Interest in geothermal energy development has been increasing in recent years, especially in the West where the majority of the nation’s geothermal resources are found. The West’s geothermal potential was the focus of Colorado Governor Jared Polis’s “Heat Beneath Our Feet” initiative during his recently-concluded chairmanship of the Western Governors’ Association. Geothermal lease sales on national public lands in Western states have also attracted increasing interest: the most recent geothermal lease sale in Nevada in August 2022, for example, set a record for the number of acres leased at nearly 193,000 acres.
While geothermal is getting more attention these days, it is not new. Geothermal energy development takes advantage of the naturally-occurring heat from the Earth’s core and mantle, which heats water deep below the Earth’s surface. In some places, this heated water rises to the surface in the form of hot springs and geysers. Indigenous peoples have been using these naturally-occurring “surface expressions” of geothermal energy for thousands of years. In 1892, the city of Boise, Idaho developed a system to pipe water from a nearby hot spring into buildings to heat them, a system that is still used today to heat buildings downtown. Several other projects followed over the next century, many of which are still operational.
In 1970, President Richard Nixon signed into law the Geothermal Steam Act, which authorized the Secretary of the Interior to lease federally-managed lands for geothermal energy exploration and development, similar to how public lands can be leased for oil and gas development. Current law requires that a geothermal lease sale be held at least every two years in any state that has pending nominations (lands that developers have expressed interest in exploring and developing) for geothermal leasing. A bill proposed by Representative Russ Fulcher of Idaho would increase that to once every year.
Geothermal energy is a potentially appealing energy source because emissions over the entire life cycle of geothermal energy development are typically much lower than emissions from coal, oil, and natural gas. Construction and drilling of wells requires energy and generates emissions, and geothermal sites that extract naturally-occurring hot water can result in emissions of gasses naturally found in the underground water, such as hydrogen sulfide. However, geothermal power plants do not emit greenhouse gasses as a byproduct of energy generation once operational. Overall, life-cycle emissions of geothermal energy are comparable to those of other renewable energy sources such as wind and solar. Geothermal is also categorized as a renewable energy source because its fuel is the heat that is naturally being generated within the Earth’s core and will last for another several billion years.
One of the challenges of geothermal energy development is that it can be hard to find. Unless there is a hot spring or other natural geothermal feature at the surface, it’s not usually obvious where subsurface geothermal resources are. Due in part to these barriers, geothermal contributes less than half a percent of the total energy consumed in the U.S., and only two percent of total renewable energy consumed. Of this, 67 percent is generated on public lands managed by the Bureau of Land Management, and another two percent is generated on public lands managed by the U.S. Forest Service.
However, recent technological advances from the oil and gas industry are helping the geothermal industry explore for, discover and develop geothermal resources. Horizontal drilling makes it easier to identify and exploit a geothermal resource with more flexibility in regard to the placement of surface drilling equipment. Hydraulic fracturing can also be used to engineer geothermal resources by forcing water into hot rocks below the surface and then pumping the heated water back to the surface. And in some cases, existing oil and gas wells can be repurposed as geothermal wells when they are done producing oil and gas.
While geothermal energy shows a lot of promise as low-emissions energy source, it must be developed thoughtfully to avoid negative environmental impacts. Wells and other infrastructure must be carefully evaluated and placed to avoid harm to plants and animals (an issue that can be partially mitigated by using existing oil and gas wells when possible). Some projects have the potential to drain water from springs and wetlands, destroying habitat for unique animals and plants that depend on them. This happens in situations where the geothermal well draws up existing heated water, rather than pumping water into the ground and then bringing that water back up. This can suck water away from the surrounding areas on the surface, leading to what is called “dewatering” of springs and wetlands. For example, in Nevada, the Jersey Valley Hot Springs began to decline shortly after the nearby McGinness Hills geothermal power plant began commercial production. Also in Nevada, the proposed Dixie Meadows geothermal project is undergoing a new environmental review in response to concerns that the project would jeopardize the Dixie Valley toad, which was listed as endangered in December 2022 and which relies on a spring-fed desert wetland in the area of the proposed project.
Similarly, projects that pump water down into the ground and then bring it back up raise concerns about where to obtain that much water, the effects of introducing that much water into the ground, and the amount of water that is lost to the ground during the process. Technologies being explored to solve these problems include developing closed-loop systems, where fluid remains in pipes as it passes through heated rocks below the surface, and using fluids other than water that may absorb and retain heat more efficiently and do not divert water from other uses.
As the United States continues to transition away from fossil fuels, a variety of creative solutions will be needed to meet and reduce our energy demand and to reduce greenhouse gas emissions from energy production. However, no solution is worth bypassing our nation’s environmental safeguards. With thoughtful planning, America can take advantage of renewable energy resources while ensuring the survival of wildlife and their habitats now and in the future.
Feature image: Hot springs in Idaho, Idaho National Laboratory