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brownhouse lid
Tuesday, November 3 2009
Today was another day of progress on the brownhouse project. Early in the day I completed work on a PVC funnel to collect urine from the piss gutter and direct it out a cross-linked polyethylene pipe. This system could work like my household urinal plumbing system, where two PVC funnels empty urine into a bucket full of cellulosic waste near the northeast corner of the house. But the amount of urine generated by the brownhouse won't be large, and it might just be easiest to just dump it into a modest drywell.
Toilet seats have spacers between their two hinged components that keep them from sealing together. That's fine for a conventional flush toilet, but for a composting toilet, you want to keep the space between the shit pile and the place people venture to shit separated, at least until the point at which a connection between the two spaces is obviously necessary (so that shit can fall from one into the other). So in the afternoon today, I built a lid to completely cover and seal away the conventional toilet seat I planned to use in the brownhouse. Last night I'd built the wooden frame for this lid (it was made of wood I'd custom-milled on my bandsaw and had mitred corners). Today I cut a piece of Cor Ten steel to form a top surface for the lid. Being a rusting steel, Cor Ten isn't the most natural surface material for a bathroom. But this surface won't normally be in contact with anything disgusting. Its job is to seal the seat away from the cabin when someone isn't in the brownhouse. In actual practice, the lid didn't end up producing an air-tight seal. But it closed off air pathways to force air currents wishing to leave the decomposition chamber up the ventilation stack.
By this evening, there was enough infrastructure in place for me to use the brownhouse for its intended purpose for the very first time. It generally worked, but I found myself wishing there was fan to force air up the vent stack whenever the lid is raised. Otherwise, well, things don't end up smelling very pleasant. There's a big difference between shitting in a bucket in the big outdoors and trying the same stunt in a sealed space having only 60 cubic feet of air.
This evening I constructed an array of perforated pipes to use as an air supply for the the shit pile that will be forming in the trashcan in the brownhouse basement. Such an air supply is important for replenishing air in the pile that is being lost up the vent stack. The array of pipes allows the air to enter into the lowest layers of the pile and keep decomposition ærobic.
The array consisted of a vertical supply pipe made of 1.25 inch PVC. From this, starting about two inches up from the bottom, I added 90 degree fittings allowing for three 14 to 15 by 1.25 inch branch pipes. I drilled dozens of tiny holes into the branch pipes from the bottom side (so they wouldn't quickly get clogged). The reason I didn't have any branch pipes at the absolute bottom of the pile is that I expect several quarts of nasty dark brown fluid to accumulate there, and any pipes would quickly be submerged and rendered useless.
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