A minor point worth considering in this discussion is that the accumulative effects of many (most) in the population contributing substances they may not realize have enduring effects in the environment, could be as significant as one person using a certain drug for a short period. On the small island where I live, our primary
water source for the community (those not on
wells), a 'pristine' and fairly remote lake among the forests, was tested for the degree of (unauthorized) swimming affecting water quality. The levels of residues - principally hormonal compounds from birth control pills and also caffeine - convinced the community, regretfully, that the entire lakeshore area had to be fenced to prevent the uncontrolled degree of escalating public use of the lake, largely by off-island campers and visitors who, I guess, had never thought of holding their
pee until away from the lake. The accompanying fire-risk to both lake and forests clinched the decision, despite the great expense.
I imagine most folks would not even consider
coffee and the pill as likely to go further than their own digestion, but the fact they are both present in measurable concentrations despite massive dilution tells us something about even lake-scale environmental bodies, when an entire population is routinely ingesting these two very common substances. I guess we have to consider pretty much everything that we ingest not strictly for nutrition but rather for its EFFECT on the body, as being worth taking into account after leaving our tail end too.
I have run a household scale composting-toilet system in my family's home for all our
humanure needs for 37 years now, using a SunMar central composting unit (Centrex 3000 currently) from two bathrooms on floors above. It has a large rotatable composting chamber, and rotation causes the material to move progressively along the horizontal drum until it exits into "The Doghouse" - a sizable bin, which can then be emptied into my enclosed dedicated composting bins a few times a year. Apart from poo, pee and toilet paper, the only addition is small amounts - a few cupfuls - of chopped hemp stalk (CompostSure) every few days into one or other of the very-low-flush toilets (Dometic SeaLand units). The system can handle regular household use by 4-6 people, or occasional use by up to say 10-12, since it has a sufficient mass of material that it's not subject to the same swings as a small unit, particularly fluid excess, which can all too easily happen.
To have a system that doesn't demand any handling or turning of the waste or constant maintenance is worth a lot in terms of quality of life, believe me - after a long involvement with these processes, I'm happy to have a system sufficiently oversized for my needs that reduces stresses and greatly extends how well-composted the material will have become by the time it emerges from the chamber. Slow ageing at cooler temperatures year-round ensures that waste is totally inoffensive (to me, at least) by the time it gets dug out of the hatches at the base of my garden
compost bins. In total that might be a couple of years, in the drum, in the doghouse bin and in the garden compost bin
To ensure a high degree of confidence about the safety of the composted waste, my humanure waste stream continues breaking down in separate compost bins from my normal garden+kitchen compost stream, enabling me to choose and assess what and when to put on food plants, what on flower beds, and on the
native plants I raise for pollinators and Garry oak habitat restoration.
Key elements for a system like this are a) to limit the liquid input, which can otherwise be problematic if you need to deal with waste from more than one toilet, requiring a small amount of flush to transport it to the central unit. My system now uses no more than about a cupful or so of water per flush; b) limit carefully what guests and others put into the system beyond human waste and TP - tampons, pads, wipes, cigarettes!, toys, recycling, plastic - no, please, really no; c) excess liquid leachate from the chamber needs a constant piped route to a properly-sized, dedicated, evapo-transpiration bed (SunMar website offers a sample design). For years I relied on a French drain soakaway type of pit, and only realised how inadequate that was by the changes/damage to nearby
trees, moss-beds and shrubs. I'm on near-bedrock, ridgetop
land, which exacerbated that issue, but it seems to be a common problem in many places, if there's no reliable way for excess fluid to be taken up and sequestered by plant growth. It needs to work in all seasons of
course, from snow to baking heat.
'Hope some of this is useful to someone in this wonderful permies community.
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