Shawn Jadrnicek wrote:...Similar to the Agrilab system, the compost pile is placed on top of an insulated slab. Instead of using fans to extract hot vapor, water flowing through pipes inside the slab extract heat from the compost pile. Additional techniques embed pipes inside compost piles. The pipes are strategically placed to intercept hot vapor rising from natural ventilation processes inside the pile...
Shawn Jadrnicek wrote:I go into all the details in the book but the concrete slab has about 900 feet of 3/4 inch pex pipe inside and gets around 15,000 btu's/hr when the compost is in the 150's. We've also run 1" pex through the middle of a windrow style pile and get around 4-6,000 btu's/hr from a single run down a 35 foot long 40 cubic yard pile and around 8,000 btu's/hr from two runs. Depending on flow rate of water and amount of pipes you can extract too much heat and cause compost temps to drop. Heat transfer is also dependent on moisture levels in compost pile.
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