Gulp by Mary Roach

Author:Mary Roach [Roach, Mary]
Language: eng
Format: epub
ISBN: 9781780742199
Publisher: Oneworld Publications

12

Inflammable You

FUN WITH HYDROGEN AND METHANE

LONG BEFORE ANYONE put a cautering wand up anyone else’s bum, the dangers of flammable81 bowel gas were well known. If you let manure sit, as any farmer can tell you, bacteria will break it down into more elemental components. Some of these are of value to farmers as fertiliser, which they can pump from their manure pit out onto their crops.82 Others – hydrogen, say, and methane – will blow the roof off the barn. Here is the Safe Farm programme channelling Beatrix Potter in a methane-safety radio spot: ‘It has no smell. It has no colour. It often lurks about, but fails to leave a trace’.

Methane and hydrogen are explosive in concentrations higher than 4 to 5 percent. The foam on liquid manure in pits is 60 percent methane. Farmers may know this, but their families sometimes don’t. Which explains why the University of Minnesota Extension Service’s farm safety curriculum includes instructions for a children’s classroom Manure Pit Display. (‘You will need:... toy cow, pig, and bull [1/32 scale], an aquarium, one pound of dry composted manure... and chocolate [chips]... to simulate manure on top of floor [optional].’)

Like a Manure Pit Display, the human colon is a scaled-down version of a biowaste storage tank. It is an anaerobic environment, meaning it provides the oxygen-free living that methane-producing bacteria need to thrive. It is packed with fermentable creature waste. As they do in manure pits, bacteria break down the waste in order to live off it, creating gaseous by-products in the process. Most voluminously, bacteria make hydrogen. Their gas becomes your gas. Up to 80 percent of flatus is hydrogen. About a third of us also harbour bacteria that produce methane – a key component in the ‘natural gas’ supplied by utility companies. (At least two-thirds of us harbour a belief that methane producers’ farts burn blue, like the pilot light on a gas stove. Sadly, a YouTube search unearthed no evidence.)

The flammability of methane and hydrogen is part of the reason for the seeming overkill of protracted bowel-cleansing that precedes a colonoscopy. When gastroenterologists find a polyp during a screening, they will usually remove it while they’re in there, using a snare with an electro-coagulating option to staunch the bleeding. They do not want to worry about igniting a rogue pocket of combustible gas – as happened in France, in the summer of 1977, to fatal effect.

At a university hospital in Nancy, a sixty-nine-year-old man arrived at the Services des maladies de l’appareil digestif (French for ‘gastroenterology department’). With the current set to 4, the doctor began a simple polypectomy. Eight seconds into it, an explosion was heard. ‘The patient jerked upwards off the endoscopy table’, reads the case report, and the colonoscope was ‘completely ejected’ (French for ‘launched from the rectum like a torpedo’).

What was strange was that the Frenchman had followed his colonoscopy prep instructions to the letter. The culprit, in this case, had been the laxative. The staff had prescribed a solution of mannitol, a sugar alcohol similar to sorbitol, the likely laxative agent in prunes.

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