compost pile water heater

[c-ray]

I was just thinking about a fellow who was telling me that he would build big compost piles in some sort of fence like 6 or 7 feet tall and before he would fill it up he would run some copper pipe through the center of the pile and the water would come out very hot

I think he was using the flexible copper pipe and making a coil in the center

also I was reading a fellow who said he was heating a greenhouse by running pipes on the greenhouse floor and circulating the water in these pipes through the compost pile with a pump