Enhanced geothermal systems have been touted as an important renewable energy technology for meeting global climate goals, but some concern exists over just how environmentally friendly this technology really is. In anticipation of potential backlash from the anti-fracking community, EGS advocates are working to ensure that this technology can be a viable source of geothermal energy.
A geothermal system allows human technology to harness heat within the earth’s crust to generate electricity. While this alternative energy system is distinct from the traditional use of fossil fuels, is it really a sustainable method for the long term?
How Geothermal Energy Works
There are two types of geothermal systems: hydrothermal systems and enhanced geothermal systems (or EGS). The former occurs naturally in the earth’s crust, and its definition as a hydrothermal system depends on heat, fluid and permeability at depth. In layman’s terms, a naturally occurring geothermal system consists of a hot spring associated with volcanic activity.
On the other hand, an EGS is a manmade reservoir. Technicians find areas of hot rock that lack the necessary fluid or permeability and inject fluid into the subsurface to cause the fractures to reopen.
With this increased permeability, fluid can circulate freely throughout the newly fractured hot rock, transporting the energy to the surface to generate electricity. Proponents of this technology advocate EGS as a clean way to harness an enormous energy resource within the United States.
Comparison to Hydraulic Fracturing
Hydraulic fracturing, or fracking, has come under major fire among environmentalist advocates in the United States – and EGS has been described as “geothermal fracking.” The process is similar, after all. It involves drilling into the earth, injecting water and chemical mixtures at high pressures into the ground, and breaking open cracks in the rock below the surface.
However, the geothermal industry has insisted that there is a massive difference. For instance, new geothermal technology doesn’t involve burning hydrocarbons, while conventional fracking does. Proponents of the technology assert that EGS is a low-carbon or carbon-neutral process with few problematic emissions.
Advocates of EGS distinguish between traditional fracking technology and EGS, which they refer to as “slipping” rather than fracking. Instead of using a chemical mixture, EGS involves high-pressure water and sometimes acid (“very dilute,” they say). Lauren Boyd, the EGS program manager at the U.S. Department of Energy (DOE), compares the process to dropping an ice cube into a glass of hot liquid. The ice will crack along existing deformities, which is “similar to what happens in the subsurface with closed fractures” in hot rock.
The Overall Impact of Geothermal on the Environment
According to The Economist, there is no tangible difference between EGS and conventional fracking in terms of environmental impact. EGS can trigger earthquakes, most of which are very small and virtually unnoticeable. However, one early EGS in Basel, Switzerland created a major series of earthquakes because the process was initiated on a seismic fault. This project was quickly abandoned after researchers concluded that continuing would create massive amounts of damage in the years to come.
Critics continue to bring up the Basel project as an example of why geothermal fracturing should be avoided. The DOE has forged ahead regardless, with a new project in Bend, Oregon. As with the Bend project, the DOE has ensured that every domestic project is carefully monitored by seismometers in an attempt to assuage the concerns of environmental advocates. Nevertheless, critics continue to assert that acidic mixtures used for EGS may leak, contaminating surrounding soil and groundwater. As a result, local ecosystems may be severely compromised.
As of yet, EGS has not come under fire from anti-fracking activists on a major scale. Nevertheless, the DOE and other advocates of EGS have braced themselves by implementing every possible preventative measure against environmental contamination, seismic activity, and carbon emissions. It seems that EGS will still see significant public debate, but only time will tell if it becomes a viable source of geothermal energy regardless.