What could make a glass of beer better than a jigger of stale urine?
Urine is mostly a sterile solution of nitrogen-rich urea in water. Urea is useful enough in itself; last week I got a packet of yeast nutrient for my homebrewing, and it was (artificially produced) food-grade urea. It's an agricultural fertilizer also, and a flavor enhancer in cigarettes. But as bacteria enter and ferment the urine, the lant sours with hydroxide ions and the urea decays to ammonia and carbon dioxide.
Ammonia was essential enough to Roman and medieval European societies that ordinary people were expected to save their urine to be contributed to the communal town piss-pot. Washerwomen collected the lant for cleaning clothes, tanners for preparing leather for tanning, dyers for producing indigo dyes, textile makers for use as a mordant on wool. The Romans knew it to be an excellent mouthwash, for whitening the teeth.
Lant is also essential in the preparation of saltpeter (potassium nitrate) for the manufacture of gunpowder. To make saltpeter, prepare a large nitre-bed of a porous material such as straw, earth and manure, along with wood ashes. Wood ashes are important, as in the way they are used with lime to make lye for food processing and soap. Cover it from the rain and keep it moist with urine; let this age for a year or so. Run water through the bed to leach out the potassium nitrate, and run this liquor through the bed several times until you can float an egg in it ( 1, 2, 3 ).
Indeed. Lant is useful for many purposes, from beverages to laundry to alchemical rocket engines.