Heat generated by underground volcanic activity can and has been harnessed for electricity for over 100 years around the world.

Dear EarthTalk: Is there any way to harness volcanic energy to meet our electricity and other power needs?

— Antonio Lopez, Chino, Calif.

The short answer is yes: Heat generated by underground volcanic activity can and has been harnessed for electricity for over 100 years around the world. Utilities can capture the steam from underground water heated by magma and use it to drive the turbines in geothermal power plants to produce significant amounts of electricity. Getting at the sources is not so easy or cheap, though, as it requires drilling into unstable sections of the Earth's crust and then harnessing the heat energy miles below the surface.

Despite these difficulties, volcanic geothermal energy reserves account for about a quarter of Iceland's energy consumption (with the rest taken up by another clean renewable resource, hydropower dams). According to statistics from the Geothermal Energy Association, the Philippines is also a big user of geothermal power: About 18 percent of that country's electricity comes from underground volcanic sources. And in New Zealand, geothermal accounts for about 10 percent of total electricity consumption.

But believe it or not, the United States is actually the world's largest producer of volcano-derived geothermal electricity, but still only derives less than one percent of its total power from such sources. California and Nevada are the leaders in this nascent form of renewable energy domestically, but promising efforts are also underway in Oregon, Utah, Alaska and Hawaii. Some analysts believe that the U.S. has enough geothermal capacity to provide 20 percent or more of the nation's electricity needs.

Against the backdrop of diminishing oil reserves, tapping volcanic energy has become a high priority for some other regions as well. The war-ravaged East African nation of Rwanda is hoping to provide power for its people by harnessing the energy from volcanic gases at Lake Kivu, one of the continent's largest lakes, covering some 1,000 square miles. The lake is one of three known "exploding" lakes subject to violent and sometimes deadly "overturns" triggered by volcanic activity. Methane and carbon dioxide from an adjacent volcano mix methane and carbon dioxide into the lake, making it a veritable tinder box, threatening the lives and homes of some two million people in the region.

In response to the risk—and also to produce energy—the Rwandan government has started using a large barge to suck up water and extract the methane gas therein. The methane is then used to fire the gas-powered Kibuye power plant. Already the system is producing 3.6 megawatts of electricity—some four percent of Rwanda's total power supply. Within a few years, project backers hope to be generating between 50 and 100 megawatts of power from the operation. Extracting the methane also significantly reduces the risk of explosions, thus providing a measure of safety for area residents.

Humans have barely put a dent in the amount of power that can be captured from volcanic activity, but analysts expect to see much more of this form of power coming online over the next few decades. The U.S. Geological Survey refers to this phenomenon as the "plus side of volcanoes." Environmentalists and others are hopeful that volcanic geothermal energy can become a major player in meeting a significant portion of our energy needs in our increasingly carbon-constrained world.

CONTACTS: Geothermal Energy Association, www.geo-energy.org U.S. Geological Survey, www.usgs.gov.

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