Remember that the carbon-to-nitrogen (C:N) ratio of urine (8:1) is too low for microbes to use and fully break down into a plant-usable form. To preserve all the fertilizer value of urine, a carbon-to-nitrogen ratio of 25:1 is needed to convert all the nitrogen to nitrates by aerobic soil bacteria. (Again, nitrate is the form of nutrient that plants use best.)

But that would require loads of high-carbon materials such as wood chips, peat moss, and so forth. Most of us are not on a farm that could provide enough straw or leaves from trees for this purpose. And, remember, that the primary use of additives is to provide pore spaces for air, not to provide carbon.

Instead of adding a room full of sawdust (C:N 400:1) to a year’s worth of urine to achieve C:N 25:1, consider adding some more concentrated forms of carbon, such as sugar.

Why add sugar to a urine composter? Sugars are the most “available” of all carbohydrates and can provide a lot of carbon with little volume compared to straw, leaves, and wood chips. These are primarily difficult-to-digest celluloses and lignin that, in a composter, are decomposed by fungi and actinomycetes – not by bacteria.

Sugar, however, is a simple carbohydrate. Adding some cane sugar might not seem ecologically elegant, but it will surely adjust the C:N ratio, in place of a truckload of sawdust. About a third of a cup of sugar per person per day should do it. Diverting and using urine might seem on the “lunatic fringe” now, but the benefits of doing so are hard to ignore, and it will be a “common sense” practice in the future.