Today as I was growing impatient in my wait to hear back from my request for information on the 3-hole ecosan pan and western style designs, I thought I'd go about attempting to build something similar from materials I have around here at least to get a proof of concept that wouldn't be as pretty or durable but would work. The first thing I thought would be important to know is a good diameter of the number 2 hole because that diameter would dictate the necessary diameter for the funnel apparatus that would be operated by a lever to close off the number 2 chute and provide diversion for number 3 (bottom wash water). So I pulled up google with as is often the case, search terms that don't take me directly to an answer to the particular question I am pondering. Instead, I may have found something even better as in an overall better design for diverting urine reliably from solids. It relies on the Coandǎ effect which is the tendency of fluids to adhere to a smooth surface. Urine is transported along this surface until it is far enough out of the way of where #2 is falling and it reaches the end of the surface which is conveniently located above a gutter. The advantages of this design are it's ability to perform it's separating duty for all ages and genders without becoming clogged. I imagine there would still be the possibility of contamination of the urine with fecal matter in cases where the solids were of a more wet and/or sticky consistency since some might stick to the separating plate and later be washed off by and carried with some urine. I don't believe the potential contamination of urine is at all unique to the design. [DON"T read between the parenthesis.] (The only design I can imagine that might be capable of keeping the urine completely pure would be a complicated design involving an artificial intelligence who could accurately position the urine funnel(s) to catch every drop even in cases where a male was standing and writing letters with his stream. Of course that would require sensors of some sort, probably cameras and somehow I don't see that going over too well with anyone, not to mention potential problems with high speed funnel movements.)
For me the main disadvantage of the NatSol design is that it appears to only be designed for sitters and wipers, and not for squatters and washers. It should be entirely doable to modify the design to accommodate both. I suppose If you and I are the ones doing the design modification we could potentially at least partially avoid the other disadvantage being the high cost of the commercial units.
Here we use dry composting toilets, and we have perennial discussions about urine separation. Because it is a residential school with a lot of turnover of visitors, volunteers, and guests, as well as students who change every year, I am strongly in favor of keeping it simple. We use sawdust/shavings as the cover material for much of the year, so the moisture is helpful anyway. If we removed all of the urine, we might end up 2 years later with desiccated feces in a pile of dry sawdust, instead of compost. But sometimes it does get too wet. Having a stand-up urinal for men going into a storage barrel is just the right balance -- enough urine goes into the sawdust-feces chamber to keep it damp and composting.
What I like best is that it is foolproof. A urine separation seat or pan has a terrible tendency to be misunderstood by visitors, who then occasionally foul it up, creating a disgusting or embarrassing situation for one or more people, and inconvenience for more. You'd be amazed by the myriad ways that people can misunderstand (or wilfully misuse) a novel type of toilet. Nobody will ever accidentally poop in a familiar wall-mounted urinal and contaminate the urine.
It might not be appropriate for your situation, but for our situation I think it is much better than separation pans / seats. But we have these discussions here over and over again, and some here are very keen to try separation seats.
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.
Writing letters with one's stream is more properly done in a snowbank, so you can see the product afterwards. Now that's urine diversion. No plates, no funnels, no camera, and no creepy camera-enabled AI for me to pee on, watching me.
I think you've raised an interesting point, Rebecca. This is another area, I think, where people, being people, have latched onto this idea that they must divert all urine from feces. We forget that the place of reasoning from which this all started is that too much urine in the mix makes things go anaerobic, feeds pathogens, et cetera.
That doesn't mean that it is necessary to have a system where no urine makes its way into the fecal composter. It's necessary to monitor and regulate humidity and levels of aeration, such that the mix gets enough air to keep from getting anaerobic.
I was actually thinking about this from the other end of things, as a somewhat less-practical proof-of-concept. What if we had a number of 55 gallon drums all set up to swirl their liquid contents in a reversable vortex via pump, all connected for volume, aeration, and capacity, and probably using bubblers, too? And what if there was a receiving drum that was fed by low-flow toilet, no urine diversion, no nothing?
Now the system would have to be set up and charged, essentially filled with the makings for a good and potent actively aeratedcompost extract, and set up as an aerated liquid composter, such that when the feces hit the circulating system (no fans, thank you, unless our solar chimney idea needs a little boost), they get rapidly and completely devoured, pathogens and all, by the roiling, swirling, bubbling froth of beneficial biological activity.
If I were to attempt this, I think one container would be better, but depending on scale, that might be two IBCs, one for active biological processing of fresh contributions, and a second stage, same as the first, that continues to swirl and bubble in conditions best suited for beneficial soil bacteria, with a valve at the bottom to allow for withdrawals, or direct connection to a fertigation setup, even if just for my woodlot and windbreaks.
Don't get me wrong. This is a thought experiment. I don't like macerating pump-based toilets because of what happens if and when they fail, and that would be the downfall of this system, too. But if, for instance, such an aerated compost extract bioreactor for fecal composting sped up the process, and ensured no possibility of pathogenicity in the end-product, the benefits might, indeed, outweigh the added hassle.
Of course there's nothing wrong with mummifying feces in sawdust or whatever. The pathogens die if they dessicate, so mission accomplished, sort of?
Oh, and does anyone know how the poop reclamation projects up at the lab are doing? Don't they have many barrels of aged poop just standing there? I wonder how they turned out?
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects.
-Robert A. Heinlein
I agree that some amount of urine going into the feces is no problem and in fact desirable from a composting standpoint. What I believe has been discussed on this forum is the need to keep the urine pathogen free so it can be used safely for fertilizing.
I've owned two of the Sun-Mar "composting" toilets and ended up going back to a Jenkins style that I later added a home-built funnel type urine diverter which worked reasonably well to keep it aerobic and reduce trips to empty the bucket.
It wouldn't work everywhere, and it fails to work at all in certain weather or seasons, but I really like my "dung beetle feeder". It took nothing to construct although one could upgrade it with a privacy screen or wall if one has neighbors. The dog uses one too, just squat down and if not immediately, the dung beetles fly in and take care of things. If they don't then a shovel and some soil takes care of things to keep it from becoming a fly nursery. I wonder how great a potential for contamination of garden veggies there might be with a dung beetle feeder.
Granted it takes a greater initial investment of time/money/materials, but the two (or more) vault true composting unit does seem the way to go. If the time/money/materials for a vault system and a bucket or roll-away system were all converted to time for ease of comparison, I suspect sooner or later the seemingly less expensive bucket/container system would overtake the cost of the vault system.
The aerated liquid idea sounds interesting but certainly not terribly simple. Potentially could make a super safe fertilizer.
My opinion is that adding complexity to a system adds to the chance of failure. I used a Jenkins humanure type system for two years with no separation of products and it worked very well. I'm a big proponent of the KISS principle when possible.