Minimum size of humanure bin

Hi

We're planning to build a compost toilet for a holiday yurt we're adding to our smallholding. We'd like a wheelie bin type solution where once it's full we can seal the lid and leave it compost down, rather than have a compost pile that we empty into. We'd also be using urine separation.

However, we'd prefer a low profile toilet enclosure without steps up so wondered if it was possible to use something lower than a wheelie bin such as a 80L or 110L UK dustbin? I know we could dig in the wheelie into the ground to get it lower but am interested to know if it's possible with a smaller bin.

Basically my question is does anyone know what would be the minimum size of bin/barrel that we'd need to be able to successfully turn humanure into compost? Note, we're in the UK (Scotland) so a fairly mild climate, and we wouldn't mind leaving the bins for a longer period to compost.

Thanks
Paul

this   is the first place to go if you haven't seen it


The compost process requires heat, air, moisture. When the pile is large enough it generates it's own heat and retains it's moisture longer, but should be turned periodically to keep the process aerobic, and watered occasionally if it's losing moisture.
Again, compost is a specific biological treatment by microscopic organisms, anaerobic organisms are thought to be the bad guys in the soil, compost organisms are aerobic and generally the good guys.

Nutrient ratio for compost is about 25 parts carbon to one part nitrogen- human waste is about at a perfect ratio,but urine is high nitrogen, and can accelerate the pile working. Inside I keep my bucket as dry as possible, but save the urine and mix it in later outside--this helps compensate for the sawdust which is almost pure carbon.

I always mix mine with other compostables  when I build a pile and usually try and spike it with a little extra nitrogen--chicken s**t--  so I save up my stuff until I get together a cubic yard/meter  which is the recommended amount for a good hot pile and then build the pile and turn it every couple days .

You can do this round or square, but too small or  spreading it out too thin won't generate the heat needed. Keeping it anaerobic inside a plastic bin  is how methane is generated, but it will need some added heat, and a way to collect the methane, and the end product still needs to be composted to finish the treatment.

I believe most places where composting is legally possible there is a two year minimum treatment period which might be your best option if you want to throw a bit at a time into a small bin, close it up and leave it for two years. That means depending on the amount generated you will likely want at least three bins, one being filled, one ageing, and one being emptied, but depending on how many people are feeding into this you could need a lot more--2 years can be a long time.

The actual compost period with a hot pile can be reduced to two or three weeks if you build the pile from scratch and turn it every couple days.  (1cubic yard)  

The bigger piles where fresh  buckets are emptied every day into the center  are acting like a furnace on the interior with straw on the outside holding in the heat and odor , and the process of opening the center for fresh additions allows oxygen to enter the pile - most human pathogens can't take  120 degrees temperature  for a few hours, so the actual treatment time can be dramatically reduced in a compost pile running at 135(F), a cold pile however and some of those organisms can hang on for a couple years.

If this is a B&B type situation, you really need to pay attention to the possible spread of pathogens brought in by outsiders.  So even if I was going the two year route, I would especially want to put it through a hot pile before scattering it around.

Bob,  the wheelie bin allows composting to occur in the same container that the deposit was made in.
It has a good track record, is protected from scavengers and it minimizes handling.

I have not seen a system that uses smaller containers, but given the very long composting time wheelie bin system uses,  they might work.
Adding worms to each bin should help.
Vermicomposting flushing toilets show huge reductions in bulk and pathogens.

I agree, sealing it up in the original containers, being plastic bins, might not be ideal for a few reasons.

When I tried using an open topped sawdust bin for nighttime urine, after a couple of weeks it went anaerobic in the bottom and gave off a powerful methane smell. If your materials are wet and anaerobic, they'll do that. Anaerobic decomposition doesn't do much of what you want from composting. It doesn't remove pathogens, it smells more like shit than fresh shit does, and supposedly it's not as good as compost for the soil.

If the materials are too dry, such as no urine at all, and faeces covered with bone dry sawdust, the faeces might desiccate (dry up) rather than compost, and that doesn't destroy the pathogens, give you nice compost, or make it much nicer to empty after two years.

Maybe if you cover faeces with damp sawdust that is already starting to break down, maybe it'll compost in there. But you'll want to make sure there's no water pooling in the bottom.

I have a composting toilet that kind of does what you want, but it is a pair of composting chambers, each about 3.3 (1 m) feet wide, and as tall as the ground floor of the house. The user accesses it from upstairs. We use one chamber for a year or two with dry sawdust as the cover material after each use, and then switch over to the other chamber, leaving the first to compost for a year or two before emptying it. We've been doing this system at the school I work at, for almost 20 years. Some years at the school, the pile had got too high before we closed it and emptied its partner chamber, so I think the bottom got too compressed and went anaerobic. In those cases, when we emptied it after a year sitting unused, there was a powerful methane smell. That only happened in about 1 in 10 of the chambers though, and I think it only happened when the pile was too high, like 5 feet or more. In my private house I don't think it will ever get too high like that. The chamber doors are not airtight, which seems helpful, and maybe a drainage from the bottom of the chamber would prevent it ever happening.

