Beginning with the end in mind

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

Aquaponics does something similar.

They often use urine to kickstart the process.

Urine is diluted in a large volume of water, say 1000l, it is then pumped into a waterproof bed filled with gravel or something else with a high surface area. Bacteria on the gravel converts the urine to nitrites and then other bacteria converts it to nitrates. Once nitrate production is up and running they plant leafy greens in the gravel bed, which flourish with all the nitrates. The cleaned water is then returned to the water tank, in the case of aquaponics they keep fish in the freshly cleaned water and the fish provide the ongoing ammonia to fuel the plant growth.

The cycling as it is called can take weeks to months depending on local conditions.

I guess if you don't mind running a pump to keep the urine circulating then it might work out quite nicely. You would not be exporting the nitrates though and I guess if the urine is from warm blooded animals then you might have to worry about pathogens in the food.

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

Hey John, welcome to Permies.com.

Your project is not quite in the permaculture realm, but it's not entirely outside either.
As I understand it you want to develop a refined chemical product? 10-100 liters is not a huge amount, sounds like a cottage industry.

A natural method of treating mammal urine would be to compost it with high carbon materials: leaves, hay, sawdust, paper, with the end product being used for soil amendment. If you are talking about humans as the mammal, I invite you to browse the forums, it is discussed at length.

Mammal wastes, be it from cities, feedlots or other high density livestock operations is a considerable problem. The folks around here come up with some pretty amazing ideas, most often with natural processes in mind. After all, it is a permaculture forum. I hope you find what you are looking for.

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

Don't flush it down the drain! It's all perfectly good fertilizer. Dilute it 1:1 at least with water and spread it on yours and all of your neighbors' gardens. Or fertilize a large composting operation that has lots of woody mass, it'll help break it down.