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Q. We are wanting to build a small, environmentally friendly cottage, something for one person to live in. We’re currently researching composting toilets and getting quite confused by all the contradictory information. Suppliers of course claim how perfect their product is, while competitors and consumers give voice to contradictory claims. Do composting toilets actually work? Are they a viable option? What about cost effectiveness? Are they truly better than septic systems?

Cedar United Church
Cedar, BC

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A. Dearest Cedar United,

My readers seem to have potty topics on the brain lately — first this question about doggie doo, and now your query on the even less appealing topic of what to do with our own unmentionables. But as much as we’d all like to pretend this isn’t an issue, my favorite children’s book has it right: Everyone poops. Now what are we to do about it?

I sympathize with your confusion on the composting option. For all that waterless toilet manufacturers tout how eco-friendly, smell-free, and easy their products are, there’s still the unavoidable fact that they involve holding the household’s bathroom business in the house instead of whisking it away for someone else to deal with. But after reviewing the latest developments in loo technology, I’m happy to report that yes, composting toilets do work, and yes, one could be a viable option for your cottage.

As you may know, Cedar United, composting toilets work by breaking down waste into carbon dioxide and water through natural microbial action, reducing bulk by about 75 percent. What’s left — after a year or so of diligent composting, that is — is a nutrient-rich humus devoid of dangerous pathogens and other ickiness. There’s more going on here than simply bringing the outhouse inside (thank goodness).

In-home composting toilets come in a variety of shapes and sizes, but tend to follow two general designs. Larger, bi-level toilet systems connect the toilet to a composting bin in the basement; these units can handle greater, er, volume, have a longer retention time, and need to be emptied less frequently. Smaller, self-contained systems are cheaper and easier to set up, but the contents must be dealt with more often. Sometimes this involves burying the finished compost (check local regulations!), but more often requires a visit from a licensed septage hauler. Oh, and both types employ some sort of ventilation (accomplished with negative pressure and/or a fan) to pipe odors outside. I encourage you to consult with your builder and local authorities to decide which model is best for you.

For the toilet to function properly, your cottage dweller would need to maintain proper aerobic conditions through some combination of adding carbon-rich bulking material (such as sawdust) or compost enhancer, controlling moisture, and occasionally turning the toilet contents via mechanical handle or good old-fashioned pitchfork. Make no mistake: Pulling this off requires some degree of environmental commitment. Without it, you may run into problems.

Why bother? In a word: water. Composting toilets greatly reduce your home water use. Thirty percent or more of the average household’s water gets flushed straight down the conventional toilet — and then there’s the water and energy required to treat the effluent at your local sewage plant. Composting toilets are also zero- or low-electricity, as opposed to another flush alternative, the incinerator toilet. And while you’re counting composting’s benefits, don’t forget to count the buzz your bathroom choice is sure to create among houseguests.

You asked how composting toilets compare to septic systems, and here, too, water is the main advantage: After all, with septic, you’re still using treated, potable water to rinse away waste. Septic tanks also often use electricity-fueled pumps instead of simple gravity to move toilet contents through the system. And unmaintained septic systems carry the risk of contaminating groundwater (which may or may not come with the unwelcome addition of a sewage lake in the backyard).

There’s also the matter of maintenance. With a septic system, you’ll need to manage household water use, keep up the drainfield, and get your system professionally inspected and pumped regularly. While you may have to attend to a composting system a bit more frequently, the environmental benefits of using one can outweigh the extra work.

As to your question about cost: Well, it depends. Installing a septic system can run you from $3,000 to more than $35,000, depending on the type you choose. A composting toilet, on the other hand, can cost anywhere from about $900 for a self-contained, single-user model to upwards of $7,000 for bigger, more advanced thrones. (And this ultra-DIY option is a real cash-saver.) The composter is certainly cost-competitive — and you’ll be saving on your water bill to boot.

In short, Cedar United, a composting toilet could be just the ticket for your charming new cottage, provided the resident is up for the challenge, and for the increase in time spent thinking and talking about poop. Best of luck.

Microbially,
Umbra