Report: Geothermal Offers Reliable Low-Carbon Power

The new John L. Featherstone geothermal plant in Imperial County | Photo: GEA

As California ramps up its new carbon cap and trade program, all eyes are on the operators of large fossil-fueled electrical power stations, and industry that's one of the largest contributors to the state's carbon emissions. Excellent timing, then, for the release of a new report showing that geothermal power plants offer power as reliable and consistent as coal-fired plants, but with only about one-twentieth of the carbon footprint.

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The report, Geothermal Energy and Greenhouse Gas Emissions, was released this week by the trade group the Geothermal Energy Association. With sponsorship like that, it's no surprise that the report's authors sing geothermal's praises.

Still, the figures the report offers are compelling: on average, geothermal plants emit 5% of the carbon dioxide, 1% of the sulfur dioxide, and 1% of the nitrogen oxides emitted by coal plants of the same generating capacity. What's more, according to the report, much of the carbon dioxide emitted by geothermal plants may well have been released anyway: it comes from dissolved carbon dioxide in the thermal water, which might otherwise bubble up to the surface in hot springs or geysers and release the dissolved gases into the atmosphere without human help.

Those carbon dioxide emissions can be avoided altogether by the use of so-called "binary" power plant design, in which hot water or steam from deep in the earth is circulated in a closed system of pipes and then re-injected into the deep geothermal aquifer, keeping any dissolved gases from being discharged into the atmosphere.

Geothermal energy does have a financial downside: unlike many other forms of renewable energy, which can be brought online in small increments such as rooftop solar, geothermal power plants require an industrial-scale development -- and an industrial scale investment to build it. Costs per kilowatt-hour range toward the high end for renewables, and significantly higher than power from plants fueled by currently inexpensive natural gas.

But the state's adding a price for each ton of carbon dioxide emitted by those natural gas plants may well erase some of that advantage. That's an opportunity the geothermal industry is poised to take advantage of, as California works to reduce its greenhouse gas emissions 25% by 2020. "This ambitious goal will serve to mitigate global climate change and increase America's energy security, and geothermal is poised to provide the Golden State with the roadmap to meet this target," said GEA Executive Director Karl Gawell. "California's program should serve as a model for other states and the federal government as we seek energy independence, job growth and a cleaner, safer environment for future generations."

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About the Author

Chris Clarke is a natural history writer and environmental journalist currently at work on a book about the Joshua tree. He lives in Joshua Tree.
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