Editing Biogas (section)

=== Contaminants ===
==== Sulfur compounds ====
Toxic, corrosive and foul smelling [[hydrogen sulfide]] ({{chem|H|2|S}}) is the most common contaminant in biogas. If not separated, combustion will produce [[sulfur dioxide]] ({{chem|SO|2}}) and [[sulfuric acid]] ({{chem|H|2|SO|4}}), which are corrosive and environmentally hazardous.,<ref name="AbatzoglouBoivin2009" /> Other sulfur-containing compounds, such as [[thiols]] may be present.

==== Ammonia ====
[[Ammonia]] ({{chem|NH|3}}) is produced from organic compounds containing nitrogen, such as the [[amino acids]] in [[proteins]]. If not separated from the biogas, combustion results in [[NOx|{{chem|NO|x}}]] emissions.<ref name="AbatzoglouBoivin2009"/>

==== Siloxanes ====
In some cases, biogas contains [[siloxanes]]. They are formed from the [[anaerobic decomposition]] of materials commonly found in soaps and detergents. During combustion of biogas containing siloxanes, [[silicon]] is released and can combine with free oxygen or other elements in the [[combustion gas]]. Deposits are formed containing mostly [[silica]] ({{chem|SiO|2}}) or [[silicates]] ({{chem|Si|''x''|O|''y''}}) and can contain [[calcium]], [[sulfur]], [[zinc]], [[phosphorus]]. Such ''white mineral'' deposits accumulate to a surface thickness of several millimeters and must be removed by chemical or mechanical means.

Practical and cost-effective technologies to remove siloxanes and other biogas contaminants are available.<ref name="BiogasSiloxaneRemoval">{{cite web|url=http://biogas-digester.com/biogas-technology-lowers-costs.html|title=New Landfill Gas Treatment Technology Dramatically Lowers Energy Production Costs|last=Tower|first=P.|author2=Wetzel, J.|author3=Lombard, X.|date=March 2006|publisher=Applied Filter Technology|access-date=30 April 2009|archive-url=https://web.archive.org/web/20160102055113/http://biogas-digester.com/biogas-technology-lowers-costs.html|archive-date=2 January 2016|url-status=dead}}(broken link)</ref>