The Set-up: Before we dry-walled the house, we ran a vent for the composting toilet up through the wall and out the roof. The top of the vent is just above the roof line, which helps keep the air pressure at the top of the vent lower than the air pressure in the toilet, creating a natural vacuum for the odor. At the bottom on the toilet is a tube which drains excess liquid. We ran this tube through the wall to the outside of the house, and into a gravel-filled infiltration pit. It would be much more difficult installation were we installing it into a pre-existing house, because it required access to the inside of pretty much the entire southern wall of the house, but as it were, it didn't take us more than a day. The only other detail was making sure we had an electrical outlet where the toilet would live, to run the tiny fan that helps the vent remove smells.
Use: There's been a learning curve to using a commercial composting toilet. For the last two years we've been using the five-gallon-bucket-approach, which while it has it's fair share of downsides, is a very simple thing. Christy and I, being the designers and builders that we are, have a harder time adapting to someone else's idea of how a thing should work than we do making something the way we think it should work. I could build just about anything in half the time and with half the frustration it would take me to assemble an Ikea kit. It's ridiculous, but true. With these shortcomings of ours in mind, I'll tell you about the breaking in period.
Our first problem was a smell. Specifically, the smell of urine. Throughout the house. It was horrible. We tried tilting the toilet back towards the wall, hoping that more excess liquid would drain through the tube we ran out the wall, which helped. I started peeing outside. We cleaned the "evaporation chamber", which indeed was caked in dehydrated urine the consistency of bacon grease. (Sorry if that's graphic, but you are reading a blog post about a toilet) It was gross. After a few days, the smell diminished. The going theory, because we never found a silver-bullet to the problem, is that in the very beginning there wasn't enough established compost to absorb the amount of liquid, which left an excess in the evaporation chamber, which smelled so bad that even with the electric fan couldn't get rid of it all. We've noticed the smell a couple of times since then, and it's often after we've had house guests, which supports the theory that the compost-to-liquid ratio is critical to avoiding odor.
Every other day, the compost is tumbled by turning a handle which rotates the entire internal drum. This has become habit, we don't even think about it. By rotating it routinely, and always using a cover material (either peat-moss and wood shavings, or compost from our garden pile) after bowel movements, there is no feces smell, which was a constant problem with the five-gallon-bucket. I can't tell you what a joy that's been for us. The overall grossness factor of this toilet is pretty much nil.
Emptying: Christy and I, who share everything well and don't have any need for "I did this last time" sorts of conversations, kept very good track of who last emptied the five-gallon-bucket. For even the least fecophobic amongst us, that was a harrowing chore. Not only was the odor overpowering, but the bucket was heavy and the compost pile was dozens of yards away. And then there was the cleaning of the bucket! Whew! Thank god those days are behind us. I emptied the finishing drawer of the composting toilet for the first time a few days ago. We waited too long to empty the compost drum into the finishing drawer, and the drum was starting to get too full. We've since figured that these each need to happen about once a month, which means the finishing drawer gets to sit for a full month. The finishing drawer had only been sitting for a week when I emptied it with extreme trepidation. What was going to be in there?
I was shocked. It looked like dense, damp, loamy soil, but with a dead octopus in it. I stared at the dead octopus for a full minute until I realized that it was a mushroom! There were mushrooms growing all throughout it! At this point I took a deep whiff of the drawer, and yes!, it smelled like mushrooms. Not a hint of anything foul. Mushrooms are a large part of the macrobiology involved in composting waste, and I take the thriving ecosystem I found as a very good sign of our toilet's composting abilities. Not only was it bustling with macrobiological life, but the drawer was warm to the touch. Hot really. What this tells me is that we have the beginnings of thermophyllic composting taking place. This is the composting process that most safely kills off human pathogens, and is the goal of humanure for garden use.
I emptied the finishing drawer into our garden compost pile, in hopes of encouraging that thermophyllic composting. To be extra safe, that compost pile will sit for at least a year before we use it in the garden, but I'll be taking note of it's temperature, to see if we are getting the best of both worlds, humanure-compost-wise.
The Cons: The urine smell problem has not been entirely solved. It will still show up, and it makes us slightly paranoid about how much liquid goes into the toilet, which makes us hesitate about having large numbers of guests over, which we enjoy doing. The fan makes a continuous hum, which isn't really noticeable with the bathroom door closed, but can be heard throughout the house when it's open. What's worse, is when the fan occasionally gets off-kilter somehow, making a "rrrooooowww-rrroooooowww" sound which drives Christy absolutely crazy. I don't mind it as much, but it definitely isn't ideal.
The Pros: Well first of all, the county approved our Sun-Mar, because it was on a narrow list of acceptable composting toilets, which is no small deal. Using the toilet is a comfortable, sanitary experience, and doesn't make our friends as uncomfortable as the five-gallon-bucket certainly did. When things are going well, there's no smell at all. The resulting compost looks very healthy and promising, and everyday we're reminded of the precious nutrients that we're saving for use in something closer to a closed-cycle ecosystem. The emptying is even accompanied by the earthy aroma of mushrooms. And of course, there's the amount of water we're not using.