What are the environmental benefits and issues related to geothermal energy?

Geothermal energy is reliable

Geothermal energy is renewable

Geothermal energy produces minimal air emissions

Geothermal energy can help reduce global warming

Geothermal energy can offset other environmental impacts

Geothermal energy is combustion free

Geothermal energy minimally impacts land

Geothermal energy is a quiet technology

Geothermal energy conserves freshwater resources

Geothermal energy is competitive with other energy technologies

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Geothermal energy is reliable. Because geothermal resources are available 24 hours a day regardless of changing weather, geothermal energy is as reliable as any fossil fuel facility. Geothermal is a renewable energy technology that can offer baseload or intermediate power, is dispatchable, and can achieve high capacity factors. Geothermal represents a plentiful resource that has not been utilized to its full potential. As an additional bonus, geothermal energy does not rely upon energy imports. Geothermal is an indigenous source of energy.

Geothermal energy is renewable. Geothermal resources are sustainable because of the heat from the earth and water injection, and thus will not diminish like fossil fuel reserves. As time progresses and technology improves, our ability to extract geothermal resources with ease will increase, not decrease.

Geothermal energy produces minimal air emissions and offsets the high air emissions of fossil fuel-fired power plants. Emissions of nitrous oxide, hydrogen sulfide, sulfur dioxide, particulate matter, and carbon dioxide are extremely low, especially when compared to fossil fuel emissions. The binary geothermal plant, which currently represents around 15 percent of all geothermal plant capacity, along with the flash/binary plant, produce nearly zero air emissions. Lake County, California, downwind of The Geysers, has met all federal and state ambient air quality standards for seventeen years. At The Geysers, air quality has even improved as a result of geothermal development because hydrogen sulfide, which would ordinarily be released naturally into the atmosphere by hot springs and fumaroles, instead now passes through an abatement system that reduces hydrogen sulfide emissions by 99.9 percent.

The table below shows emissions from geothermal facilities compared with coal facilities.

* While geothermal plants do not emit sulfur dioxide directly, once hydrogen sulfide is released as a gas into the atmosphere, it eventually changes into sulfur dioxide and sulfuric acid. Therefore, any sulfur dioxide emissions associated with geothermal energy derive from hydrogen sulfide emissions.

Geothermal energy can help reduce global warming. Geothermal power plants emit very low levels of one of the most significant gases known to induce global warming: carbon dioxide. According to the Energy Information Administration (EIA), carbon dioxide accounts for 83 percent of U.S. greenhouse gas emissions. (1) Experts generally agree that global warming poses significant environmental and health impacts, including flood risks, glacial melting problems, forest fires, increases in sea level, and loss of biodiversity.(2) Geothermal power plants emit only a small fraction of the carbon dioxide emitted by traditional power plants on a per-megawatt hour basis, and can help reduce the overall release of carbon dioxide into the atmosphere.

Geothermal energy can offset other environmental impacts. Wastewater that would otherwise damage surface waters is being used to recharge The Geysers geothermal system and irrigate local land. In addition, electricity generation from geothermal resources eliminates the mining, processing and transporting required for electricity generation from fossil fuel resources. Finally, research into the extraction of minerals from geothermal fluids is showing great promise. Use of extraction technology would allow for the production of minerals without the environmental impacts of mining.

Geothermal energy is combustion free. Unlike fossil fuel power plants, no smoke is emitted from geothermal power plants, because no burning takes place: only steam is emitted from geothermal facilities.

Geothermal energy minimally impacts land. According to the U.S. Department of Energy, geothermal energy uses less land than other energy sources, both fossil fuel and renewable. No transportation of geothermal resources is necessary, because the resource is tapped directly at its source. Over 30 years, the period of time commonly used to compare the life cycle impacts from different power sources, a geothermal facility uses 404 square meters of land per gigawatt hour, while a coal facility uses 3632 square meters per gigawatt hour.

Geothermal energy is a quiet technology. Normal geothermal power plant operation typically produces less noise than the equivalent produced “near leaves rustling from breeze,” according to common sound level standards, and thus is not considered an issue of concern.

Geothermal energy conserves freshwater resources. Geothermal plants use 5 gallons of freshwater per megawatt hour, while binary air-cooled plants use no fresh water. This compares with 361 gallons per megawatt hour used by natural gas facilities.
Geothermal energy can reduce health impacts and healthcare costs. A recent analysis by Abt Associates (PDF) assesses the health impacts related to power plant emissions. Reducing power plant nitrogen emissions by one million tons and sulfur emissions by four million tons as of 2010 would mean:

• The number of related deaths would be reduced by 8714, with an associated healthcare savings of almost 53 million
• The number of related cases of chronic bronchitis would be reduced by 5997, with an associated healthcare savings of almost 2 million
• The number of related heart attacks would be reduced by 13,924, with an associated healthcare savings of almost 2 million

Because geothermal use offsets emissions of nitrogen and sulfur produced by fossil fuel power plant, geothermal can help reduce the healthcare effects and related costs.

Geothermal energy is competitive with other energy technologies when environmental costs are considered. A 1995 study estimates that costs of power generation would increase 17 percent for natural gas and 25 percent for coal if environmental costs were included.(3) These costs include land degradation, emissions of toxic chemicals and emissions, forced extinction and destruction of animals and plants, and health impacts to humans .

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(1) EIA. U.S. DOE (2003). Emissions of Greenhouse Gases in the United States 2003. figure ES1. Retrieved March 15, 2005 , from http://www.eia.doe.gov/oiaf/1605/ggrpt/executive_summary.html.
(2) IPCC Third Assessment Report: Climate Change 2001.Stand-alone edition
Watson, R.T. and the Core Writing Team (Eds.) IPCC, Geneva, Switzerland. pp 184 http://www.ipcc.ch/pub/un/syreng/spm.pdf
(3) Haberle and Flynn (1995). Comparative Economics and Benefits of Electricity Produced from Geothermal Resources in the State of Nevada. Univ. of Nevada, Las Vegas.