Editing Biogas (section)

===Biogas in transport===
[[File:Biogas-train-amanda-in-linkoping-2006.JPG|thumb|250px|"Biogaståget Amanda" ("Amanda the Biogas Train") train near [[Linköping]] station, Sweden]]
If concentrated and compressed, it can be used in vehicle transportation. Compressed biogas is becoming widely used in Sweden, Switzerland, and Germany. A biogas-powered train, named Biogaståget Amanda (The Biogas Train Amanda), has been in service in Sweden since 2005.<ref>[http://www.svenskbiogas.se/sb/docs/english/Biogastrain_produktblad_2005.pdf Biogas train in Sweden] {{webarchive|url=https://web.archive.org/web/20110929143008/http://www.svenskbiogas.se/sb/docs/english/Biogastrain_produktblad_2005.pdf |date=29 September 2011}}</ref><ref>Friendly fuel trains (30 October 2005) [[New Straits Times]], p. F17.</ref> Biogas powers automobiles. In 1974, a British documentary film titled ''Sweet as a Nut'' detailed the biogas production process from pig manure and showed how it fueled a custom-adapted combustion engine.<ref>{{cite web|url=http://ftvdb.bfi.org.uk/sift/title/96790|title=Bates Car – Sweet As a Nut (1975)|work=BFI|access-date=15 May 2015|archive-url=https://web.archive.org/web/20130723061106/http://ftvdb.bfi.org.uk/sift/title/96790|archive-date=23 July 2013|url-status=dead}}</ref><ref>{{cite web|url=http://www.nfb.ca/film/bates_car_sweet_as_a_nut/|title=Bate's Car: Sweet as a Nut|author=National Film Board of Canada|work=NFB.ca|access-date=15 May 2015}}</ref> In 2007, an estimated 12,000 vehicles were being fueled with upgraded biogas worldwide, mostly in Europe.<ref name="What is biogas" />

Biogas is part of the wet gas and condensing gas (or air) category that includes mist or fog in the gas stream. The mist or fog is predominately water vapor that condenses on the sides of pipes or stacks throughout the gas flow. Biogas environments include wastewater digesters, landfills, and animal feeding operations (covered livestock lagoons).

Ultrasonic flow meters are one of the few devices capable of measuring in a biogas atmosphere. Most of thermal flow meters are unable to provide reliable data because the moisture causes steady high flow readings and continuous flow spiking, although there are single-point insertion thermal mass flow meters capable of accurately monitoring biogas flows with minimal pressure drop. They can handle moisture variations that occur in the flow stream because of daily and seasonal temperature fluctuations, and account for the moisture in the flow stream to produce a dry gas value.