I was browsing all around for drawings of the various ways to build human waste composters. They made sense and were well designed (wish I saved the URL), except for one. It had separate holding tanks for the solids and the liquid. There was no explanation. Do any of you know why one would keep the urine separate?
The functional reason I see for this is to make handling the fecal matter easier. However, I respectfully disagree with the logic for this because one could design the toilet in such a way that there is a constant draft (up or down depending on preference) which will aid evaporation of excess water. If the composting is going on inside the toilet, I think the water from the urea would aid decomposition. That is why I am a little confused on why it would be necessary to seperate the urea from feces. Unless, of course, the urea is intended for dilution and watering in the garden. Then, it kinda makes sense.
Which composting toilets have you been reading about?
I haven't refreshed myself on my biology and chemistry, yet (probably should), but if I remember correctly, fecal matter usually contains phosphorus and whatever is left over from digestion. Then, urea contains nitrogen (in the form of ammonia?), salts, and used water. I still do not see a problem with mixing the two.
The quote below gives you at least three reasons for separating urine
"At the time when latrine contents were collected in buckets from each household in Swedish
cities, urine was often collected separately and poured into the drain to avoid smells and to
prevent the latrine from filling too quickly (Sondén 1889). Already in 1867 it was known that
“the proportion of value of the fertilising ingredients held in solution in urine to that contained
in faeces is as six to one”
Roger, there are different schools of though out there. Joseph Jenkins of the Humanure Handbook recommends mixing urine and faecal, so that the nitrogenous content of the urine deals with the carbonaceous sawdust in the compost pile. The Dutch Nonolet unit that I use here in Ireland separates the two, which means that I can compost the faecal in a vermicompost system in a sealed plastic compost chamber (a friendly solution in a suburban garden) and then use the urine which is biologically cleaner on a comfrey bed for a quick return on the N, P and K.
Whether to separate or not depends on the system you are using. The Humanure Handbook and EcoSanRes resources are both given as links on http://www.wetlandsystems.ie/watertips.html if you want a closer look at the subject.
My take on it is that urine is a valuable fertilizer, much safer for general use than humanure. If it's fresh and from a healthy person, it can simply be diluted four or five to one and used directly around growing plants, or else used undiluted onto planting beds before planting, as a sidedress around nitrogen hungry plants before an irrigation or rain, or as a pick-me-up for composts of all sorts. I have grown many a crop of corn, wheat, and other things with the only soil amendment being urine, and am of the opinion that containerizing urine and using on the land is one key to ratcheting up productivity on a small homestead. Humanure, on the other hand, needs long and laborious processing to make it safe, or is only suitable for certain niches; whether or not the urine is mixed into it.
Alder Burns wrote:My take on it is that urine is a valuable fertilizer, much safer for general use than humanure. If it's fresh and from a healthy person, it can simply be diluted four or five to one and used directly around growing plants.Humanure, on the other hand, needs long and laborious processing to make it safe, or is only suitable for certain niches; whether or not the urine is mixed into it.
I wouldn't use humanure in food production. Ornamental only.
Pee alone in liquid gold.
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Alder I would not call humanure composting a long and labourios job or chore and if done correctly humanure is food grade compost. You are correct that it is a long process compared to the immediate use of urine and separating urine works well for some people. A humanure system does take some labour as does planting a garden, sorting recyclables, having compost of any kind and everything worth doing in life. You make it sound like a life sucking drain on someones existence and I have not found it to be that at all.
Life is too short or my list is too long, not sure which.
I prefer separating the two because too much liquid creates sludge, and that's the opposite of composting. Different times of the year create different reactions down below, and it's safer, and more agreeable to handle, when the liquid is controlled. I don't use any kind of fan to dry things out, just as I wouldn't in a compost pile in the garden.
It only takes one weekend of company, even two other people, sitting around drinking any kinds of liquids in a social situation to upset the balance. Holidays with lots of extra people who don't understand the situation can make life miserable for months to come.
Since I am the person in control of the composting, I know the signs of too much or too little liquid, and it's very easy to keep it on an even keel. I am a real fan of urine for nitrogen in the garden, and we're not so much controlling urine as we are harvesting amendments for the plants, which gets used right away, no reason not to let it starting working in the soil or saturate wood for hugelkultur pits
Don't fall for the My-Place-Is-Special, It-Won't-Happen-Here Syndrome.