The energy sources is so large that the rate of depletion by a geothermal energy extraction project is negligible. Projects based on using the remnant heat stored in shallowly placed igneous rocks may be non renewable. However, the use of energy from such sources does not produce greenhouse gases. Another renewable resource, tidal power results from a harnessing tidal currents which are caused mainly by the gravitational pull of the moon on the oceans as it circles the earth. When fossil fuels are burnt to release energy, they also release carbon dioxide to the atmosphere.
Carbon dioxide is the main greenhouse gas that contributes to global warming.
Biomass is the only renewable energy source that releases carbon dioxide in use. However the carbon dioxide emitted in use is balanced by the incorporation of carbon from the atmosphere into the biomass while the biomass is growing. If the biomass resource is being used sustainably, there are no net carbon emissions over the time frame of a cycle of biomass production. This could be a year for an agricultural crop wastes such as bagasse or decades for forest products. In addition minor amounts of greenhouse gases may be created in producing the technology to transform the renewable energy resource into useable energy.