Pit Toilet - Methane Digester For My Campground/Farm/Park
This is adapted from the barrel in barrel digester systems seen on YouTube. These systems have a feed tube which adds kitchen waste to the system at a point below water level. Gas rises to the top of the system and cannot escape up the feed tube. These systems generally have a spot where water leaving the system is saved for use on plants. The effluent water from this system would need to be treated as contaminated and run into a weeping tile or other accepted system for human waste. This would include urine and some water to flush the pipe occasionally. Sawdust could still be dusted over waste but a certain amount of water and waste would always sit at the bottom so it would not always stop odour from rising up the tube.
The top of the feed tube could be capped with either a low flush toilet or the type of toilet common in campers that use only a small quantity of rinse water. This would deal with both odour and visual considerations.
PUT IT IN A GREENHOUSE I'm thinking of this as a means of dealing with large numbers of visitors in a park setting. A cold concrete septic system set into the ground breaks down waste quite slowly(55F subsoil temperature around here) compared to a system set within the warmth of a greenhouse. A big tank placed against the insulated north wall of a greenhouse would act as thermal mass for the greenhouse. Waste would be broken down more slowly in the winter, but the number of guests using the toilet would also drop drastically during cold weather. A Rocket Mass Heater and bench could be built against the exposed surface which would enable winter heating of the tank which would wear an insulating blanket.
IRRIGATE FORAGE PLANTS WITH EFFLUENT
Rather than dumping the effluent into a weeping system, I would prefer to use it on forage crops for animals. There is a perfect spot to grow forage which lies just south of and downhill from where I'd like to build the public washroom and greenhouse. This area could be broken up into a few little paddocks which could be watered and then allowed to sit for several days before the animals are allowed onto it. Most of our rain comes in winter followed by a spring and summer dry season which coincides with the tourist season and the growing season. This south facing gentle slope needs constant irrigation if it is to produce grass. The natural vegetation is mostly drought adapted trees and shrubbery.
I also plan on building a couple green roofs which will provide forage for goats and sheep. They are a great draw for touristy enterprises.(“mom, let's stop at the place with goats on the roof” ) These roofs are in full sun and could definitely use some irrigation during the driest 6 months of the year.
With the camper type toilet, it is possible to get about 8 flushes per gallon. Some visitors are bound to be idiots, so I'll figure on 5 flushes per gallon. A 1000 gallon irrigation storage tank could therefore store effluent from 5000 flushes produced during the 6 month rainy season. This works out to 27.5 flushes per day in the off season. I can't see averaging anywhere close to that number of uses during winter. If I ever do manage to create a business which attracts greater numbers of visitors it would be simple enough to scale up the system or build a separate one funded with the wheelbarrows of money that so many visitors would represent. ----------------------------------------------------------------------------------------
I see many people going to great lengths to produce 10 minutes worth of cooking gas per day(not that there is anything wrong with that.) For me the gas is a handy byproduct which will be used in a park related cooking area about 75 feet from the digester. The economics of this are simple for me. It is likely to cost between $7,000 and $10,000 to put in a conventional septic system to serve this many guests. So that's my starting point. I'm pretty good at sourcing supplies and would expect to spend less than this on a methane digester. Regular weeping systems require a large area of ground where tree growth must be prevented and you must be careful whenever planting or using equipment there. My place is currently worth about $35,000 per acre. When fully developed it should be worth $150,000 per acre. Restricting the use of some of the best flat area, effectively reduces the value of that spot. Much of the land is steep.