Improved systems, methods, apparatus and compositions for generating, extracting and distributing the renewable heat energy produced by microbial decomposition of organic biomass within a contained and controlled environment. This heat energy is preferably transferred and distributed, preferably by the use of heat pipes, to the interior of a greenhouse or other structure to be heated, either directly or via heat exchange apparatus such as hot water heating systems. In one embodiment heat transfer and distribution mechanism customized to the application requirements of a greenhouse heating batch-type process is disclosed, along with a recipe for a readily available biomass material composition that will slowly decompose while it generates a substantial quantity of usable heat energy to be consumed in the elevation of temperature in a separated greenhouse basement confinement area. Additional continuous and batch process embodiments of biomass heating systems are also disclosed that extract heat energy from decomposing biomass for heating uses. In some embodiments gaseous products generated in a biological decomposition process, primarily CO.sub.2, are utilized to enhance plant growth in the greenhouse environment.