Somewhat surprisingly, the hot air that carries the heat from the earth
at geothermal sites also contains carbon dioxide, CO2, the Greenhouse Gas
that sends anti-technologists into a frenzy. The suite of 20 geothermal
sites from which Southern California Electric is obligated to buy electricity
produces 730 tonnes of CO2 for every gigawatt-hour (GWh) of electricity
produced.
Across the spectrum of all natural-gas power plants in the US, the average
CO2 production is 519 tonnes per GWh. That is, the geothermal power
plants, which burn no fossil fuels whatsoever, produce 41% more CO2 than
the run-of-the-mill natural gas power plant for the same amount of electrical
energy produced.