The "wheelie bin" system is not something I'm directly familiar with, but it sounds like an airtight plastic garbage can (when the lid is put on) this will break down over time, but even with the lid off unless there are holes in the sides it will be primarily anaerobic.

Elaine Ingham's work identifies anaerobes as problematic for soils, so before using an anaerobic "compost" worms or aerobic composting would be the best way to finally use whatever comes out of the wheelie bin.

With worms, I agree they are magical and they will eat the stuff and change what it looks and smells like, and at this point in time I would love to set up a bath tub sized worm bin and use them instead of hot composting, but do they take care of all pathogens? They probably do e coli pretty good, but that is just the tip of the iceberg and e coli don't last that long in a healthy soil anyway.

If you know of other data that shows worms can destroy disease and parasites in human waste the way a hot compost method does, please publish the link.

Humanure may not be trademarked at this point in time, but Joe Jenkins certainly has published the most comprehensive work on it, and his system has good science and great references, so when I see that word I automatically think hot compost/Joe Jenkins.

All the other methods I've seen using worms or in the ground composting rely on the 2+year rule-  I'm going to guess the wheelie bin wants that amount of time also.

I will admit that composting the way I described is a bit tedious, and for one person I didn't have enough even after a year to make a full pile, so I would import other manures and grass,leaves, etc to build a hot pile, which took even more time, but at the end of the two weeks or so in the spring I had lots of beautiful compost for my gardens and I knew it was safe to use and alive with healthy soil organisms.

Thanks all for the info & advice.

I'm planning something like this system (only possibly with a smaller bin) https://permaculturenews.org/2018/12/21/how-to-make-a-compost-toilet/  . So the bin will drain away moisture through a grill near the base, and be ventilated top, base and with perforated pipes on the inside so the process will be aerobic, though obviously not as much air as a compost heap. The only difference is we want to separate the urine off as with it being for holiday guests keeping smell to a minimum is important, but I guess will still need to add some moisture to prevent everything getting too dry.

Maybe the best way to go is to trial with smaller 80/110L bins and if we find they're not composting down sufficiently on their own we do as Bob suggests and transfer the contents to a larger compost heap to finish the process off.

Oh, thanks for the link, I see what you are thinking about. Which isn't that much different from just putting a five gallon bucket with a smaller box and toilet seat and dumping it outside more often.

Let us know how that works out for you.

bob day wrote: If you know of other data that shows worms can destroy disease and parasites in human waste the way a hot compost method does, please publish the link.

https://www.nps.gov/articles/denali-mountain-compost.htm

https://www.tandfonline.com/doi/abs/10.1080/1065657X.2001.10702015

jacque greenleaf wrote:Warning, large copy pasta.


From the current issue of Worm Farming Secrets
(subscribe here http://www.wormfarmingsecrets.com/ )


"Can worms spread harmful bacteria such as ecoli and salmonella?"
~ Shauna Babcock

Hi Shauna,

That is a really good question!

Worms themselves are not hosts for pathogens, but the materials
they live in and consume CAN contain various disease-causing
organisms. Thus caution is certainly warranted when using
materials such as manure and sewage sludge, which can both
contain high levels of pathogens.

Not only are worms not pathogen-infested organisms, but there is
actually a growing body of evidence to suggest that worms
(specifically composting worms) can actually significantly reduce
populations of pathogens in waste materials.

Eastman et al. (2001) tested the effectiveness of vermicomposting
for pathogen destruction in biosolids (sewage sludge from waste
treatment plant). The researchers "heavily" inoculated two
biosolids windrows with four different pathogens - fecal
coliforms, Salmonella, enteric viruses and helminth ova. Red
worms (Eisenia fetida) were then added to one of the rows at a
ratio 1:1.5 (worm wt:biosolids wt) and left to process the
materials. After 144 hours the row with the worms was found to
contain significantly fewer pathogens than the control row. The
results strongly suggest that vermicomposting could be used to
achieve EPA Class A standards for biosolids.

In a 2006 BioCycle article, Craig and Ankers report on a
promising 'real world' example of a large-scale vermicomposting
system being used successfully to achieve Class A biosolids. A
Pennsylvania wastewater plant has become the first in the U.S. to
be granted a permit to make use of biosolids that have been
processed by worms. The plant utilizes a large-scale
(semi-continuous) flow-through reactor designed by Vermitech
systems (of Australia) to process biosolids 'filter cakes' - a
material that was previously landfilled. According to the
article, the resultant vermi-processed material has been well
received by local vineyards, golf courses and sod producers.

