8.5 Geothermal, Biomass and Other Sources

Notes

• Geothermal energy uses heat from within Earth. Power plants tap hot water and steam; geothermal heat pumps use stable ground temperature to heat and cool buildings. Best near tectonic boundaries such as Iceland and parts of California. Limits: location dependent, can release trace gases.
• Biomass is energy from organic matter: wood, crop waste, and manure. Biofuels include ethanol (from corn or sugarcane) and biodiesel. Biomass is considered renewable and can be nearly carbon neutral if regrown, but it can compete with food crops, drive deforestation, and still produces air pollution when burned.
• Hydrogen is an energy carrier that produces only water when used in a fuel cell, but it must be produced using other energy (often from natural gas).
• Tidal and wave energy use ocean motion but are limited to certain coasts and are still expensive.
• Example: Iceland gets much of its electricity and heating from geothermal sources because it lies on a volcanic plate boundary.