Rocket Stove Mass Heater. "heat your home with 80% to 90% less wood; exhaust is nearly pure steam and CO2 (a little smoke at the beginning); the heat from one fire can last for days; you can build one in a day and half; folks have built them spending less than $20"
Instead of burning wood for heat, some Europeans now build a compost pile over plastic water lines that extract heat from the decomposing plant material. Temperatures can get as high as 149 degrees. With a circulating pump as the only moving part, the compost heater lasts an average of 12 to 16 mos. – and occasionally up to 24 mos. – providing heat and up to 80 percent of the hot water for a 1,500 sq. ft. home.