Research ignites lethal secrets of personal slurry

If you thought flatulence was all noise and hot air then think again. There is a wealth of science associated with your average gaseous emission, and a researcher at the Institute of Technology Sligo has all the details.

Dr Declan Shelly in the Department of Applied Science had his audience on the edge of their seats last night in Sligo with his talk, "Flatulence and the Common Man". It is one of a series of public lectures staged this week by Sligo's IT as part of Science Week Ireland.

Dr Shelly regaled his audience with a range of facts and figures about the four-letter "f" word. The average person discharges about 400 cubic centimetres of gas a day, he told his incredulous audience. Some people released a mere 200 cubic centimetres per day, but other generous souls were capable of emitting up to two full litres of gas in a single day.

Clearly, these are just the sort of people to avoid if at all possible, and not just because you run the risk of getting blamed in the wrong for the noise or the odour.

One main constituent of human produced gas is hydrogen sulphide, a highly toxic gas also given off by slurry, Dr Shelly explained.

It was a comparatively simple matter to determine what gases were included, he said. A typical sample contains hydrogen, oxygen, nitrogen, methane and the nasty hydrogen sulphide. Much more challenging, he added, was calculating the weight of a typical emission.

He used Avogadro's Law as part of his calculations to work out a figure. He clearly impressed his audience with the news that a typical discharge involved about 40 cubic centimetres of gas and, based on certain assumptions about content, this weighed a dainty 34 milligrammes.

What a typical discharge lacks in weight it makes up for in molecular content, and this same emission included no less than 10 to the power of 21 molecules of various types. This huge number is 10 followed by 20 zeros, Dr Shelly explained.

The fastest computers would take 200 million years to carry out a similar number of calculations, he said. So there, you computer anoraks.

"These are real medical facts, not just off the top of the head," Dr Shelly added. He also considered the sound associated with this activity. "The force that it is extruded with is the key thing," he noted.

He finished his lecture with a pyrotechnic flourish, burning off small amounts of a key constituent, methane, just to show that, yes, they really do light. He pointed out, however, that he had used pure methane and not actual samples collected from volunteers.

While the lecture might have been tongue-in-cheek, its goal was much more serious, he admitted. "It is trying to get people interested in doing science."