When it comes to geothermal energy, nowhere on the planet is more naturally equipped than Iceland. The country boasts gushing geysers and endless fields of hot springs, all of which can provide safe conventional geothermal energy; by capturing the earth’s hot water and creating steam, this little-known energy source could supply power to millions of homes.
Outside of Iceland, however, implementing geothermal energy reserves gets more complicated.
Earthquake expert Dr. Emily Brodsky explains Enhanced Geothermal Systems (EGS), more commonly known as “hot dry rock,” hold an abundance of hot water in the earth’s subsurface – but its steam doesn’t rise to the surface by itself.
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Therefore, increasing the permeability of these subsurface rocks is essential to the EGS operation. To do so, scientists use pressurized chemicals to fracture the rocks and create a cycle whereby water is injected into the earth to be heated and is then brought back to the surface to use as an energy source. Unfortunately, chemical use during the EGS process can result in negative consequences.
Hydraulic fracturing chemicals used in non-geothermal systems are much different from those used in geothermal systems, Brodsky says. One of the main concerns in geothermal fracking is that the chemicals used will break down under the heat and “drop [their] load of mineral precipitates,” clogging pipes.
The other big concern? Earthquakes.
Brodsky, a geophysicist of 20 years, says breaking up rocks to clear a path for hot water holds both costs and benefits. In deeper, tighter formations – such as the ones used to create geothermal energy – pulling fluids in and out of the ground can stress surrounding rocks.
“It’s intrinsic in the EGS process that earthquakes happen,” says Brodsky, a professor of earth and planetary sciences at the University of California, Santa Cruz. “Two different things are creating the earthquakes. One is creating permeability in the first place, and once in operational mode, that the earthquakes continue.”
Generally speaking, she says EGS takes place deep below the ground and far from the water table, so there is minimal concern about contaminating groundwater. Another advantage of fracking geothermal energy is that it is still less harmful to the environment than fracking for fossil fuels.
The downside, however, is that geothermal systems tend to be situated along already-strained fault lines – one example being the San Andreas fault line, which has major geothermal plants on both ends of the fault line.
“The cost of it is… earthquakes. It needs to be used with a certain amount of discretion,” Brodsky warns. “There are places in the world where geothermal is a great technology, and there are places where you might think this is not such a clever idea.”
Although there are certainly limitations to today’s geothermal mechanics, the clean energy source may one day beat out hydraulic fracking for oil or gas. Until its technology improves, oil and gas will remain the popular fracking choices.
To extract oil through fracking, chemicals are injected into the ground to break up rocks and release trapped oil, which then flows to the surface. This process, however, has more risks than that of geothermal fracking; hydraulic fracturing, if not done properly, can release radioactive wastewater and severely damage fault lines.
John Fleming, a staff scientist with the Center for Biological Diversity’s Climate Law Institute, says a majority of California’s hydraulic fracturing occurs in shallow wells – about 600 meters or less – which is roughly level with the groundwater. If the fractures intersect with groundwater supply, the practice increases the risk of contaminating communities, he says.
Hydraulic Fracturing – What’s in the water?
Through the oil fracking process, the wastewater produced is “disposed of” by re-injecting it into the ground. A few years ago, a fracking field contaminated a nearby supply of drinking water, which raised health and safety concerns in California.
“There was a lot of this injection of wastewater back underground illegally into water that is considered to be underground sources of drinking water. [That led to] the Safe Drinking Water Act. Since then, there’s been an effort to retroactively legalize the injection in that case,” Fleming says.
In Oklahoma, fracking caused a number of severe earthquakes, prompting the recently settled lawsuit. The tremors there have since subsided, but Fleming says California faces similar fears of induced earthquakes attributed to wastewater disposal at fracking sites.
California’s Kern County has borne the brunt of these quakes, since it is where most of the state’s oil and gas extractions occur.
“The issue is that if you’re changing underground pressures. Those pressures can impact a nearby fault and cause those faults to slip where they otherwise might not slip,” Fleming explains.
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He worries that the fracking process and over-extraction of lighter oil will trigger more faults.
As oil fields age, their oil becomes harder to extract; many of California’s oil fields have been extracted for so long that all that remains is heavy, viscous oil. Like tar, it doesn’t flow easily, and releases more carbon dioxide emissions than lighter oil.
“You’re able to refine it, but that process takes more input and energy [in] burning the product than when you’re burning lighter oil,” Fleming says.
These days, he feels the problem has passed the point of finding middle ground on the issue of fracking. And as the debate rages on, oil fields continue to pump more chemicals into the ground.
In an effort to spread awareness of the harmful effects of fracking, Fleming’s organization leads a campaign in the city of Los Angeles to phase out oil drilling in places where people live within a matter of feet from oil or gas wells. All of these areas are reporting serious health issues, from contaminated water to toxic air.
“It comes down to fracking, and pathways for fluids to flow, and some of those harmful fluids, harmful chemicals getting into groundwater along with the air.”
Dianne Anderson covers education, health, and city government stories with an eye on legislative impacts to diverse communities. She has received awards from the American Cancer Society – Inland Empire, and the Southern Poverty Law Center. Over the years, she has reported for the Long Beach Leader and the Inland Valley Daily Bulletin and been a contributor to the Pasadena Weekly.