Geothermal energy and the environment

Impact
Air Carbon dioxide and other emissions such as hydrogen sulphide (from geothermal power generation)
Water Saline water in some geothermal aquifers
Land use Soil subsidence (from geothermal power generation); land disturbance for drilling sites, power plants and transmission lines

Geothermal systems provide an environmentally benign source of energy.

According to Natural Resources Canada, ground-source heat pumps can reduce greenhouse gas emissions by more than two-thirds compared with combustion furnaces using fossil fuels. However, these comparisons of emissions depend on energy systems in a region.

Geothermal power plants take up little land area and do not produce wastes. But depending on the technology used, they may also have environmental impacts.

Geothermal power plants exploit hot, underground fluid, which consists of mostly steam and small amounts of carbon dioxide, hydrogen sulphide, methane and ammonia. The amounts of chemicals released when geothermal fields are tapped can be hazardous or objectionable to people living and working nearby.

In the United States, where geothermal power generation is increasing, governments have established requirements for the removal of hydrogen sulphide from geothermal emissions.

Drawing water from the ground for power generation may also cause rock formations at the site to compact, leading to land subsidence and settling.

Some “open loop” heat pump systems may affect aquatic ecosystems if they draw water from a water body and discharge warmer or cooler water back into the water body. Standards and regulations are intended to ensure that the water body is large enough to absorb the thermal load without affecting ecosystems adversely.