I'm talking about this as someone who is only learning, and I'm pulling most of my knowledge from 'The humanure handbook'. I don't have much experience yet, only presenting the theory.
The compost toilet is a system of recycling human waste into fresh compost, used to fertilize gardens. If done correctly, it's sanitary, odourless, and safe for human health and population.
Here are the pros: If you own any land, it's free to do, you don't need a septic tank, you waste zero drinking water for toilet use, you gain valuable fertilizer for your garden, you don't pay for your waste to be stored or sanitized, you do zero damage to the environment. Cons: you have to learn how it works, and put in some effort to compost it.
So how does that look in practice? You have a system of collecting waste, and a protected compost pile where you empty it out in order to have it composted. The way it's made sanitary and stink-free is with the addition of organic material the waste is suspended in. It's never piled on top of each other or visible, but always covered in something like sawdust, peat moss, dry leaves, grass clippings, hay or straw.
The most common thing people do is install a nice wooden board with a toilet seat in their homes, and put a big bucket under it to collect the material. The bucket can be lined with newspapers, and the bottom is always covered with organic material. Every time the toilet is used, instead of flushing, organic material is piled on top and it covers all the smells and visuals. I can confirm it doesn't stink!
Once the bucket is full, it's carried to the compost pile. Here's where some initial effort is needed.
In order to safely compost human waste, you need to build (or procure) a composter. This is easy, you only need 4 walls, the bottom is the ground, and you need to cover it with something like a net or a wire, so animals can't get to it. It can be made out of wood, metal, bricks, plastic, whatever is available. The top should be exposed to rain. Once you have that, composting it is just like any other compost pile.
If you've composted before, you know you need a balance of different materials to make a functional compost pile; that goes for this too. The bottom should be covered in organic material, the contents of the toilet added on top, also suspended in organic matter, and then covered with light organic material. It can be hay, straw, leaves, grass clippings, garden leftovers, whatever you'd add to a normal compost pile. You don't need to turn it, because the entire mass should be airy and with access to oxygen. Then you keep adding layers of human waste and organic matter until your composter is full, and leave it to safely decompose for 2 years, only water it sometimes if it gets dry. After that period, you should find fresh humus you can use for gardening. During the curing period, you fill up another composter and you alternate between the two.
The process of how this works is described in detail in the humanure handbook; the compost pile will heat up and thermophilic bacteria will thrive in it, killing all the viruses, pathogens or anything that could be infectuous or harmful to humans. This should last for a few months, then the pile cools back down and another type of bacteria will take over the decomposing process. The worms from the ground come in to help too. The author claims this is so effective it can neutralize diseased animal corpses, nuclear waste, and most other dangerous substances; I'm not sure I believe that. But it makes sense we can compost human stuff, we use cow manure, we compost the feces of any other animal, we're no different.
I haven't found a better resource than the humanure handbook but I'd be very happy to read anything written by women about it. The male author alternates between giving you instructions and complaining about everything that happened in the history of time, it's annoying, I don't trust him. But I'm going to try the compost toilet and hopefully get some fertilizer!
An important safeguard to know is that human waste should never be anywhere close to a fresh water supply, having it mixed with water is what caused the plagues like cholera in the past. Compost toilet should not be close to any body of water, or having water run from it. It also needs to be protected from animals because they will spread it around, again contaminating water.
Storing, managing and purifying human waste is an industry that costs a lot of money, takes a lot of resources and does damage to the environment. We are constantly paying for our waste to be dealt with, flushing drinking water with it, and getting nothing out of it.
We have the knowledge to handle it safely, we know better than to mix it with our water supply, and we could restore our soil fertility with it, something we are quickly losing. If you can give it a try, it's free. It doesn't stink. There already are facilities that do this for money and sell the humus. So it's been tried and true. We should be smart enough not to get icked by our own crap.