Brief History H.M. Rouelle in 1773 discovered Urea in human urine. It was synthesized in 1828 by Friedrich Wohler. Here is where the organic gardener and the chemical gardener part ways. In 1870 urea was produced by heating ammonium carbamate in a sealed vessel. This provided the basis of the current industrial process for its production.
Ammonium carbamate is obtained by direct reaction of ammonia with carbon dioxide.
These reactions are normally carried out simultaneously in a high pressure reactor. The whole idea is that there is a difference between an organic source of nitrogen and a chemical source of nitrogen. This is still the current logic that chemical companies would like you to believe. The American idea that a little is OK but a lot is better does not really apply here. Another good reason most people do not use animal or human urine is health concerns although animal or human urine is perfectly safe to use as long as the donor is healthy.