There is some evidence to indicate that worms can reduce
pathogens in manures as well (although this doesn't appear to
have been studied as extensively). Murry and Hinckley (1992)
studied the fate of Salmonella in horse manure processed by
Eisenia fetida. They observed an 8% reduction in the presence of
worms, and only a 2% reduction in treatments without worms. The
horse manure was completely sterilized prior to use in the
experiment, and the ratio of worms to waste was lower than in the
Eastman study - potentially explaining why reductions were not as
dramatic in this study.

Despite the evidence suggesting potential pathogen destruction
during the vermicomposting process it is still best to use
caution when dealing with materials such as manures and sewage.
Part of the problem is that even if the passage through the
earthworms' gut IS destroying these organisms, how can we be sure
that all the material has in fact passed through a worm? Even in
the most efficient systems there will undoubtedly still be at
least some unprocessed materials.

As an extra precautionary measure when using manures/sewage as
worm food, I'd recommend hot composting the materials for at
least a few days prior to feeding it to your worms. This has the
added bonus of speeding up the process and destroying weed seeds
as well.

REFERENCES

Craig, L. and S. Ankers. 2006. Vermiculture produces EQ Class A
biosolids at wastewater plant. BioCycle 47(2): 42.

Eastman, B.R., Kane, P.N., Edwards, C.A., Trutek, L., Gunadi, B.,
Sterner, A.L. and J.R. Mobley. 2001. The effectiveness of
vermiculture in human pathogen reduction for USEPA biosolids
stabilization. Compost Science & Utilization 9: 38-49.

Murray, A.C. Jr and L.S. Hinckley. 2006. Vermiculture Produces EQ
Class A Biosolids at Wastewater Plant. BioCycle 47(2): p.42.

Paul Barnes wrote:....
Basically my question is does anyone know what would be the minimum size of bin/barrel that we'd need to be able to successfully turn humanure into compost? Note, we're in the UK (Scotland) so a fairly mild climate, and we wouldn't mind leaving the bins for a longer period to compost.
...

one piece of information I didn't see in a quick perusal of this thread is (cubic space per person per quantity of time)

I found by keeping track of my manure creation over a 9 month period while doing composting is that I produced:
1 cubic foot/human/month.  

This is on a reduced diet, not a SuperSizeMe USA diet.

Another unit for a minimum volume for composting to take place is about:
1 square meter or a 3'x3'x3' square.


Good luck!

Thanks for those studies, it's good to see some work is being done

Despite the evidence suggesting potential pathogen destruction
during the vermicomposting process it is still best to use
caution when dealing with materials such as manures and sewage.
Part of the problem is that even if the passage through the
earthworms' gut IS destroying these organisms, how can we be sure
that all the material has in fact passed through a worm? Even in
the most efficient systems there will undoubtedly still be at
least some unprocessed materials.

I'm guessing you noticed the Denali project was limited to e coli and choliforms

and both the other projects used or recommended additional sterilization methods  either before or after the worms did their thing, the quote above from the long pasta pretty much sums it up.

It's important though not to get too caught up in Fecaphobia, and I will admit that even with hot composting the system is always open to some human error.  The small pile ( 1cu yard)method with turns, requires every bit of the pile get it's turn in the inner heat, and even the large piles Joe uses need care in the beginning, although as that pile grows it is easier to make sure the new stuff is totally engulfed right away.

Like I said earlier, I like worms, they are magic, I have an active worm bin in the corner of my room, but they get food scraps--and outside they invade  the compost when it is cool.

But if worms are the only method then the two year rule still applies,, and like the wheely bin project recommends, that product goes to shrubs and trees not garden food plants.

It would be good to see a study comparing hot compost vs worms with pathogen destruction  

Even though I'm advocating here for hot compost I would rather use worm bins  if they were  as well researched.

Been a while since I read the Humanure Handbook but if I recall correctly a covered 4-bay system should take care of any pathogen concerns.  Each bay consisted of a year's input and after four years the human pathogens would have run their course so time made up for any not-hot-enough-to-cook issues.  Time helps with the minimum batch size concern as well.  I have wondered why not make a shake-and-bake system if one had human pathogen concerns but those are just idle thoughts for another day. A single family system, known health status of the contributors, is different from a "public use" system of course.  I will be working on my own system soon on new land and plan on the sawdust/bucket system.  Humanure waste will be composted separately but the compost worm idea has created an interest.  

I actually don't remember anything about a 4 bay system or 4 years, from the humanure handbook, that would certainly work ok with vermicomposting, and two years is the generally accepted time for stuff to naturally decontaminate itself without any special attention.  i will recommend that wherever you put the piles, make sure they are isolated from the rest of the environment so heavy rains or stray animals don't scatter the stuff  prematurely.

