Sarah DeWeerdt's recent article tells of how "Gerardine Botte, a professor of chemical and biomolecular engineering at Ohio University … has developed a technology to generate hydrogen fuel from urine".

Urine has, in fact, had an impressive range of practical uses for much of history. A key area was medicine. In Rome, Pliny the Elder recommended fresh urine for the treatment of "sores, burns, affections of the anus, chaps and scorpion stings", while stale urine mixed with ash could be rubbed on your baby for nappy rash. In early-modern Europe numerous medical luminaries went further. Pioneering French surgeon Ambroise Paré noted that itching eye-lids could be washed in the patient's urine – provided that it had been kept "all night in a barber's basin" first. The father of chemistry, Robert Boyle, advised certain patients to drink every morning "a moderate draught of their own urine", preferably while "tis yet warm". Anyone indignantly demanding a second opinion would find that Thomas Willis – the richest doctor in England at the time – was instructing a young gentlewoman to drink her own warm urine against "extreme sourness" in her throat.

Other cases could be far more urgent. In about 1550 the Italian doctor Leonardo Fioravanti saw a man's nose sliced off in an argument, and promptly urinated on the fallen organ before stitching it back on. Henry VIII's surgeon Thomas Vicary recommended that all battle wounds should be washed in urine; and others advised the same for potentially gangrenous ulcers, or poisonous bites and stings. Being sterile when it leaves the body, urine was then a far safer cleaning agent than the kind of water typically available.

Forms of processed urine could be used in no less desperate situations. In 1666 the physician George Thomson was recommending it against the plague; and over in France in 1671 the chemist Matte la Faveur was patiently collecting vast quantities of unadulterated child's urine ("about sixty pints [from] little children who drink very little wine") to make a volatile salt from it. Such advanced therapies were of course not for the humbler sort. On 13 June 1685, for example, we find Madame de Sévigné telling her daughter of how, "for my vapours I take eight drops of essence of urine".

Boyle, who performed numerous experiments with human blood and urine – including using both as invisible inks – noted how the latter was highly valued by dyers; while the historian Dominique Laporte reminds us of its popularity for the cleaning of hats in France. Then we have cosmetics. The Elizabethan surgeon William Bullein advised those "whose faces be unclean" to wash their skin with "strong vinegar, milk and the urine of a boy". In 1675 The Accomplish'd Lady's Delight in Preserving, Physic, Beautifying, and Cookery told of how one's own urine was "very good to wash the face withal, to make it fair". Compare the northern Scottish author Mary Beith, who (writing in 1995) emphasises that, "today, urea remains an important ingredient in medicinal skin creams", also recalling "babies having their faces wiped with their own wet nappies" by way of skin care: "a friend of mine with four boys made a virtual religion" of this, "and not one of those boys became a spotty teenager". (Anyone who remains unconvinced may like to bear in mind that Roman women were known to beautify their cheeks with human excrement, while those afflicted by smallpox in later centuries could fill the pits with a mixture of human fat and beeswax.)

Cases of plague or serious wounds remind us of how historical context can radically alter one's disgust threshold. Compare, too, those soldiers of the first world war who used cloth patches soaked in their own urine as rudimentary gas masks (the ammonia in the urine counteracting the chlorine in the gas). In The New Confessions, William Boyd's errant hero, John James Todd, has a memorable experience of this when, as night sentry, he yells a gas warning and produces a collective deluge of urine (and urine-damped faces) – only to then find that he has actually sighted nothing more poisonous than a drift of thick mist.

Those of us who live long enough may find that the urine-powered car is an essential piece of technology in the age of rising fuel costs and melting ice-caps. Vehicles have already been run on chip fat, for example. Moreover, in November 2008 the Beverly Hills surgeon Craig Alan Bittner suddenly closed his thriving liposuction practice and fled to South America. Why? Bittner had been using the extracted fat of patients as "lipodiesel" to fuel the SUVs of himself and his girlfriend, and was therefore violating state laws on medical waste. Perhaps one day drivers won't stop to use the toilet, but use the toilet so that they don't have to stop at all ...