Cloacina Development Blog » aerobic batch composting

Portable Composting Toilets for Multi Day Events

molly — Fri, 04 Nov 2011 23:37:23 +0000

The Cloacina Project with design and implementation from PNCA’s graduate students in Collaborative Design created an open source hardware platform for toilets, urinals, hand sinks and privacy screens for portable low cost dry toilets. Recognizing that hardware is only half the problem the PNCA students addressed the user interface by creating a training protocol, help line using GroupMe and signage to assure the safe and hygienic conditions for the users.

The toilets: The toilets use one 55 gallon drum cut in to two pieces to act as the throne that shields the 15 gallon collection drum underneath the toilet seat and the cut off piece acts as a step up to the throne. Materials required include a 55 gallon plastic drum, a 15 gallon drum (fiber or plastic), nuts, bolts and metal brackets. The total cost were $43/toilet. This includes the price of buying hazardous material certified plastic liners because we chose fiber drums as our collection vessel. We paid $8 to 10 per 55 gallon drum. After a user uses the toilet they are encouraged to put a scoop or two of coffee hulls on top of their deposit. Our motto was ”if you can see it, we can smell it.”

The urinals: The urinal design was not as elegant as the toilet design though proved functional during the convergence. The urinal is a simple funnel mounted to a privacy screen made from a cut up 55 gallon drum and costs $47 per unit. For odor control their is a ping pong ball in the base of the funnel that allows urine to flow in but seals the pipe into the urine barrel when not in use (>see DIY urinal explanation).

The hand sink: The hand sink is a modification of a Finish design called the “andy handy” and cost less than $6 per unit.

The privacy screen was designed by Dave Laubenthal and Morgan O’hara and implemented with help from the across the Collaborative Design MFA program. Each structure was made from lashing bamboo with zipties. The structure included one stall for a urinal, two for Step Up toilets and one stall with a Sit Down toilet and a hand sink. A hand sink hung outside each station.

Basic Design Principles
Our goal was to design a private portable composting restroom that would:
collection method
-have no offensive odors
-commode can support users and provide solid connection to the floor
-connects commode directly to composting chamber
-prevents user contact with human wastes during normal operation and failure
-free of corrosive parts, rough or sharp edges, or other hazards which could cause injury to persons adjusting, servicing or using device.
-all access ports are sealed to prevent the infiltration of pests
-be acceptable to users

compost chamber
-prevents infiltration of rainwater and groundwater
-watertight
-provides adequate access for regular service and removal of humus

Compost Pile, Modified

Mathew — Mon, 21 Jun 2010 23:26:00 +0000

We eliminated the inner bin our our compost about eight weeks ago. The air gap between the thick wire and mesh bin channeled too much heat out. Now we have just a 4′ diameter mesh pile full of wood chips, with a 24″ column of vegetable compost in the middle, and temperatures pushing 60ºC in the center. Our system is to load the compost roughly every month, letting vegetable waste build up in 5-gallon buckets, and then loading 10-20 gallons into the pile at a time. We shovel off the outer 12″ of wood chips, put vegetables mixed with paper & cardboard into the center column, and then cover back up with wood chips.

New Composter Completed

molly — Wed, 31 Mar 2010 06:02:10 +0000

Check out the corresponding Instructable for this project.

Rodent Resistant Composter – More DIY How To Projects

So Mathew and I are back with a new and improved composter for our backyard, a plan we sketched out while recovering from a flu picked up in San Francisco. After the cable to the sensors got eaten by some fuzzy creature last week, I went out and bought 22′ by 4′ wide 1/4″ galvanized mesh to build a new and improved composter. Mathew suspected it was a bird, but a burrow hole confirmed it was a rat. If rats want to get at our delicious composter tonight, they’ll have to chew their way through metal, 13″ of wood chips followed by more metal. Take that rats! Raccoons don’t even try!

The whole set up looks like it might have landed in our yard by a distressed starship. We rigged it together from salvaged materials from around the house and our local salvaged building supply store for a total of $80 not including the soon to be installed temperature monitoring system. $60 was spent on the mesh, which definitely was a bit overpriced at our local hardware store.
How it works: The solar air collector warms air to roughly 20 degrees hotter than ambient. This pre-heated air is blown in to the bottom of the compost pile for 6 minutes each hour during hours of solar gain from 7 am to 7 pm. I built this from a pallet we had on hand, ducting and insulated it with a terribly unattractive wool skirt. We’ll be monitoring the temperature starting later this week to determine the optimum aeration schedule. For now this aeration schedule is based on research of the New Alchemists’ composting greenhouse which used 17.8 cubic feet of air per square foot of compost per day (Fulford 9). Our fan is a tiny little 12V 0.22 amp fan used for cooling computers which blows approximately 1 cubic foot per minute. The goal is to aerate our pile without cooling. Maintaining thermophilic temperature without manual stirring. The compost container is surrounded by 13″ of wood chips plus a wood chip cap on top for insulation and odor prevention (God forbid).

The bacteria present in a well insulated pile with enough oxygen will theoretically raise the temperature of the pile to a thermophilic bacteria friendly temperature range of 113 F to 150 F. The New Alchemists found in their study that composting horse manure generated 103 to 177 BTUs per cubic foot of compost (Marshall et al. 5). We’ll see if our alpaca manure and table scraps will generate as much heat.

I’m so glad this composter is up and running and I hope that now that we have a heated aeration system I will stop dreaming that I am a compost turner.

Fulford, Bruce. The Composting Greenhouse at New Alchemy Institute: A Report on Two Years of Operation and Monitoring. New Alchemy Institute. 1986.

Marshall et al. Improved Composting Greenhouse Designs Based on Energy, Nitrogen, and Materials Handling Research. New Alchemy Institute. 1987.

the bottom of the compost chamber: Mathew's attention to detail amazes me.