I haven't read the 4th edition, but two years is the recommended composting time.  I've got a 1 year old pile that composted very nicely.  I'll be turning it in a couple of weeks and may add some worms to it once the weather warms up.

I have a very similar question to that of the original poster. What would you get if you stored a 5 gallon bucket of humanure, mixed with potting soil mix, or sawdust, for 4 years with the lid on but a hole or holes drilled high in the side for air?  What if this 5 gallon bucket also had a compostable bag inside to contain the 'product'?  Storage would be dry and at ambient temperatures in a very cool coastal climate.

I'm dreaming up a system for a wilderness vacation home on a dock over a saltwater beach at the base of a cliff.  Its hard to get up to actual land, so everything needs to be contained on the dock.  The owners are considering commercial composting toilet units but want to minimize power and water usage, problems, maintenance, mixing and mooshing, etc, and don't want to empty and clean 'live' buckets.  Finished material will need to be transported some distance also.  

My thought is to build a pretty box in the bathroom with a vent through the roof with inline fan for assistance, and put the 5 gallon bucket inside this box. The toilet seat will need some kind of gaskets to create an air seal.  You flip on the fan before you open the toilet lid to do your business.  There is  a compostable liner in the bucket.  Before the bucket is used you make sure you drill an airhole or several (for its eventual long storage and decomposition period).  Once its full enough, you tie up the bag and put the lid on and carry it to "THE VAULT."  "The vault" is a shed built tight with respect to air sealing, with an air in-flow vent down low and a very tall black abs 'chimney' pipe going out the roof- this is to keep any smells far away.  The buckets sit in this vault for 4 years, then are emptied somewhere high and dry in the woods and used again.  The large number of buckets required makes this an expensive system compared to most bucket systems, but comparable to commercial remote composting units.  The advantage is you never get close to 'live product'  (except when you are producing it), and you maybe never have to clean a bucket.  Also, you only empty and shuffle buckets once every year or so after an initial 4 year period building up 'product'.  Since this chore is done in batches spaced out in time, its easy to hire out.  

But after 4 years of waiting do you end up with something ok to dump in a pile in the woods, or sell to your neighbors, or do you just end up with dessicated poo poo stuck to the sides of the bucket that stinks when you rehydrate it trying to clean the bucket but is caked on so hard you can't really clean it off?  Assuming this could work, I'm thinking potting soil would be the best cover medium, but am I wrong on this?  Thanks in advance for your responses!!

For a small wheelie bin sized hot composter take inspiration from the 'HOTBIN conposter.  I made one out of an insulated wheelie bin. To save turning use aerated static pile. The XY-WFT1 temperature sensor from AliExpress is cheaper than the cheapest long probe compost thermometer and allows you to monitor hot composting remotely. It will also cycle a small aquarium pump for aeration. This will create the same furnace conditions as the center of a humanure pile but in an insulated environmental capsule. https://m.facebook.com/story.php?story_fbid=10209025690754872&id=1695551128

For a low profile you could use an old fridge freezer on its side as an insulated box  and compost one chamber while filling the other.

Paul Barnes wrote:what would be the minimum size of bin/barrel that we'd need to be able to successfully turn humanure into compost?

Paul, hot composting (kill) method is only one approach that has proven effective.  David Omick's barrel toilet is a cold composting method that was verified to be effective.  His approach uses less than a 55gallon drum, and since it doesn't get hot (perhaps a little warm in my experience with it), as long as you can keep it on average above 50F for the required 4month curing time and keep it aerated I don't think there is a lower limit to the volume.  Notice that he does mention on his urine diversion page that you need to "maintain sufficient moisture for effective decomposition".

As far as worms, the following technical paper provides a nice summary of many prior technical papers on the subject: Singh, Rajneesh & Samal, Kundan & Dash, Rajesh & Bhunia, Puspendu. (2019). Vermifiltration as a sustainable natural treatment technology for the treatment and reuse of wastewater: A review. Journal of Environmental Management. 247. 140-151. 10.1016/j.jenvman.2019.06.075.  I would add though that it might be wise to stick with a proven design for using worms with toilet waste, such as that shown in the cross section image on the Wiki Vermifilter page, taken from one of the technical papers.

Anna Edey's worm composting toilet design, documented in her Green Light at the End of the Tunnel book was also verified, and forms the basis of the design promoted at vermicompostingtoilets.net.  vermifilter.com provides another DIY design developed by a wastewater professional that takes advantage of some of the latest research in the field such as this more recent paper: Lourenço, Nelson & Nunes, Luis. (2017). Optimization of a vermifiltration process for treating urban wastewater. Ecological Engineering. 100. 138-146. 10.1016/j.ecoleng.2016.11.074.

Hi @Paul Barnes, I'm considering doing something similar to what you had planned here. I'd love to hear an update on what you ended up going with and how it went for you.