oil in the proper equipment. Back when we used to dable with "alternative energy", that usually meant getting warm through manual labor, we ran a waste burner for heat. It was basically a big furnace, that heated water in pipes which then simultaneously circulated trhough the house in a low-presure system. We used to filter waste motor oil through rolls of tiolet paper, recycle it to the farm eqiumpent, then when we practically drained the farm equipment the next time we lightly bunred the oil. And eventually the toilet paper filters. made for some really cheap exponentially heat. & depleting the ozone layer trhough the use of fossil fuels.