using discarded old car tires (UK spelling tyres) to make a practical worm farm that costs virtually nothing to construct. See our article at –
http://ezinearticles.com/?Stacked-Tire-Worm-Farm&id=2020501 .
There is more information on this highly economical ststem from Working-Worms at the following location –
https://working-worms.com/content/view/39/61/
Steve