Running numbers of sawdust composting toilet capacities

We got to experience 6 days without water this last week. Well stopped working Saturday morning and I got the system back online last night. It was a great eye-opening experience and we're glad to have been able to see a serious gap in our resiliency in a low stress situation where it wasn't the end of the world sort of thing. Anyway, we realized just how much water we use every day when I was carrying upwards of like 50 gallons into the house just to wash dishes/hands and flush toilets. We did a deep dive on composting toilets and decided right away to get a system setup. We live in the middle of no where with no government code, zoning, etc. whatsoever, and lots of land. We treat our homestead sort of like a giant sandbox/experiment and this was right up our alley.

I might ramble a bit here, I'm thinking through this process and wanted to get it 1) down and 2) in front of others.

I plan on getting the toilet built and setup tomorrow. I was reading the Humanure book and in a side panel it mentioned that for every 100lbs of humanity 0.4 cubic feet (or 3 gallons) of waste is produced every week (including the sawdust). All total we're probably somewhere between 350 and 400 lbs for the five of us, so that's approximately 12 gallons of waste per week on the top end, or 2.4 5-gallon buckets per week of waste generated. I figure that a 4x4x4 compost bin (constructed from pallets) would hold a little less 64 cubic feet of waste, let's call it 60 cubic feet to account for "padding/sponge" material on all six sides.

Every week we would generate approximately 1.6 cubic feet of waste (0.4 cubic feet * 4). It would then take approximately 37 weeks (60 cubic feet / 1.6 cubic feet per week) to create enough waste to fill a 4x4x4 compost bin. That bin would then need to cure for somewhere between 9 months and 2 years. I am very interested in putting in a minimal amount of input and minimizing routine chores. To me the optimum setup is to keep the waste in buckets until there is an entire bin's worth of waste -- but having 88 buckets is a bit impractical, so I'm setting myself up with 12 to start with -- or a month's worth of waste. Every month I'd dump approximately 6.4 cubic feet of waste into the bin and at the end of 9 months I'd have a bin which is ready to be set aside to cook for another 9 months to 2 years (currently unsure how long I'm comfortable letting it go, we don't currently have a food forest or much perennials at all, so I'd prefer to err on the side of caution and go longer).

That means a two bin system would be adequate if we are harvesting this compost on a 9 month schedule. However, a 9 month schedule means a few things:

1. Non-cyclical rotation, ie the end of a bin's cooking time rotates and isn't a fixed date
2. Need to ensure the compost stays hot
3. Winter will inevitably screw up the compost

I don't think I can eliminate #1 without giving bins uneven rotations -- or creating bigger bins. If the bin is custom built instead of just being prefabbed pallets we could make it a little bigger and create bins that can hold an entire year's worth of waste. Slightly over 5x4x4 would be enough to achieve this for my family. That would mean that we are able to dump a year's waste into one bin and then that bin could then cook for an entire year's time, resulting in a single date every year for harvesting one bin and shutting down another to cook off. Then it's merely a matter of having 1 bin more than the length of time you'd like to cook the compost for. If you cook it for one year you need two bins. If you cook it for two years, you need three bins, etc. Of course this isn't going to be static for families since families grow and shrink over time as kids are born, grow, and then leave.

I think what I will ultimately do, however, is go with the flow and use pallets aka 4x4x4 bins and each will sit for an approximate time no less than a year, but possibly more depending on season and convience. As luck would have it, a four bin pallet-based compost bin setup is a super easy setup. You build it in a 2x2 configuration and this results in a very stable construction. Four bins is enough to hold almost three full years of waste which gives plenty of time to be lazy and would even let bins go for as long as two full years of cooking before a harvest, which is nice if a bin is unable to achieve a hot temp, the bin is created in the winter, or there is a suspicion of severe disease in the bin.

Thoughts?

Why not try one of these
Home bio gas producer
They are available in North America

Also if you want self selfciency, try Rainfall collection and use.
Its not as complicated or dangerous as those who dont understand will argue, my signature has a topic on the subject

There is a model that allows toilet waste to go directly into the system.

In my experience, most produce more waste than that. So you may need to make a 6 bin system.

I have one friend that has twenty something buckets so he builds the bin in one shot. I have another that has only one extra bucket to swap in while he dumps and cleans the first. Not sure which way I would do if given the choice.

John C Daley wrote:Also if you want self selfciency, try Rainfall collection and use.
Its not as complicated or dangerous as those who dont understand will argue, my signature has a topic on the subject

Collecting rain water is on the todo, but would require we get gutters/fix gutters, so that's not as immediately doable as slapping some 2x4s and plywood together. I also own 5 acres of pond which has an average depth of ~6 feet, ~1 mile of creek, and more springs than I can count, so harvesting water is something we are already doing in a more passive sense. I am more surprised at how much water I pollute and then pump into a tank underground than anything. I want to get a grey water system going, but 1) also not as quick as building a poop-box and 2) we need to wean ourselves off the septic before I can really start on that since a healthy and properly run septic requires a high volume of water, but a grey water system often undoes this.

Do you have 1/2 flush cistern and also a new rule ' men must wee outside"
A brick , a bottle of water sitting inside the cistern reduces the volume flush.
In Australia its encourage to leave urine unflushed it saves a lot of water.
Long showers are a problem also.
I dont think there is any problems with septics, just manage the water volumes involved.

For a family of 4 we found that a bucket was lasting about two days. You could fill them more, but we found it easier and more convenient to empty when they were a little less full and heavy. No smell, no mess. We don't use them now, but I would happily do it again. We have a mobile toilet setup for camping trips, and as an extra outdoor loo for when we have large gatherings.

You can also do well with an outdoor urinal. We made a "box" with some spoilt hay bales and filled it with sawdust. Aim in the sawdust.

Following what John said, I put urine soiled toilet paper in the garbage so that I don't have to flush that down so often.

When our water is out or limited (we have storage tanks), I would fill a 5 gallon bucket with rainwater harvested water to flush the few times a day it is necessary. Helps a lot.

I am looking to add some sawdust bucket systems for campers and RV people who don't want to fill up their blackwater tanks so much. I would very much prefer to keep urine separate otherwise it seems like you would produce a much larger volume of waste. Urine is easy to deal with, fecal matter less so, at least in my way of thinking. Although that would be more challenging with small children.

Update, I got the composting toilet setup last week and we've been using it since. The design will need to be reworked but I'm happy with what I made with a 2x4 and a third of a sheet of plywood. Now I'm thinking about the compost design a bit more. I'm leaning towards pallets since they're cheap/free, last 5 years or so, and are simple to put up. My wife suggested cinderblocks, but to get a 4x4x4 compost bin from cinderblocks is going to cost a bit of money and I'd like to avoid that. There's little waste/salvage material where we live so that's not something we could find for free.

I did have the thought of an IBC tote (300 gallon plastic tubs on pallet). That might be an ideal solution since it'd contain the humanure very  nicely with no spillage, could be moved very easily if needed with a 3pt carry-all, and would keep rodents/pests out a lot better. I would probably need to inoculate this with worms since they won't be able to tunnel up, but that's trivial. They're a little more expensive than pallets, but last indefinitely and are 1/4 the cost of the cinderblocks.