Editing Sulfur dioxide (section)

====Control measures====
[[File:Estimates of past and future SO2 global anthropogenic emissions.png|thumb|upright=1.25|Early 2010s estimates of past and future anthropogenic global sulfur dioxide emissions, including the [[Representative Concentration Pathway]]s. While no [[climate change scenario]] may reach Maximum Feasible Reductions (MFRs), all assume steep declines from today's levels. By 2019, sulfate emission reductions were confirmed to proceed at a very fast rate.<ref name=XuRamanathanVictor>{{Cite journal|last1=Xu|first1=Yangyang|last2=Ramanathan|first2=Veerabhadran|last3=Victor|first3=David G.|date=December 5, 2018|title=Global warming will happen faster than we think|journal=Nature|language=en|volume=564|issue=7734|pages=30–32 |url=https://www.researchgate.net/publication/329411074 |doi=10.1038/d41586-018-07586-5|pmid=30518902|bibcode=2018Natur.564...30X|doi-access=free}}</ref>]]
Due largely to the US EPA's [[Acid Rain Program]], the U.S. has had a 33% decrease in emissions between 1983 and 2002 (see table). This improvement resulted in part from [[flue-gas desulfurization]], a technology that enables SO<sub>2</sub> to be chemically bound in [[power plant]]s burning sulfur-containing coal or petroleum.
{| class="wikitable"
|-
! Year
! SO<sub>2</sub>
|-
| 1970
| {{convert|31161000|ST|Mt|sigfig=3}}
|-
| 1980
| {{convert|25905000|ST|Mt|sigfig=3}}
|-
| 1990
|{{convert|23678000|ST|Mt|sigfig=3}}
|-
| 1996
|{{convert|18859000|ST|Mt|sigfig=3}}
|-
| 1997
|{{convert|19363000|ST|Mt|sigfig=3}}
|-
| 1998
|{{convert|19491000|ST|Mt|sigfig=3}}
|-
| 1999
|{{convert|18867000|ST|Mt|sigfig=3}}
|}

In particular, [[calcium oxide|calcium oxide (lime)]] reacts with sulfur dioxide to form [[calcium sulfite]]:

: CaO + SO<sub>2</sub> →  CaSO<sub>3</sub>

Aerobic oxidation of the CaSO<sub>3</sub> gives CaSO<sub>4</sub>, [[anhydrite]]. Most gypsum sold in Europe comes from flue-gas desulfurization.

To control sulfur emissions, dozens of methods with relatively high efficiencies have been developed for fitting of coal-fired power plants.<ref>{{Cite journal|last1=Lin|first1=Cheng-Kuan|last2=Lin|first2=Ro-Ting|last3=Chen|first3=Pi-Cheng|last4=Wang|first4=Pu|last5=De Marcellis-Warin|first5=Nathalie|last6=Zigler|first6=Corwin|last7=Christiani|first7=David C.|date=February 8, 2018|title=A Global Perspective on Sulfur Oxide Controls in Coal-Fired Power Plants and Cardiovascular Disease|journal=Scientific Reports|language=en|volume=8|issue=1|pages=2611 |doi=10.1038/s41598-018-20404-2|pmid=29422539|issn=2045-2322|pmc=5805744|bibcode=2018NatSR...8.2611L}}</ref> Sulfur can be removed from coal during burning by using limestone as a bed material in [[fluidized bed combustion]].<ref>{{cite book |last=Lindeburg |first=Michael R. |title=Mechanical Engineering Reference Manual for the PE Exam |location=Belmont, C.A. |publisher=Professional Publications, Inc |year=2006 |pages=27–3 |isbn=978-1-59126-049-3}}</ref>

Sulfur can also be removed from fuels before burning, preventing formation of SO<sub>2</sub> when the fuel is burnt. The [[Claus process]] is used in refineries to produce sulfur as a byproduct. The [[Stretford process]] has also been used to remove sulfur from fuel. [[Redox]] processes using iron oxides can also be used, for example, Lo-Cat<ref>[https://web.archive.org/web/20100304170107/http://www.gtp-merichem.com/support/index.php FAQ's About Sulfur Removal and Recovery using the LO-CAT® Hydrogen Sulfide Removal System]. gtp-merichem.com</ref> or Sulferox.<ref>[http://www.netl.doe.gov/technologies/coalpower/gasification/pubs/pdf/SFA%20Pacific_Process%20Screening%20Analysis_Dec%202002.pdf Process screening analysis of alternative gas treating and sulfur removal for gasification]. (December 2002) Report by SFA Pacific, Inc. prepared for U.S. Department of Energy (PDF) Retrieved on October 31, 2011.</ref>

Fuel additives such as [[calcium]] additives and magnesium carboxylate may be used in marine engines to lower the emission of sulfur dioxide gases into the atmosphere.<ref>May, Walter R.  [http://www.fuelspec.com/library/Marine%20Emissions%20Abatement.pdf Marine Emissions Abatement] {{Webarchive|url=https://web.archive.org/web/20150402130001/http://www.fuelspec.com/library/Marine%20Emissions%20Abatement.pdf |date=April 2, 2015 }}. SFA International, Inc., p. 6.</ref>