Abstract: An underground reactor for creating hydrocarbons and chemicals from organic material can include a heat recovery device. Some embodiments of the present disclosure include at least one tube that injects biomass underground and at least one second tube that collects reacted biomass on the surface. Further tubes are also disclosed for the ability to control temperature and pressure and collect minerals and carbon dioxide. In another embodiment, a super-critical fluid is injected into the underground reactor. Methods for utilizing the reactor are additionally provided. Further embodiments include methods of using the reactor such as, for example, methods of creating fuel from algae and methods of using the minerals and carbon dioxide as food for an algae farm that will be used as biomass for the reactor.