Editing Portland cement (section)

==Cement plants used for waste disposal or processing==
[[File:LDWisconsinTireInject.jpg|thumb|Used tyres being fed to a pair of [[cement kiln]]s]]
Due to the high temperatures inside [[cement kiln]]s, combined with the oxidising (oxygen-rich) atmosphere and long residence times, cement kilns are used as a processing option for various types of waste streams; indeed, they efficiently destroy many hazardous organic compounds. The waste streams also often contain combustible materials which allow the substitution of part of the fossil fuel normally used in the process.

Waste materials used in cement kilns as a fuel supplement:<ref>{{cite web|url=http://www.wbcsdcement.org/pdf/lafarge1_en.pdf|title=Recovery of Wastes in Cement Kilns|author=Chris Boyd|publisher=[[World Business Council for Sustainable Development]]|date=December 2001|access-date=2008-09-25|url-status=usurped|archive-url=https://web.archive.org/web/20080624230936/http://www.wbcsdcement.org/pdf/lafarge1_en.pdf<!--Bot retrieved archive-->|archive-date=24 June 2008}}</ref>

*Car and truck [[tire]]s – steel belts are easily tolerated in the kilns
*Paint sludge from automobile industries
*Waste solvents and lubricants
*[[Meat and bone meal]] – [[slaughterhouse]] waste due to [[bovine spongiform encephalopathy]] contamination concerns
*Waste plastics
*Sewage [[sludge]]
*[[Rice hulls]]
*[[Sugarcane]] waste
*Used wooden [[railroad tie]]s (railway sleepers)
*[[Spent potlining|Spent cell liner]] from the aluminium smelting industry (also called [[Spent potlining|spent pot liner]])

Portland cement manufacture also has the potential to benefit from using industrial byproducts from the waste stream.<ref>{{cite book|author1=S.H. Kosmatka|author2=W.C. Panarese|title=Design and Control of Concrete Mixtures|publisher=[[Portland Cement Association]]|year=1988|location=[[Skokie, Illinois]]|page=15|isbn=978-0-89312-087-0|quote=As a generalization, probably 50% of all industrial byproducts have potential as raw materials for the manufacture of portland cement.}}</ref> These include in particular:
*[[Slag]]
*[[Fly ash]] (from power plants)
*[[Silica fume]] (from steel mills)
*Synthetic [[gypsum]] (from [[Desulfurization|desulphurisation]])