# Is a fart just a fart or is there more to it?

**URL:** <https://boards.straightdope.com/t/is-a-fart-just-a-fart-or-is-there-more-to-it/917041>\
**Category:** In My Humble Opinion\
**Created:** [August 2, 2020, 3:14am UTC](https://boards.straightdope.com/t/is-a-fart-just-a-fart-or-is-there-more-to-it/917041 "2020-08-02T03:14:08Z")\
**Posts on this page:** 3\
**Page:** 2

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**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\
**Post date:** [August 24, 2020, 1:40pm UTC](https://boards.straightdope.com/t/is-a-fart-just-a-fart-or-is-there-more-to-it/917041/21 "2020-08-24T13:40:46Z")

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When I was a kid, my dad’s euphemism for fart was ‘let wind’; as in, ‘Did you let wind?’

Just had to get that out.

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**Author:** ![rboyce](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rboyce/32/4066_2.png) [@rboyce](https://boards.straightdope.com/u/rboyce)\
**Post date:** [August 30, 2020, 5:54pm UTC](https://boards.straightdope.com/t/is-a-fart-just-a-fart-or-is-there-more-to-it/917041/22 "2020-08-30T17:54:56Z")

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Most large sewage treatment plants use a two-stage digestion system in which organics are metabolized by [bacteria](https://www.britannica.com/science/bacteria) anaerobically (in the absence of oxygen). In the first stage, the sludge, thickened to a dry solids (DS) content of about 5 percent, is heated and mixed in a closed tank for several days. Acid-forming bacteria hydrolyze large molecules such as proteins and lipids, breaking them into smaller water-soluble molecules, and then ferment those smaller molecules into various fatty acids. The sludge then flows into a second tank, where the dissolved matter is converted by other bacteria into [biogas](https://www.britannica.com/technology/biogas), a mixture of [carbon dioxide](https://www.britannica.com/science/carbon-dioxide) and [methane](https://www.britannica.com/science/methane). **Methane is combustible and is used as a fuel to heat the first digestion tank as well as to generate electricity for the plant.**

> **[Wastewater treatment - Sludge treatment and disposal](https://www.britannica.com/technology/wastewater-treatment/Sludge-treatment-and-disposal)**
>
> The residue that accumulates in sewage treatment plants is called sludge (or biosolids). Sewage sludge is the solid, semisolid, or slurry residual material that is produced as a by-product of wastewater treatment processes. This residue is commonly...

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**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\
**Post date:** [October 9, 2020, 7:07pm UTC](https://boards.straightdope.com/t/is-a-fart-just-a-fart-or-is-there-more-to-it/917041/23 "2020-10-09T19:07:52Z")

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Pardon the bump, but I’m staring at a BloombergNEF report (no link, sorry) pegging wastewater gas at $8-26/MMBTU, compared to ~$4 (citygate).

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