Editing Portland cement (section)

==Environmental effects==
{{More citations needed section|date=February 2020}}
Portland cement manufacture can cause [[Environmental impact of concrete|environmental impacts]] at all stages of the process. These include [[Cement kiln emissions|emissions]] of airborne pollution in the form of dust; gases; noise and vibration when operating machinery and during blasting in quarries; consumption of large quantities of fuel during manufacture; release of {{chem|C|O|2}} from the raw materials during manufacture, and damage to countryside from quarrying. Equipment to reduce dust emissions during quarrying and manufacture of cement is widely used, and equipment to trap and separate exhaust gases are coming into increased use. Environmental protection also includes the re-integration of quarries into the countryside after they have been closed down by returning them to nature or re-cultivating them.

Portland cement is [[Corrosive substance|caustic]], so it can cause chemical burns.<ref name=ASTM>{{cite journal|url=http://www.ASTM.org/cgi-bin/resolver.cgi?C185|title=ASTM C185-15a, Standard Test Method for Air Content of Hydraulic Cement Mortar|publisher=[[ASTM International]]|location=West Conshohocken, PA|year=2015|website=www.ASTM.org|doi=10.1520/C0185-15A|access-date=16 May 2017}}</ref> The powder can cause irritation or, with severe exposure, lung cancer, and can contain a number of hazardous components, including crystalline [[silica]] and [[hexavalent chromium]]. Environmental concerns are the high energy consumption required to mine, manufacture, and transport the cement, and the related air pollution, including the release of the [[greenhouse gas]] [[carbon dioxide]], [[Dioxins and dioxin-like compounds|dioxin]],{{Citation needed|date=June 2021}} {{chem2|NO_{x} }}, {{chem2|SO2}}, and [[particulates]]. Production of portland cement contributes about 10% of world [[carbon dioxide emissions]].<ref>{{cite journal|last1=Scrivener|first1=Karen L.|last2=John|first2=Vanderley M.|last3=Gartner|first3=Ellis M.|title=Eco-efficient cements: Potential economically viable solutions for a low-CO<sub>2</sub> cement-based materials industry|journal=Cement and Concrete Research|volume=114|pages=2–26|date=June 2018|doi=10.1016/j.cemconres.2018.03.015|url=http://spiral.imperial.ac.uk/bitstream/10044/1/51016/2/2016-UNEP%20Report-Complete6.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://spiral.imperial.ac.uk/bitstream/10044/1/51016/2/2016-UNEP%20Report-Complete6.pdf |archive-date=2022-10-09 |url-status=live|hdl=10044/1/51016|s2cid=139685537|hdl-access=free}}</ref> The [[International Energy Agency]] has estimated that cement production will increase by between 12 and 23% by 2050 to meet the needs of the world's growing population.<ref>{{cite web|title=Technology Roadmap - Low-Carbon Transition in the Cement Industry: Foldout|url=https://webstore.iea.org/technology-roadmap-low-carbon-transition-in-the-cement-industry-foldout|website=IEA webstore}}</ref> There are several ongoing researches targeting a suitable replacement of portland cement by [[supplementary cementitious materials]].<ref>{{cite journal|last1=Lothenbach|first1=Barbara|last2=Scrivener|first2=Karen|last3=Hooton|first3=R.D.|title=Supplementary cementitious materials|journal=Cement and Concrete Research|date=December 2011|volume=41|issue=12|pages=1244–1256|doi=10.1016/j.cemconres.2010.12.001}}</ref>

''Epidemiologic Notes and Reports Sulfur Dioxide Exposure in Portland Cement Plants'', from the [[Centers for Disease Control]], states:

{{blockquote|Workers at portland cement facilities, particularly those burning fuel containing sulfur, should be aware of the acute and chronic effects of exposure to {{chem|S|O|2}} [sulfur dioxide], and peak and full-shift concentrations of {{chem|S|O|2}} should be periodically measured.<ref>{{cite web|url=https://www.cdc.gov/mmwr/preview/mmwrhtml/00000317.htm|title=Epidemiologic Notes and Reports Sulfur Dioxide Exposure in Portland Cement Plants|work=cdc.gov|url-status=live|archive-url=https://web.archive.org/web/20170625233757/https://www.cdc.gov/mmwr/preview/mmwrhtml/00000317.htm|archive-date=25 June 2017|df=dmy-all}}</ref>}}

An independent research effort of [[AEA Technology]] to identify critical issues for the cement industry today concluded the most important [[environment, health and safety]] performance issues facing the cement industry are atmospheric releases (including [[greenhouse gas emissions]], dioxin, {{chem2|NO_{x} }}, {{chem|S|O|2}}, and particulates), accidents, and worker exposure to dust.<ref>{{cite web|url=http://www.wbcsd.ch/web/projects/cement/tf3/final_report10.pdf|title=Toward a Sustainable Cement Industry: Environment, Health & Safety Performance Improvement|work=wbcsd.ch|url-status=dead|archive-url=https://web.archive.org/web/20070928064634/http://www.wbcsd.ch/web/projects/cement/tf3/final_report10.pdf|archive-date=28 September 2007|df=dmy-all|access-date=5 December 2006}}</ref>{{Better source needed|date=June 2021}}

The {{chem|C|O|2}} associated with portland cement manufacture comes mainly from four sources:
{|class="wikitable"
|-
! {{chem|C|O|2}} source
! Amount
|-
| Decarbonation of [[limestone]]
| Fairly constant: minimum around {{nobreak|{{cvt|0.47|kg}}}} {{chem|C|O|2}} per kg of cement, maximum 0.54, typical value around 0.50 worldwide.{{Citation needed|date=August 2010}}
|-
| Kiln fuel combustion
| Varies with plant efficiency: efficient precalciner plant {{nobreak|{{cvt|0.24|kg}}}} {{chem|C|O|2}} per kg cement, low-efficiency wet process as high as 0.65, typical modern practices (e.g. UK) averaging around 0.30.{{Citation needed|date=August 2010}}
|-
| Produced by vehicles in cement plants and distribution
| Almost insignificant at 0.002–0.005. So typical total {{chem|C|O|2}} is around {{nobreak|{{cvt|0.80|kg}}}} {{chem|C|O|2}} per kg finished cement.
|-
| Electrical power generation
| Varies with local power source. Typical electrical energy consumption is on the order of 90–150 kWh per tonne cement, equivalent to {{nobreak|{{cvt|0.09–0.15|kg}}}} {{chem|C|O|2}} per kg finished cement if the electricity is coal-generated.
|}

Overall, with nuclear or hydroelectric power, and efficient manufacturing, {{chem|C|O|2}} generation can be reduced to {{nobreak|{{cvt|0.7|kg}}}} per kg cement, but can be twice as high.{{clarify|date=February 2020}} The thrust of innovation for the future is to reduce sources 1 and 2 by modification of the chemistry of cement, by the use of wastes, and by adopting more efficient processes.{{citation needed|date=February 2020}} Although cement manufacturing is clearly a very large {{chem|C|O|2}} emitter, concrete (of which cement makes up about 15%) compares quite favourably with other modern building systems in this regard.{{Citation needed|date=July 2008}}. Traditional materials such as lime based mortars as well as timber and earth based construction methods emit significantly less {{CO2}}.<ref>{{Cite web |last=Kent |first=Douglas |date=2007-10-22 |title=Response: Lime is a much greener option than cement, says Douglas Kent |url=http://www.theguardian.com/commentisfree/2007/oct/23/comment.comment |access-date=2022-03-22 |website=the Guardian |language=en}}</ref>