Gord Baird and Ann Baird have written the definitive guide.
New Society Publishers produces a Sustainable building essentials series, edited by TreeHugger favourite Chris Magwood and Jen Feigin, who have “scoured the world of sustainable building to bring you the techniques and systems that deliver measurable benefits in terms of greater energy efficiency and reduced environmental impact.” They have been sending copies for years, but I never felt qualified to comment on rammed earth construction or rainwater harvesting, earth bag construction or natural plasters.
The first thing I have to say is that if you are even thinking about getting a composting toilet, you should read this book cover to cover before you start. I have owned Sun-mar and Envirolet continuous systems and after all this time, have learned that I have not been managing them properly. Because right in the introduction, the authors note that there is no such thing as a composting toilet.
Composting is a specific process, one that occurs under specific conditions – and those conditions do not exist in any toilet.
What the toilets do instead is collect the deposits, minimally process it so that it can be buried and thus reintroduced to the environment, “or better yet, it is further composted to a state that sanitizes and reduces pathogens to a level so safe it can be used as a beneficial nutrient resource.” Some of this happens in the toilet, and some of it after the stuff is removed and happens somewhere else. It all requires proper management and understanding of how it works and what is coming out of it. The stuff I have been taking out of my toilet is not quite ready for prime time.
I have long made the case that we should all be using composting toilets, and that the idea of using drinking water to flush our waste out into lakes was an accident of history and a really bad idea. It wastes a valuable resource of fertilizer and phosphorus, and requires a vast and expensive infrastructure of pipes and treatment plants. But there has always been resistance, with comments like "no one will want this inside their house. I know this, because I still have a few teeth in my head and a few friends in town."
The Bairds demonstrate that this need not be the case, that our waste can be properly managed. They point out that “compost toilets, due to their small scale, allow for a cost-effective and simple method of gathering and processing nutrient-dense resources, with the option of beneficial reuse.”
There is another benefit to compost toilets; when they are working properly, they actually make for nicer bathrooms than regular ones. The sweetest smelling public washroom I have ever been in was in the Bullitt Center in Seattle, because air is constantly being sucked down through the toilet bowl.
The downside of a compost toilet is that the stuff never goes away; it’s not flush-and-forget like conventional toilets. Some of the big ones like the Clivus Mutrum units do not need a lot of maintenance, but at some point they have to be cleaned out.
I have thought that compost toilets should be a service rather than a product, where it is installed in your home under contract, where the company comes and takes the waste away on a regular basis, perhaps through a hatch on the side of the house so that they don’t even come in. I have also admired the more complex systems with moving blades and vacuum pumps and all this complex technology to separate us from the poop and make it as simple and flush-toilet-like as possible.
In their conclusion, the Bairds go in the other direction. They look at the complexity of the natural processes and ask, “Why would we even try to mimic these systems using plastic and metal when nature has already perfected all of this in the soil?” They end up favouring the simplest and cheapest humanure or batch commode system, basically a bunch of buckets and sawdust.
Just as many people are thinking about going off-grid, we have to think more and more about going off-pipe. That’s one of the ambitions of the Living Building Challenge, and should be the ultimate goal in sustainable living, where we don’t ship our waste somewhere else but deal with it ourselves.
At the more practical level, I could have saved a lot of money over the years had I read this book first. It’s great bathroom reading.
See them all at New Society Publishers.