Does Geothermal Energy Affect Habitats?

Geothermal energy is a renewable energy source that harnesses heat from within the earth to generate electricity and provide heating and cooling (https://www.eia.gov/energyexplained/geothermal/). With growing concern over climate change and the environmental impacts of fossil fuels, understanding the impacts of renewable energy sources like geothermal is important. This article will examine how geothermal energy facilities and operations affect natural habitats. We will look at direct habitat disturbances from plant construction, indirect impacts from operations like water usage, and options for habitat restoration and conservation. The goal is to provide a thorough overview of geothermal energy’s effects on ecosystems to inform discussions around expanding this renewable resource.

Geothermal Energy Basics

Geothermal energy is heat energy generated and stored beneath the earth’s surface. It is considered a renewable energy source as the heat is continuously produced inside the earth (U.S. Department of Energy, n.d.). There are three main types of geothermal energy systems used to generate electricity:

• Hydrothermal systems, which tap into naturally occurring hydrothermal fluids in underground reservoirs (U.S. Department of Energy, n.d.).
• Enhanced geothermal systems (EGS), which inject water into hot dry rock reservoirs to create a geothermal reservoir (U.S. Department of Energy, n.d.).
• Geopressured systems which use hot water and natural gas under pressure (Union of Concerned Scientists, 2018).

To generate electricity, geothermal power plants use steam from these hot water reservoirs to drive turbine generators. The used steam and water are then returned back into the reservoir to be reheated and reused (U.S. Department of Energy, n.d.). In 2019, geothermal energy produced about 17 billion kilowatt-hours, meeting 0.4% of total U.S. utility-scale electricity generation (U.S. Energy Information Administration, 2020).

Geothermal Plant Construction

Constructing a geothermal power plant requires drilling wells to access the hot underground water or steam that will drive the turbines. This drilling process can disrupt habitats on the surface. Building access roads and well pads requires clearing vegetation and leveling land (Environmental Impacts of Geothermal Energy, 2013). According to the U.S. Department of Energy, a typical geothermal well pad occupies about 1-8 acres of land, with the drill rig itself taking up just a quarter-acre. However, access roads and pipelines may disturb larger areas.

The drilling process utilizes large, heavy machinery that can compact soil, increase erosion, and produce noise and vibration. The drilling fluids used to lubricate and cool the drill bits may contaminate soils. Proper containment and disposal of these drilling fluids is important to avoid groundwater pollution. Additionally, the underground fractures created by hydraulic fracturing during drilling for enhanced geothermal systems can induce small earthquakes (Geothermal energy and the environment, 2022).

Once the geothermal reservoir is accessed, materials must be brought in to construct the power plant facility itself. This involves further truck traffic, noise, and general disruption at the site. Plant facilities may directly replace or fragment sensitive habitats. Careful siting, minimal footprints, and habitat restoration after construction can help mitigate the impacts (Geothermal energy – Environmental, Economic, Costs, 2023).

Operational Impacts

Geothermal power plants require water to operate. The hot water extracted from underground reservoirs brings dissolved chemicals to the surface. These can include harmful substances like boron, arsenic, mercury, and ammonia (UCSUSA, 2013). After being used to generate electricity, this geothermal fluid is either injected back underground or discharged on the surface. Surface discharge can pollute nearby water bodies through thermal pollution if the water’s temperature is not reduced first (EIA, 2022).

While geothermal plants emit 97% less greenhouse gases than coal plants, they still release some carbon dioxide and sulfur dioxide. The carbon comes from reservoirs that contain magmatic gases. Sulfur dioxide is also naturally occurring in geothermal fluid. Emissions are much lower compared to fossil fuels. However, hydrogen sulfide levels must be monitored as high concentrations can be dangerous (EIA, 2022).

Enhanced geothermal systems that fracture underground rock through hydraulic stimulation can trigger small earthquakes. However, induced seismic activity is less of an issue for conventional hydrothermal reservoirs (UCSUSA, 2013). Overall, geothermal operational impacts are substantially lower than coal or natural gas.

Direct Habitat Impacts

Geothermal power plants require land to be cleared for construction of the power plant and its supporting infrastructure like roads, transmission lines and pipelines. This direct habitat loss can fragment habitats and disrupt wildlife corridors (Source). Fragmented habitats make it difficult for wildlife to find food, water, mates and shelter. Linear infrastructure like roads and pipelines also increases roadkill risks for wildlife.

Construction activity directly removes vegetation from the site, resulting in permanent habitat loss if not restored after. According to the U.S. Fish and Wildlife Service, geothermal development impacts about 5 acres per megawatt of installed capacity, which is higher than other renewables like wind and solar (Source). The service estimates geothermal energy production in the U.S. directly affects around 22,000 acres of land.

Compared to fossil fuels, the land footprint of geothermal plants per unit energy produced is small. However, geothermal plants are normally situated in previously undisturbed natural areas. So the habitat impacts are concentrated in sensitive ecosystems even though the total land footprint is low (Source).

