9 Environmental Impacts of Geothermal Energy

It’s going to be an exciting ride on the environmental impacts of geothermal energy.

Geothermal energy is heat contained below the earth’s surface. It is a renewable and clean source of power that has gained traction in recent years as more and more people look for sustainable alternatives to traditional energy sources.

This type of energy is derived from the natural heat found beneath the Earth’s surface, and it can be used to generate electricity and heating. No fossil fuel needs to be burned to generate geothermal power, and as long as the earth exists (likely for another 4 billion years), we won’t run out of geothermal energy.

Geothermal energy generation isn’t limitless, in as much as there are a limited number of suitable locations on Earth for geothermal power plants.

While geothermal energy has many advantages, such as being clean and a renewable resource, it also comes with some environmental impacts.

The environmental impact of geothermal energy is minimal, especially compared to fossil fuel power plants. When sited and constructed carefully, geothermal power plants can be reliable sources of renewable and environmentally friendly electricity.

In this article, we will explore the environmental impacts of geothermal energy that answer the question of whether this form of energy production is truly green so that you can make an informed decision when considering potential sources of power.

9 Environmental Impacts of Geothermal Energy

The fact that Geothermal energy is a renewable source of energy that can be used to generate electricity and provide heating, cooling, and hot water does not negate its possible impacts on the environment.

Just like with any other type of energy production, there are environmental impacts associated with geothermal energy which we have discussed below.

• Impact on Water Quality and Use
• Air Pollution
• Land Use
• Land Subsidence
• Global Warming
• Increased Earthquakes
• Disruption of Local System
• Impact on Fish and Wildlife
• Reduces Pollutants

1. Impact on Water Quality and Use

Geothermal power plants can have impacts on both water quality and consumption. Hot water pumped from underground reservoirs often contains high levels of sulfur, salt, and other minerals.

Water is used by geothermal plants for cooling and re-injection. Depending on the cooling technology used, geothermal plants can require between 1,700 and 4,000 gallons of water per megawatt-hour.

However, most geothermal plants can use either geothermal fluid or freshwater for cooling; the use of geothermal fluids rather than freshwater reduces the plant’s overall water impact.

On the other hand, most geothermal plants re-inject water into the reservoir after it has been used to prevent contamination. In most cases, not all water removed from the reservoir is re-injected because some is lost as steam.

Therefore, to maintain a constant volume of water in the reservoir, outside water must be used. The amount of water needed depends on the size of the plant and the technology used; however, because reservoir water is “dirty,” it is often not necessary to use clean water for this purpose.

For example, the Geysers geothermal site in California injects non-potable treated wastewater into its geothermal reservoir.

2. Air Pollution

Air pollution is a major issue in geothermal energy, both in open- and closed-loop systems. In closed-loop systems, gases removed from the well are not exposed to the atmosphere and are injected back into the ground after giving up their heat, so air emissions are minimal.

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

 Once in the atmosphere, hydrogen sulfide changes into sulfur dioxide (SO₂). This contributes to the formation of small acidic particulates that can be absorbed by the bloodstream and cause heart and lung disease.

Sulfur dioxide also causes acid rain, which damages crops, forests, and soils, and acidifies lakes and streams. However, SO2 emissions from geothermal plants are approximately 30 times lower per megawatt-hour than from coal plants, which is the largest source of sulfur dioxide emissions.

Some geothermal plants also produce small amounts of mercury emissions, which must be mitigated using mercury filter technology.

Scrubbers can reduce air emissions, but they produce a watery sludge composed of captured materials, including sulfur, vanadium, silica compounds, chlorides, arsenic, mercury, nickel, and other heavy metals. This toxic sludge often must be disposed of at hazardous waste sites.

These emissions contribute to air pollution which could cause health issues for nearby communities if not properly managed.

3. Land Use

Though the amount of land needed for the construction of a geothermal plant varies, there is a huge amount of land needed to build the facility due to the properties of the resource reservoir, the amount of power capacity, the type of energy conversion system, the type of cooling system, the arrangement of wells and piping systems, and the substation and auxiliary building needs.

This has led to a large loss of habitat for species and a whole lot of habitat fragmentation, which leaves species vulnerable and, to some extent, a loss of biodiversity.

The Geysers, the largest geothermal plant in the world, has a capacity of approximately 1,517 megawatts and the area of the plant is approximately 78 square kilometers, which translates to approximately 13 acres per megawatt.

Like the Geysers, many geothermal sites are located in remote and sensitive ecological areas, so project developers must take this into account in their planning processes.

4. Land Subsidence

This is a situation in which the land surface sinks; it is also known as surface instability, which is a major environmental concern that comes from geothermal plants.

This sometimes occurs as a result of the removal of water from geothermal reservoirs within the earth, the land above those reservoirs can sometimes sink slowly over time.

Most geothermal facilities address this risk by re-injecting wastewater back into geothermal reservoirs after the water’s heat has been captured.  This goes a long way to reduce the risk of land subsidence.

5. Global Warming

In geothermal systems, approximately 10%  of the air emissions are carbon dioxide, and a smaller amount of emissions are methane, a more potent global warming gas. Estimates of global warming emissions for open-loop systems are approximately 0.1 pounds of carbon dioxide equivalent per kilowatt-hour.

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

6. Increased Earthquakes

Earthquake is an additional problem that can arise during the operation of geothermal power plants. 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.

Also, enhanced geothermal systems (hot, dry rock) can increase the risk of small earthquakes. In this process, water is pumped at high pressures to fracture underground hot rock reservoirs, similar to the technology used in natural gas hydraulic fracturing.

There is also evidence that hydrothermal plants can lead to an even greater earthquake frequency. Earthquake risk associated with enhanced geothermal systems can be minimized by siting plants an appropriate distance away from major fault lines.

When a geothermal system is situated near a heavily populated area, constant monitoring and transparent communication with local communities are also necessary.

7. Disruption of Local System

The extraction process of geothermal resources, which involves tapping into geothermal resources, can disrupt local ecosystems and habitats.

This is seen through the release of gases such as nitrogen oxides, carbon dioxide, sulfur dioxide, and hydrogen sulfide, as well as the deforestation of areas to build the plant facility.

8. Impact on Fish and Wildlife

As earlier discussed above, air and water pollution are two leading environmental challenges associated with geothermal energy technologies. The major concerns are the safe disposal of hazardous waste, siting, and land subsidence.

A large amount of water is required by most geothermal plants for cooling or other purposes.  Which could affect other uses of water, such as fish spawning and rearing in areas where water is in short supply.

Hydrogen sulfide, ammonia, methane, and carbon dioxide may be contained in the steam vented from the surface.

Solids that are dissolved and discharged from geothermal systems include sulfur, chlorides, silica compounds, vanadium, arsenic, mercury, nickel, and other toxic heavy metals that can be deleterious to localized fish and wildlife if they are released in their concentrated form.

Geothermal resource development is often highly centralized, so reducing their environmental impacts to an acceptable level is achievable.

9. Reduces Pollutants

The primary benefit of geothermal energy is that the power plants do not emit much carbon dioxide or sulfur oxides into the atmosphere like traditional fossil fuel-burning power plants.

This makes geothermal energy a clean source of electricity without any overhead costs associated with mitigating air pollution from CO₂ and other pollutants created through combustion processes. Geothermal power plants produce fewer air pollutants or greenhouse gas emissions because they don’t rely on burning fuel.

Conclusion

Geothermal energy, known as a green source of energy, has also been proven to have negative and positive impacts on the environment. Therefore, we must take appropriate consideration of anything we do in the environment, even the ones we assume to be environmentally friendly.

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