Composting Toilet

For the longest time, I wanted to put a composting toilet in the Mill Creek NetZero Home (MCNZH). My reasoning is that, at some point, I think we’re going to be forced to compost our waste for food production (*reader rolls eyes at raving hippie communist blogger*). Seriously, once the fossil fuel-based fertilizer is gone, how else will we keep our land fertile?

Joseph Jenkins’ book “The Humanure Handbook: A Guide to Composting Human Manure” is a must-read for people interested in long-term solutions to poo and pee. Composting them uses zero water and turns them into valuable products.

Once we started looking harder at composting toilets, though, we backed off. The reasons:

1. A composting toilet such at the Pheonix system needs to be vented continuously to the outside. The 5 Watt fan would consume about 44 kWh of electricity annually. More importantly, though, it would mechanically expel warm air 24/7 from our house during heating season. So our super airtight home would become leakier because of this toilet.
2. These toilets are prone to outbreaks of flies. No kidding. Now, I’m pretty earthy - a regular Green Frickin Giant of earthitude. But I draw the line at having flies crawling out of my toilet bowl.
3. The system would cost about $10,000 (if memory serves). That’s a lot of money for air-leaking flies.

BRAC (Grey Water)

So, we went with the next best thing - in the MCNZH, we’re going to flush our toilets with shower water.

Brac Systems is a Montreal-based company that sells tanks that collect washing machine and shower water (see picture above). In a new home like the MCNZH, you plumb the showers to drain into a big (300-450 litres) tank (there’s an overflow that drains into the regular sewer system for when the tank gets full). Then, you run cold water pipes from the tank to the toilets in the home.

The advantages of this system are:

1. During the heating season, the heat in the shower water won’t just escape into the city’s sewer system. Instead, it will sit in the BRAC tank and be released into the home. That’s a lot of heat (I’ll add the calculation later when I find my formula).
2. The 20%-30% of household water that go down the toilets will be “free” - we won’t be flushing with potable water, but with water that was previously considered a waste product.
3. We won’t be pulling in 6 degree Celcius water from the city during heating season. At 40-60 litres of water per day, with such an energy efficient house, the amount of cold water that we won’t need to heat up is significant (again, I’ll publish the exact saving later).

I’m really excited to stop wasting so much precious drinking water on the toilet. In the climate-changed, water-constrained future, we’ll all need to start being wiser with our water.

We’ll be purchasing our BRAC system from Trimline Design Centre (on 6772 - 99th street ). Oh yeah, the systems aren’t yet legal in Alberta. A minor detail - we’re looking at the big picture here! It’s only a matter of time before they become legal. Regardless, we’re putting one in.

(cross posted at www.greenEdmonton.ca )