Around the world, and more recently in the U.S., cities are realizing that the water leaving our homes and offices?specifically, warm and hot wastewater?is an astoundingly powerful source of energy. One estima te is that Americans flush 350 billion kilowatt-hours of energy into the se wers each year?roughly enough to power 30 million U.S. homes. Citie s are taking notice, and taking steps to install sewage heat recovery syste ms to get a piece of that energy resource.
Using existing technology developed for geothermal to do this. Clog free he at exchangers might get tricky dealing with raw sewage though.