Indirect Habitat Impacts

In addition to direct impacts from construction and operation of geothermal plants, there are various indirect effects that can alter habitats in the surrounding region. One of the major indirect impacts relates to downstream effects on water quality and availability. Geothermal plants require large volumes of water for cooling towers and injecting back into reservoirs. This can reduce downstream flows and affect aquatic ecosystems. According to the Union of Concern Scientists, geothermal plants in arid regions like the western U.S. can consume freshwater at rates exceeding 50 million gallons per day, reducing flows critical for fish and wildlife habitats.

Air pollutants emitted from geothermal plants, such as hydrogen sulfide, can also have indirect effects on habitats and species. As reported by the U.S. Department of Energy, hydrogen sulfide emissions have been linked with vegetative damage when the gas accumulates in soils. Additionally, airborne pollutants may alter habitat suitability and migratory patterns for various bird and insect species sensitive to changes in air quality.

Finally, infrastructure like roads, pipelines, and transmission lines built for geothermal development can indirectly fragment and degrade habitats by altering hydrology, introducing invasive species, and disrupting wildlife corridors. Proper siting, construction methods, and mitigation measures are necessary to minimize indirect habitat impacts from geothermal plants. Overall, while geothermal energy has a smaller footprint than fossil fuels, the technology is not without effects on surrounding ecological systems.

Habitat Restoration

Geothermal energy development can impact habitats through the construction of power plants and drilling of wells. However, efforts are underway to rehabilitate and restore habitats after geothermal development.

At geothermal drilling sites, the soil and vegetation is typically removed during construction. Rehabilitation efforts aim to restore the sites by recontouring disturbed areas, redistributing topsoil, and revegetating the area with native plants (https://www.nrel.gov/docs/fy04osti/36219.pdf). This helps to control erosion, stabilize the soil, and provide habitat for native wildlife.

In California, geothermal developers are required to submit habitat restoration plans before starting construction. These plans detail the restoration and revegetation methods to be used, such as salvaging and replanting native vegetation, using native seed mixes, and controlling invasive species. Monitoring is conducted to track the progress of restoration efforts over time (https://eplanning.blm.gov/public_projects/1503166/20024447/250023648/BLM_Geothermal_Program_PEIS.pdf).

Proper site rehabilitation and habitat restoration minimizes long-term impacts to native ecosystems from geothermal development. With careful revegetation and stewardship, habitats can recover and provide benefits to wildlife once again.

Impact Mitigation

There are several strategies that can help minimize habitat disruption from geothermal energy production:

Careful site selection – Avoiding sensitive habitat areas and siting plants in already disturbed areas can reduce habitat impacts (Environmental Impacts of Geothermal Energy).

Limiting surface disturbance – Using drilling methods that minimize surface disturbance, like directional drilling, helps reduce habitat damage (Kristmannsdottir, 2003).

Restoring disturbed areas – Replanting native vegetation and reintroducing native species to disturbed areas can help restore habitats after construction (Geothermal energy and the environment).

Protecting surface water – Proper wastewater disposal, runoff controls, and avoiding sensitive water resources preserves habitat water quality.

Monitoring impacts – Continued monitoring allows identification of unforeseen impacts so mitigation plans can be adapted.

Comparative Habitat Impacts

When compared to other renewable energy sources like wind and solar, geothermal energy has some distinct advantages and disadvantages in terms of habitat impacts. According to a Stanford study, geothermal plants have a smaller land footprint than equivalent solar or wind farms, requiring just 1/1000th the land area per unit of energy produced (Li, 2013).

However, geothermal development can have localized impacts like habitat loss and fragmentation from plant construction, roads, pipelines etc. One analysis found geothermal overall has moderate habitat impacts, lower than hydroelectric but higher than wind or solar (Erinle, n.d.).

Geothermal fluid discharges can also impact aquatic ecosystems through thermal pollution if not properly managed. Proper siting, mitigation strategies like habitat restoration, and technology improvements can reduce geothermal’s habitat effects (Earth Reminder, 2023).

While no energy source is completely free of habitat impacts, geothermal overall seems to have lower land use requirements than solar or wind. With proper siting and mitigation, geothermal can be a relatively habitat-friendly renewable energy option.

Conclusion

In summary, geothermal energy does have some impacts on surrounding habitats, but these can often be mitigated through careful planning and site selection. The direct habitat impacts from construction are relatively small and localized compared to other energy sources. Operational impacts like noise, light pollution, and geothermal fluid emissions can also affect habitats, but strict regulations and mitigation efforts can reduce these effects. Overall, the comparative habitat impacts of geothermal are lower than fossil fuels and can be comparable to other renewables like solar and wind if sited appropriately. With proper siting and mitigation, geothermal energy can provide low-carbon energy with minimal disruption to natural habitats.

Looking forward, continued research into advanced closed-loop geothermal systems and technologies like binary power plants that reinject geothermal fluids may further reduce habitat impacts. Project developers and regulators should emphasize comprehensive impact assessments, careful siting, and robust habitat restoration plans. When these best practices are followed, geothermal energy can provide clean, renewable power while coexisting with healthy, thriving ecosystems.

In conclusion, geothermal energy facilities can affect surrounding habitats, but thoughtful siting and mitigation can limit disruptions. If properly managed, geothermal offers a clean energy source with fewer habitat impacts than most alternatives.