I had some damaged double walled GH plastic & used it for a compost bin.
2X4 frame stuck in the ground 4". It is 4' X 6' & 4' high.
I sheeted the outside of the East & South walls with the GH plastic.
North side is plywood.
Inside, I put old carpeting on the floor, cut some holes for the earth worms.
I stapled some Geo fabric to the inside 3 side walls.
I made a 2 section, insulated, solar heated, removable door for the front same
as the E & S walls.
At the end of garden season, everything thats not edible, from the garden & green house goes in it in layers. a layer of grass clipping & leaves, garden stuff, layer of leaves/grass etc. I add some air vent pipes vertical & horizontal.
When all the garden & GH are cleaned out, I top it with grass clipping & leaves as high as I can stack it.
It steams till about December. It thaws around mid April & is about 1/2 full.
The first time I mow grass, I empty it, mix in fresh grass clippings to get it cooking.
By August its "done" compost. I empty it into the "done" bin. & bag up what don't fit.
I now have next years spring compost ready to go. Few yards of "Garden Gold"