I am wondering if anyone knows of or has tried using any materials besides plastic to cover up compost piles with. The purpose is to retain moisture, especially on the top layer of the compost pile, which gets dried out too fast - so it needs to be some kind of solid piece of material that's fairly non-porous.
Depends how big your piles are. For mine I just use big sheets of cardboard. Once it's broken down enough, I just sort of tear it up with a shovel, let it mix into the pile, and put a new sheet on top. Works great for a small-ish pile, but it would definitely not be feasible on a larger scale.
I picked up a few pieces of leftover galvanized steel roofing a long time ago and have used them. They are very durable and keeping the sun or extreme tropical storm downpour from directly hitting the compost pile is really important for me. I know some people have issues with galvanized steel, so maybe baked enamel steel roofing sheets might be more appropriate. The kind I have is not standing seam, but corrugated. This means I can lay one down and then lay the next one on where I deem appropriate, and they just fit themselves together via gravity as long as you overlap them in a parallel fashion. Bricks along the edges have been sufficient for holding them down through tropical storm force winds.
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