Geothermal has significant value potential. It also has potential risk (whether to geologic stability, water supplies…) as indicated by seismic activity occurring in areas where geothermal drilling has taken place. The idea of taping sources such as warm bio mass storage areas (sewer systems) can be extended to any location that may have decaying biomass (landfill composting locations, sewer pipes, reclaiming steam pipe radiant heat or other). There may be a great deal of options through creative innovation. Geothermal System Taps Sewage Instead of Bedrock : TreeHugger.