Editing Geothermal energy (section)

==Environmental effects==
[[File:Puhagan geothermal plant.jpg|thumb|Geothermal power station in the Philippines]]
[[File:Krafla Geothermal Station.jpg|thumb|Krafla Geothermal Station in northeast Iceland]]

Fluids drawn from underground carry a mixture of gasses, notably [[carbon dioxide]] ({{chem|CO|2|}}), [[hydrogen sulfide]] ({{chem|H|2|S|}}), [[methane]] ({{chem|CH|4|}}) and [[ammonia]] ({{chem|NH|3|}}). These pollutants contribute to [[global warming]], [[acid rain]] and noxious smells if released. Existing geothermal electric plants emit an average of {{convert|122|kg|lb}} of {{chem|CO|2|}} per megawatt-hour (MW·h) of electricity, a small fraction of the [[emission intensity]] of fossil fuel plants.<ref name="CO2">
{{Citation
| last1 = Bertani | first1 = Ruggero
| last2 = Thain | first2 = Ian
| title = Geothermal Power Generating Plant CO<sub>2</sub> Emission Survey
| journal = IGA News
| issue = 49
| pages = 1–3
| date = July 2002
| url = http://www.geothermal-energy.org/files-39.html
| archive-url = https://web.archive.org/web/20110726100945/http://www.geothermal-energy.org/files-39.html
| archive-date = 2011-07-26
| access-date = 2010-01-17
}}</ref>{{Update inline|date=October 2020|reason=Lots of new geothermal since 2002}} A few plants emit more pollutants than gas-fired power, at least in the first few years, such as some [[geothermal power in Turkey]].<ref>{{Citation|last1=Tut Haklidir|first1=Fusun S.|title=Global CO2 Capture and Storage Methods and a New Approach to Reduce the Emissions of Geothermal Power Plants with High CO2 Emissions: A Case Study from Turkey|date=2019|work=Climate Change and Energy Dynamics in the Middle East: Modeling and Simulation-Based Solutions|pages=323–357|editor-last=Qudrat-Ullah|editor-first=Hassan|series=Understanding Complex Systems|publisher=Springer International Publishing|doi=10.1007/978-3-030-11202-8_12|isbn=9783030112028|last2=Baytar|first2=Kaan|last3=Kekevi|first3=Mert|s2cid=133813028 |editor2-last=Kayal|editor2-first=Aymen A.|quote=CO2 emissions emitted by the geothermal power plants range from 900 to 1300 gr/kwh}}</ref> Plants that experience high levels of acids and volatile chemicals are typically equipped with emission-control systems to reduce the exhaust. New emerging closed looped technologies developed by Eavor have the potential to reduce these emissions to zero.<ref name=":5">{{Cite web |date=2019-04-24 |title=Eavor-Loop Demonstration Project |url=https://natural-resources.canada.ca/science-and-data/funding-partnerships/funding-opportunities/current-investments/eavor-loop-demonstration-project/21896 |access-date=2024-02-10 |website=Natural Resources Canada}}</ref>

Water from geothermal sources may hold in solution trace amounts of toxic elements such as [[Mercury (element)|mercury]], [[arsenic]], [[boron]], and [[antimony]].<ref name="toxic">{{Citation | last1 = Bargagli | first1 = R. | last2 = Catenil | first2 = D. | last3 = Nellil | first3 = L. | last4 = Olmastronil | first4 = S. | last5 = Zagarese | first5 = B. | s2cid = 30238608 | title = Environmental Impact of Trace Element Emissions from Geothermal Power Plants | journal = Environmental Contamination Toxicology | volume = 33 | issue = 2 | pages = 172–181 | year =1997 | doi = 10.1007/s002449900239| pmid = 9294245 }}</ref>  These chemicals precipitate as the water cools, and can damage surroundings if released. The modern practice of returning geothermal fluids into the Earth to stimulate production has the side benefit of reducing this environmental impact.

Construction can adversely affect land stability. [[Subsidence]] occurred in the Wairakei field.<ref name="utilization" /> In [[Staufen im Breisgau]], Germany, [[tectonic uplift]] occurred instead. A previously isolated [[anhydrite]] layer came in contact with water and turned it into gypsum, doubling its volume.<ref>{{cite web|url=http://www1.eere.energy.gov/geothermal/low_temperature_resources.html |title=Staufen: Risse: Hoffnung in Staufen: Quellvorgänge lassen nach |publisher=badische-zeitung.de |access-date=2013-04-24}}</ref><ref>{{Cite web |title=Relaunch explanation |url=https://www.dlr.de/EN/Service/about-relaunch/explanation.html |access-date=2022-08-05 |website=NAV_NODE DLR Portal |language=en |archive-date=2020-05-08 |archive-url=https://web.archive.org/web/20200508000704/https://www.dlr.de/EN/Service/about-relaunch/explanation.html |url-status=dead }}</ref><ref>{{Cite web |title=WECHSELWIRKUNG - Numerische Geotechnik |url=http://www.wechselwirkung.eu/en/reference_stau.php |access-date=2022-08-05 |website=www.wechselwirkung.eu}}</ref> [[Enhanced geothermal systems]] can trigger [[earthquake]]s as part of [[hydraulic fracturing]]. A project in [[Basel]], [[Switzerland]] was suspended because more than 10,000 seismic events measuring up to 3.4 on the [[Richter Scale]] occurred over the first 6 days of water injection.<ref>
{{Citation| first1 = N.| last1 = Deichmann| title = Seismicity Induced by Water Injection for Geothermal Reservoir Stimulation 5&nbsp;km Below the City of Basel, Switzerland| year = 2007| bibcode = 2007AGUFM.V53F..08D| last2 = Mai| last3 = Bethmann
| last4 = Ernst| last5 = Evans| last6 = Fäh| last7 = Giardini| last8 = Häring| last9 = Husen| volume = 53| pages = V53F–08 | journal = American Geophysical Union|display-authors=etal}}</ref>

Geothermal power production has minimal land and freshwater requirements. Geothermal plants use {{convert|3.5|km2}} per&nbsp;gigawatt of electrical production (not capacity) versus {{convert|32|km2}} and {{convert|12|km2}} for [[coal]] facilities and [[wind farm]]s respectively.<ref name="utilization" /> They use {{convert|20|L|usgal}} of freshwater per MW·h versus over {{convert|1000|L|usgal}} per&nbsp;MW·h for nuclear, coal, or oil.<ref name="utilization" />