John Crow

The source is both animal (mammal) and human. 10-100L per day is a lot to flush down the drain, and the solids are already taken care of, so I was looking for some efficient way to recover the useful components. I posted to composting forums expecting "merely" recipes and setups to convert it into nitrates, but happily the responses have been far broader than that.

One person has suggested mushroom farming/growing... apparently mushrooms can take in a substantial load of ammonia directly, unlike other plants for which substantial amounts of ammonia can be toxic. Likewise another person has suggested just pooling it and adding vinegar, producing ammonium acetate which could be crystallized and removed. Either method would be aided by the addition of some soy based urease.

On the other hand, if there's a good way to take the urea->ammonia->nitrite->nitrate path to its normal biological terminus, as I originally thought I'm all ears. I can certainly put my hands on large amounts of sawdust or other high-carbon (Is "brown" the right term here? I'm new to composting) materials.

How long does it take for N cubic meters of brown stuff at core temperature T to convert urine to soluble nitrates? Is there a formula somewhere? Or are there practical rules of thumb?

-Riventree

A little yield math:

NASA (see reference) suggests that there is 9.3g of urea, 3g of salt, and 3g of "other solubles" in a typical liter of (human) urine. It's a very dilute solution, mostly water and three fifths of the dissolved mass is urea. Wikipedia gives the molar mass (g/mol) of urea as 60.0g. That's about 1mol of nitrogen for every 3.2L of urine. (2N/urea) Wikipedia gives the molar mass of the nitrogen salts of calcium at 164g/mol, potassium at 101g/mol and sodium 85g/mol, and other similar salts in the same range.

Thus for an input of 30L (my average daily volume, above) of urine, you could receive:

* 30L of distilled water
* 1kg of nitrogen salts
* 310g of NaCl (table salt)
* and 300g of "other" (waste).

That's on the order of 2000 times less volume of waste.

The question becomes: How many hectares (or cubic decameters, or whatever) of compost would be required to absorb that much urine per day?

=References=
David F. Putnam, "Composition and Concentrative Properties of Human Urine." NASA Contractor Report. July 1971

Hello everyone. I've just begun researching composting, and I was surprised that googling "composting forum" actually came up with pages of results for forums, much less for posts on the subject, so I'm a bit overwhelmed. There is a huge body of (very dispersed) knowledge out there, but most of it seems to be oriented toward producing generic fertilizer rather than a particular set of chemical components.

Likewise, should one dare to search amazon books for "composting", there are a veritable plethora of sources. Unfortunately they too are focused on the resulting mixture and levels of K, P, Ca, and other nutrients taken as a whole.

What I'm looking for is information which can take me towards a composting system where mammal urine goes in one end, and a liquid stream rich in soluble nitrates exit the other. The other products (methane, solids, etc) are completely secondary.

I see MANY general texts, webpages, etc., out there. I've familiarized myself with a lot of them. Can anyone recommend a text, paper, webpage, or expert who might take me "the next step" toward my goal?

Thank you for your consideration,
-Riventree

P.S.

The short version of the reason that I'm doing this project is: I have a stream (no pun intended) of urine on the order of 10-100L per day, and I'd like to turn it into something useful rather than dumping it down the drain.

Ammonia is one possibility: Drop in some urease from soybeans and capture the ammonia via air-stripping. Simple, but there are two downsides: First, the volume doesn't change much (urine -> NH4(aq)) Second, leaks are smelly.

On the other hand, if I can further bioconvert the urine/ammonia to nitrates, those can be dried and transported easily, and have no odor in the case of a leak in the system or the transport.

Please keep the ideas coming! I'm open to any suggestions out there, in terms of chemistry, physical setup, "right" compost mix, temperature, etc.

All help welcomed thankfully
-Riventree