Emissions geothermal power plants

Figure 12 shows the quantity of CO2 emitted into the atmosphere from two geothermal power plants in Iceland and how it compares with CO2 emission from fossil fuel plants. At Krafla, the quantity of C02 emitted per MW-year (MWy) is 8401, which is only about 10% of that from a typical coal-fired power plant (8760 t/MWy, Armannsson Kristmannsdottir 1992). The... 

Bargagli, R., Cateni, D., Nelli, L., Olmastroni, S. Zagarese, B. 1997. Environmental impact of trace element emissions from geothermal power plants. Archives of Environmental Contamination and Toxicology, 33, 172-181. 

This method could be used for nuclear, concentrating solar or geothermal power plants without carbon dioxide emissions. 

Gas Waste Streams. Treated gas can be a product, like a combustible gas, or an emission to be disposed of. An example of the latter is the noncondensable gas emitted from geothermal power plant gas purification units. This stream is a treated waste gas and is vented to the atmosphere after being diluted with cooling-tower ventilation air. 

Brown, F. C., Harvey, W. W., and Warren, R. B., 1980, Control of Hydrogen Sulfide Emission from Geothermal Power Plants, U.S. Department of Energy Report, Geothermal Energy, Contract EY-76-C-02-2730, Final Report Vol. 2. 

It is also likely that as the cost of solar-hydrogen drops, the costs of fossil and nuclear energy will rise. Robert Stavins of Harvard University estimates that if a 100/ton charge is placed on C02 emissions, that would increase the cost of coal-based electricity by 400% and natural gas-based electricity by 100%, making the cost of solar-, wind, and geothermal-based electricity more than competitive. Table 1.62 lists the effect of a 50/ton carbon emission charge on the unit costs of electricity from a variety of power plants. 

However, there does exist a relationship between emissions and electrolysis. Any pollution associated with electricity consumed by the electrolyzer needs to be taken into account. As stated previously, one fundamental appeal of electrolysis is that it creates a path for converting renewable power into fuel. But the low capacity factors of renewables (other than geothermal and hydro power) make an allrenewables case very difficult on an economic basis. Electricity from nuclear plants is also non-emitting on a greenhouse gas emissions basis, but the outlook for additional nuclear plants is uncertain at best. 

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