Does Geothermal Energy Cause Pollution? Environmental Impacts of Geothermal Energy

does geothermal energy cause pollution

Does geothermal energy produce pollution despite being a renewable resource? Please read on for an explanation of this query.

When compared to fossil fuel power plants, geothermal energy has a very low environmental impact. Geothermal power plants can be a dependable source of renewable and environmentally friendly electricity when they are carefully sited and built.

Geothermal energy is largely untapped on a global scale. Since geothermal energy can be produced without burning fossil fuels, experts believe that geothermal plants are more environmentally friendly than fossil fuel power plants.

Continue reading as we look at how geothermal energy affects the environment.

Does Geothermal Energy Cause Pollution?

Geothermal energy’s effects on the environment depend on how it is used or transformed into usable energy. Nearly no environmental harm is caused by direct-use applications or geothermal heat pumps.

By reducing the use of energy sources that might harm the environment, they can even have a positive impact.

Water Quality and Use

Both the quality and use of water may be affected by geothermal power plants. High concentrations of sulfur, salt, and other minerals are frequently found in the hot water extracted from underground reservoirs.

does geothermal energy cause pollution

The majority of geothermal facilities use closed-loop water systems, whereby extracted water is pumped back into the geothermal reservoir after being used to generate heat or electricity.

In such systems, the water is kept inside steel well casings that are cement-fixed to the rock around them. In the United States, there have been no cases of geothermal site water contamination that have been publicly reported.

Additionally, geothermal plants use water for cooling and reinjection. Wet-recirculating technology combined with cooling towers is used in all U.S. geothermal power plants. Geothermal plants may need between 1,700 and 4,000 gallons of water per megawatt-hour, depending on the cooling method employed.

Most geothermal plants can, however, cool themselves using either geothermal fluid or freshwater; using geothermal fluids instead of freshwater clearly reduces the plant’s overall water impact.

Air Emissions

Regarding air emissions, it’s critical to understand the difference between open- and closed-loop systems. The amount of air emissions is minimal in closed-loop systems because gases extracted from the well are not released into the atmosphere and are instead returned to the ground after releasing heat.

Comparatively, open-loop systems release carbon dioxide, ammonia, methane, boron, hydrogen sulfide, and water vapor. Hydrogen sulfide, which has a distinctive “rotten egg” smell, is the most common emission.

Sulfur dioxide (SO2) is produced when hydrogen sulfide undergoes a change in the atmosphere. Due to this, tiny acidic particles are produced, which can damage the heart and lungs when ingested and absorbed into the bloodstream.

In addition to harming crops, forests, and soils, sulfur dioxide also contributes to acid rain, which also causes the acidification of lakes and streams. The biggest source of SO2 in the country, coal plants, have SO2 emissions that are about 30 times lower per megawatt-hour than those from geothermal power plants.

Mercury emissions from some geothermal plants must be reduced using mercury filter technology.

Scrubbers are capable of lowering air emissions, but they also create a watery sludge that is made up of the materials they have captured, including arsenic, mercury, nickel, vanadium, silica compounds, chlorides, and other heavy metals. Hazardous waste sites frequently have to be used to dispose of this toxic sludge.

Land Use

The amount of land needed for a geothermal plant varies depending on the characteristics of the resource reservoir, the amount of power capacity, the type of energy conversion system, the type of cooling system, the configuration of wells and piping systems, and the needs for a substation and auxiliary buildings.

does geothermal energy cause pollution

The Geysers, which is the biggest geothermal plant in the world, has a capacity of about 1,517 megawatts and a surface area of about 78 square kilometers, or about 13 acres per megawatt.

Many geothermal sites are situated in remote and delicate ecological regions, similar to the Geysers, so project developers must take this into consideration when planning their projects.

The removal of water from geothermal reservoirs can occasionally result in land subsidence, a phenomenon where the land surface sinks. The majority of geothermal facilities minimize this risk by reinjecting wastewater into reservoirs after the heat of the water has been extracted.

Hydrothermal plants are sited on geological “hot spots,” which tend to have higher levels of earthquake risk. There is proof that hydrothermal plants can increase the frequency of earthquakes. Small earthquake risk can also rise with improved geothermal systems (hot dry rock).

Similar to the technique used in hydraulic fracturing for natural gas, this procedure involves pumping water at high pressures to fracture underground hot rock reservoirs. By placing plants at an appropriate distance from significant fault lines, the earthquake risk associated with enhanced geothermal systems can be reduced.

When a geothermal system is located close to a densely populated area, ongoing monitoring and open dialogue with the surrounding communities are also essential.

Life-cycle Global Warming Emissions

In open-loop geothermal systems, methane, a more potent global warming gas, makes up a smaller portion of air emissions than carbon dioxide, which makes up about 10% of air emissions.

The estimated global warming emissions for open-loop systems are 0.1 pounds of carbon dioxide equivalent per kilowatt-hour. These gases aren’t released into the atmosphere in closed-loop systems, but there are still some emissions related to building the plant and the surrounding infrastructure.

The life-cycle global warming emissions of enhanced geothermal systems, which require energy to drill and pump water into hot rock reservoirs, are roughly 0.2 pounds of carbon dioxide equivalent per kilowatt-hour.

To put this in perspective, estimates of life-cycle global warming emissions for electricity produced by coal range between 1.4 and 3.6 pounds of carbon dioxide equivalent per kilowatt-hour, and those for electricity produced by the natural gas range between 0.6 and 2 pounds of carbon dioxide equivalent per kilowatt-hour.

Environmental Downsides to Geothermal Energy

does geothermal energy cause pollution

There are environmental drawbacks associated with geothermal energy, as there are with the majority of conventional and renewable energy sources.

One of the main issues with geothermal development and the building of power plants is land subsidence. Over time, the land starts to sink as plants draw water and steam from underground reservoirs, changing the vegetation and wildlife.

To mitigate this, the majority of geothermal plants reintroduce geothermal waters into the ground. Location affects the availability of geothermal energy. This entails constructing geothermal power plants close to energy sources.

The increased likelihood of small earthquakes is yet another environmental drawback of geothermal energy. Earthquakes may become more likely if exploratory wells are drilled near fault lines to look for geothermal potential.

Drilling at geothermal plants results in the release of greenhouse gases like hydrogen sulfide. However, compared to fossil fuels, these gases emit fewer greenhouse gases.

For geothermal energy to be developed sustainably, the process needs to be managed properly.


Geothermal power plants have a long lifespan and can even last for centuries with proper management. Geothermal energy is always available and independent of elements that affect the weather, such as the sun and wind.

Increased earthquakes are another issue that may occur while geothermal power plants are in operation. Geothermal power plants are usually located near fault zones or geological “hot spots” that are especially prone to instability and earthquakes, and drilling deep into the earth and removing water and steam can sometimes trigger small earthquakes.

Fortunately, energy providers can address these issues in a more environmentally friendly way.


How Much Pollution Does Geothermal Energy Cause?

Geothermal power plants emit 97% less acid rain-causing sulfur compounds and about 99% less carbon dioxide than fossil fuel power plants of similar size.

Does Geothermal Energy Cause Global Warming?

Unlike fossil fuels, geothermal energy is a renewable resource that does not emit greenhouse gases that cause climate change.

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