When done properly, composting creates a great deal of heat – heat that can be harnessed to heat water and create usable energy. To capture this heat, the late French innovator, Jean Pain, developed a technique (Jean Pain Method) harvesting energy from composting materials, ultimately providing 100% of his household energy needs. He experimented with looping pipe throughout a compost pile and running water through it, as well as distilling methane to run a generator and use for cooking.
I visited Brian Kerkvliet, of Inspiration Farms in Washington, to see his version of a compost based bio-energy system. Brian used about 100 ft of 1/2 inch poly-pipe coils through the pile, looping them back and forth through each layer as they built the pile lasagna method. Cold and hot water pipes led to their outdoor shower where hot water started out at 160 degrees (thus the need to temper with cold water) and ended up heating to about 90 degrees by the end of two months. So for about 1 1/2 hours of labor (building the bed with the help of farm interns) they got two months of pretty unlimited hot showers. After the hot showers, he also had a lovely pile of compost and the moisture from the shower fed mushrooms … Hot water, compost and mushrooms … Permaculture!
Two of my other podcasts mention the Jean Pain technique: