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Festival scale humanure composting

 
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I am part of organising a week long co-created festival in Sweden, with around 2500 participants.

This year we bought land and so have tried taking care of the toilets ourselves instead of outside contractors.

Unfortunately, the method used this year turned out to be not the best. Basically it was using urine separating toilets, and 20L buckets for the poop. The idea was that bokashi/some kind of mycelium is added to the sealed buckets, and left to grow for 2 months. After two months the buckets are opened and worms are added, and after 1-2 years they should have processed everything to be usable on trees.

The main problem was the urine separators, it turns out, 2500 not so sober people have a hard time aiming, so it was a big problem for the cleaning team. Separating the urine also complicates the design of the toilets, as they either need to be taller than the IBC tanks that the urine goes into, or the pee has to get pumped into the tanks from ground level. We tried the pumps and it really didn’t work. Having small 20L buckets was also lot of work as they fill up super quickly, and it’s expensive buying 500 solid 20L buckets.

Now a bunch of us are interested in trying a different solution for next year. I have been reading the Humanure Handbook, and its amazing! I haven’t found many examples of Joe’s system being used on a large scale though, SOIL in Haiti is the only one, and it seems it becomes quite a bit more complicated when its no longer just a small scale backyard endeavour.

I have found some videos on Joe’s YouTube channel of festivals in California using his method, however our municipality requires us to contain the seepage, which complicates things, we can’t just have big pallet boxes on bare ground.

Right now I’m thinking to place toilets directly on top of 1000L black IBC tanks, with a thick layer of straw and wood chips at the bottom. At the end of the week we would add extra straw on top, then let the tanks compost for a year until just before the next event. Then hopefully the contents will have gotten hot enough that they can be emptied to windrows on the fields - luckily we have a lot of land. There it could stand for another year or two and we could use the tanks again.

Excess liquid can be drained via the IBC tap and added back to the pile to evaporate, which is pretty much what SOIL does in their large scale operation. I get the feeling that we would want to add wood chips/bulky material to the cover sawdust used in the toilets, to introduce some more air pockets to the compost, and encourage people to use a lot.

Has anyone tried something like this? Would it generate enough heat to kill pathogens? It’s not exactly like Joe’s method, where cover material surrounds the compost on all sides, insulating it. With this technique we will only be able to add straw on the top, through an extra hatch cut into the IBC. Something I have considered is insulating the tanks from the outside, though not totally sure that would work.

Would enough oxygen be able to get into the tank, or would we need to add a lot of vents? I have found videos of people with concrete block compost bins, where air can only get into the pile from the top, and it seems to work well for them. Perhaps some holes in the sides and a powered vent drawing air out the top of the tank?

Even if we don’t achieve the required temperatures, could we just leave the tanks to stand for two years? Our primary aim is getting rid of the poop ecologically, if we get usable compost that’s just a bonus.


 
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Lots of different ideas around Permies.  

Have you read up on willow feeders?  
https://permies.com/t/161838/willow-feeder#1274768

You could be first to get this certification:
https://permies.com/wiki/156829/pep-greywater-willow-feeders/Willow-Feeder-Fair-Event-Public

I'm sure others will have input as well.

I'm really glad you're going this route.  Pleast share your progress and outcome!  The world needs more good examples of scaleable, ecologically sensible waste management.
 
pollinator
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Ironic that your buckets are sitting in a building designed for managing cow poop and urine...

A biodigester could be another option
solarcities has information about building one.
 
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Hi Xavier
I read read your post.   What a load of cr^p!   About 1,000-1,500 gallons by my estimation.    I wanted to offer some thinking to an already suggested idea.   First my credentials:  as a boy growing up on a farm I became interested in biogas production after reading Mother Earth News Handbook of Homemade Power.   I built a digester and operated it to the amazement of visitors until one day I blew myself up.   Such is the life of a young inquisitive pioneer.   I have also been involved in fecal production for many years.   It seems your current approach has some issues:
1) Handling.    The waste requires much handling due to the 20l containers.    I would like to meet the brave folks who volunteered for this task.    Perhaps not shake their hands but at least have a beer with them and get to know true heroes.  
2) System Complexity.      Separating the waste streams caused problems.    What to do with all those buckets?    If it were my town, just put each one in an Amazon box on the porch.    It would be gone the next day!
3) Time.    The aerobic process takes 1,2 years.   Time for another festival, time for more buckets!
4) Cost.    Lots of buckets and lids and a place to store them long term.

Although I am not aware of an example of this being done,  perhaps this might better be accomplished with anaerobic bio digestion.  
1). Handling.   I suggest going straight into 55gallon drums (pardon my English units).    Would reduce the handling by ~90%.   Some styles have a completely open top and can be sealed with a clampy device lid prior to moving.
2) Complexity.    Biogas production works best with the right ratio of nitrogen and carbon.    Both streams go together.    Perhaps the barrel is pre-seeded with the right amount of used coffee grounds or some other convenient carbon source or perhaps it could be introduced after each use.  
3) Time.    Anaerobic digestion occurs much more quickly under the proper conditions.    Probably complete within two months.  
4) Cost.  Probably 1 55g drum costs less than 10 20l buckets

What would this look like?   All the drums would need to be placed in a building where temperature could be somewhat controlled.  If the temperature drops, no problem, process just slows down.    All the drums are tied together with a gas line coming off the top.     It goes to another set of drums, one upside down in water to prevent mixing of air and methane.   Methane is a more powerful greenhouse gas than carbon dioxide so it is immediately burned off and used to heat the building to maintain optimal temperature.  I would expect with the aerobic systems you have described that methane is still being produced and released.     When the gas stops bubbling, anaerobic digestion is complete and all pathogens have been neutralized.   Next step would be to spread the effluent on a farmland.    Would be an excellent project to work in collaboration with a university so every aspect could be measured and documented.  
 
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Beau Davidson wrote:Lots of different ideas around Permies.  

Have you read up on willow feeders?  
https://permies.com/t/161838/willow-feeder#1274768

You could be first to get this certification:
https://permies.com/wiki/156829/pep-greywater-willow-feeders/Willow-Feeder-Fair-Event-Public

I'm sure others will have input as well.

I'm really glad you're going this route.  Pleast share your progress and outcome!  The world needs more good examples of scaleable, ecologically sensible waste management.



We briefly looked into willow feeders, however some people were concerned that all the land will eventually be entirely covered in willow trees! we expect to expand to 5000 people in a few years - where we were before corona. I think it still sounds like worth a try though, and a way to dispose of the poop if we don't get desired pathogen killing temperatures.
 
xavier be
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Kenneth Elwell wrote:Ironic that your buckets are sitting in a building designed for managing cow poop and urine...

A biodigester could be another option
solarcities has information about building one.



Yeah biogas does seem like a really good long term solution. We have around 28.000 euro budget each year for the toilets, so will need a solution that can work for a few years before we can afford something like that though.
 
xavier be
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Doug Sass wrote:Hi Xavier
I read read your post.   What a load of cr^p!   About 1,000-1,500 gallons by my estimation.    I wanted to offer some thinking to an already suggested idea.   First my credentials:  as a boy growing up on a farm I became interested in biogas production after reading Mother Earth News Handbook of Homemade Power.   I built a digester and operated it to the amazement of visitors until one day I blew myself up.   Such is the life of a young inquisitive pioneer.   I have also been involved in fecal production for many years.   It seems your current approach has some issues:
1) Handling.    The waste requires much handling due to the 20l containers.    I would like to meet the brave folks who volunteered for this task.    Perhaps not shake their hands but at least have a beer with them and get to know true heroes.  
2) System Complexity.      Separating the waste streams caused problems.    What to do with all those buckets?    If it were my town, just put each one in an Amazon box on the porch.    It would be gone the next day!
3) Time.    The aerobic process takes 1,2 years.   Time for another festival, time for more buckets!
4) Cost.    Lots of buckets and lids and a place to store them long term.

Although I am not aware of an example of this being done,  perhaps this might better be accomplished with anaerobic bio digestion.  
1). Handling.   I suggest going straight into 55gallon drums (pardon my English units).    Would reduce the handling by ~90%.   Some styles have a completely open top and can be sealed with a clampy device lid prior to moving.
2) Complexity.    Biogas production works best with the right ratio of nitrogen and carbon.    Both streams go together.    Perhaps the barrel is pre-seeded with the right amount of used coffee grounds or some other convenient carbon source or perhaps it could be introduced after each use.  
3) Time.    Anaerobic digestion occurs much more quickly under the proper conditions.    Probably complete within two months.  
4) Cost.  Probably 1 55g drum costs less than 10 20l buckets

What would this look like?   All the drums would need to be placed in a building where temperature could be somewhat controlled.  If the temperature drops, no problem, process just slows down.    All the drums are tied together with a gas line coming off the top.     It goes to another set of drums, one upside down in water to prevent mixing of air and methane.   Methane is a more powerful greenhouse gas than carbon dioxide so it is immediately burned off and used to heat the building to maintain optimal temperature.  I would expect with the aerobic systems you have described that methane is still being produced and released.     When the gas stops bubbling, anaerobic digestion is complete and all pathogens have been neutralized.   Next step would be to spread the effluent on a farmland.    Would be an excellent project to work in collaboration with a university so every aspect could be measured and documented.  



You have summarised the problems well. There is one big benefit in the 20L buckets in that they are easy for one person to move, but yeah it creates a lot of work and expense. 55 gallon drums full of poop and pee are going to be really heavy and hard to handle, hence aiming for 1000L IBC's and just using a forklift. Ideally we need a solution in which all the containers can be emptied before the next year, so we don't need 3x the amount of containers.

I am intrigued by the solution you have proposed, is it different from the digester you built yourself?
- Most things that I have read about anaerobic methods is that they take a lot longer than aerobic, but you say its the other way around?
- We will anyway add sawdust to keep the smell down during the festival, so I guess this would be enough carbon?
- What kind of temperatures would the building need to be kept at? the barn we have now is slightly insulated.
- Could you link to some info about how this method kills pathogens?

Thanks!
 
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I've used composting toilet for multi-day camps of up to 50 in the woods. Probably about 250 person-poop-days, total. Based on the Humanure Handbook system of sawdust, buckets, and keeping urine and poop together. People inexperienced with sawdust definitely do make a mess, and are hesitant about using it at first. From a user perspective, it it is important that each user does a "flush" with a scoop of sawdust to leave it clean and welcoming for the next person. Loose sawdust spills on the floor and looks messy.

For something like a festival I would go for a floor with wooden slats so loose sawdust drops through and doesn't build up.

If using buckets you need someone dedicated to swapping them out and keeping the area clean.

When you are done you don't really want things composting anaerobically in sealed buckets. Ideally you want a really hot aerobic compost heap. This is very situation dependent, but you could haul buckets off site and have a heap elsewhere. For the scale you are looking at I would probably construct a long "wall of haybales, so you can empty buckets over the wall without risking any splashback etc...

Getting it out of containers as soon as possible and into a compost heap does seem to make the whole process less stinky and unpleasant. And if being used correctly, with plenty of sawdust, no stage of the process should be stinky anyway. Nasty stink only happens with insufficient sawdust, not using it to cover between each user, or if it get sealed airtight and has time to go anaerobic. Sawdust is amazing at absorbing odour, and getting a really hot and sterile heap up to temperature fast.
 
Doug Sass
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Hi Xavier
I could not find a definitive article on Mitigation of pathogens through anaerobic digestion just many articles suggesting this is the case.    The ideal temperature for digestion occurs about 90-95 F.    Digestion also occurs at temperatures  120-150ish with a different type of microbes and this range i understand is more effective in reducing pathogens.    You need about a 30/1 carbon to Nitrogen ratio for optimum results so sawdust would be beneficial.     Also i did not mention that this process works better as a slurry (probably about 1/1) so more handling is required to add water.     I agree with Michael that your bucket system and even more so your tote system will quickly go anaerobic unless transferred to some other containment.    The batch system i described above is very similar to what I built years ago except I used a tractor tire inner tube to capture the gas.  
I think the promise of fast aerobic decomposition is rarely realized due to not being able to achieve aerobic conditions throughout.    Compost piles must be turned.  
Another issue I see with this festival waste stream even after successful remediation, it will contain trash and cups and more than a few cell phones so where do you put it to not pollute the environment?    You may still be faced with having it processed through a municipality.
I would like to know more about the system used at the festival Michael mentioned.    
This is great problem begging for a great solution.  
 
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Hi Xavier:

I'm Jeinny and we manufacture WCEco compost toilets, we rent them for masive events, we have a collection service in 5 major cities in Mexico, and process everything.
The largest event we have handle was an Ecobazar with ~6000 visitors during 2 days, but it's not the onlu one. Before that we serviced a Bycicle race with 2400 participants. And we are just getting ready for an event of 45,000 next month.

We never use diverting systems in public events, as they always lead to problems because people do not know what to do with the sawdust and tend to screw it. We use 20L buckets and have personnel there to change them and to be sure everything is going right. It's important and conveniento to use enough sawdust. Not only helps to have a 30:1 carbon:nitrogen ratio, but also, not diverting adds adequate humidity to the compost process.

After the event we process everything in composters 2x2 m composters. But recently we worked with a major university here in México to test the pathogen charge of the final product after a year in the composter and after processing it as bokashi and found that not all pathogens are gone, so know we are being extra cautious and we are working in making some changes to the compost process. So, I'm pretty sure the volume in a bucket is not enough to reach adequate temperatures to kill pathgens. I would recomend to process externally in composters larger dthan 1 m3.

You can see some images of our cabins for events here:
https://www.facebook.com/media/set/?set=a.1571973673228019

And some images of our composters here
https://www.facebook.com/media/set/?set=a.1571991936559526

 
xavier be
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Thanks Michael,

I've used composting toilet for multi-day camps of up to 50 in the woods. Probably about 250 person-poop-days, total. Based on the Humanure Handbook system of sawdust, buckets, and keeping urine and poop together. People inexperienced with sawdust definitely do make a mess, and are hesitant about using it at first. From a user perspective, it it is important that each user does a "flush" with a scoop of sawdust to leave it clean and welcoming for the next person. Loose sawdust spills on the floor and looks messy.

For something like a festival I would go for a floor with wooden slats so loose sawdust drops through and doesn't build up.

If using buckets you need someone dedicated to swapping them out and keeping the area clean.

When you are done you don't really want things composting anaerobically in sealed buckets. Ideally you want a really hot aerobic compost heap. This is very situation dependent, but you could haul buckets off site and have a heap elsewhere. For the scale you are looking at I would probably construct a long "wall of haybales, so you can empty buckets over the wall without risking any splashback etc...

Getting it out of containers as soon as possible and into a compost heap does seem to make the whole process less stinky and unpleasant. And if being used correctly, with plenty of sawdust, no stage of the process should be stinky anyway. Nasty stink only happens with insufficient sawdust, not using it to cover between each user, or if it get sealed airtight and has time to go anaerobic. Sawdust is amazing at absorbing odour, and getting a really hot and sterile heap up to temperature fast.



This is exactly the system I would have liked to use; a big haybale fort, theres a video on Joe's channel about a big festival using it here: https://youtu.be/a_DQyO2CPV0?t=335 Were not too worried about cleaning up sawdust, it was cleaning poop out of the urine separators that was the problem.

However our municipality requires composting have a sealed bottom so leachate doesn't get into the environment. This complicates things, we could either build a concrete containment system like this: https://www.youtube.com/watch?v=8lkBAiakmno&t=1569s or, a similar setup using IBC's to do the final composting in which will be a bit cheaper:

If we could skip the step of taking the 20L buckets to the final composting, and figure out a way to have the toilets directly on the IBCs that would be great. I guess as Doug says it will be tricky to ensure enough oxygen is getting im. I have been thinking something like this could work, its basically the same structure in the end as one of Joe's piles:


Its insulated on the sides and top, all liquid are drained, and it should be filled within one week. Air will be able to enter through vents cut into the IBC. Im really hopeful about this system and will test one at a 300 person event in October, will definitely report back here with the temperature results.
 
xavier be
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Hi Xavier
I could not find a definitive article on Mitigation of pathogens through anaerobic digestion just many articles suggesting this is the case.    The ideal temperature for digestion occurs about 90-95 F.    Digestion also occurs at temperatures  120-150ish with a different type of microbes and this range i understand is more effective in reducing pathogens.    You need about a 30/1 carbon to Nitrogen ratio for optimum results so sawdust would be beneficial.     Also i did not mention that this process works better as a slurry (probably about 1/1) so more handling is required to add water.     I agree with Michael that your bucket system and even more so your tote system will quickly go anaerobic unless transferred to some other containment.    The batch system i described above is very similar to what I built years ago except I used a tractor tire inner tube to capture the gas.  
I think the promise of fast aerobic decomposition is rarely realized due to not being able to achieve aerobic conditions throughout.    Compost piles must be turned.  
Another issue I see with this festival waste stream even after successful remediation, it will contain trash and cups and more than a few cell phones so where do you put it to not pollute the environment?    You may still be faced with having it processed through a municipality.
I would like to know more about the system used at the festival Michael mentioned.    
This is great problem begging for a great solution.  



90-95F should be possible if as you propose, the methane could be used to heat the building. We have also considered using a heating jacket like this: https://www.drum-heater.eu/product/heating-jacket-200lt-90-h800 which should be able to get the material up to 65C/150F to sterilise everything. If the result is a slurry, I think we will need to get that approved with the municipality first, their guidelines only allow composting so far.

I'm curious about your statement that the piles must be turned—there is a whole chapter in the Humanure Handbook called "compost myths" outlining why this is not true and actually bad for the process, he has been making working piles since the 80s without turning. There's also plenty of videos of people using his system and not turning their piles: https://youtu.be/_4oHdfFufOM?list=PLdpeKk29EPYTrw2ZvWxdPNVroH8XCPIUl&t=252

We're lucky that our event has a big focus on leave no trace, so there is generally not much trash in the toilets, people carry their own cups etc. We will use the final resulting compost ourselves, so I imagine it's easier to pick out any trash at the end of the process when it is less like poop and more like soil. I could see how this would be trickier if we are using anaerobic slurry though.
 
xavier be
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Hi Xavier:

I'm Jeinny and we manufacture WCEco compost toilets, we rent them for masive events, we have a collection service in 5 major cities in Mexico, and process everything.
The largest event we have handle was an Ecobazar with ~6000 visitors during 2 days, but it's not the onlu one. Before that we serviced a Bycicle race with 2400 participants. And we are just getting ready for an event of 45,000 next month.

We never use diverting systems in public events, as they always lead to problems because people do not know what to do with the sawdust and tend to screw it. We use 20L buckets and have personnel there to change them and to be sure everything is going right. It's important and conveniento to use enough sawdust. Not only helps to have a 30:1 carbon:nitrogen ratio, but also, not diverting adds adequate humidity to the compost process.

After the event we process everything in composters 2x2 m composters. But recently we worked with a major university here in México to test the pathogen charge of the final product after a year in the composter and after processing it as bokashi and found that not all pathogens are gone, so know we are being extra cautious and we are working in making some changes to the compost process. So, I'm pretty sure the volume in a bucket is not enough to reach adequate temperatures to kill pathgens. I would recomend to process externally in composters larger dthan 1 m3.

You can see some images of our cabins for events here:
https://www.facebook.com/media/set/?set=a.1571973673228019

And some images of our composters here
https://www.facebook.com/media/set/?set=a.1571991936559526



Hey Jeinny, awesome you're doing this on such a large scale! Thats exactly the conclusions we had this year after trying separators. Im a bit unclear as to what you meant with the lab results—was it both your compost piles and a separate bokashi method (in buckets?) that were not successful in removing pathogens? Did you monitor the temps in the compost? We will definitely have at least 1m3 compost containers. I guess your climate is quite warm there?
 
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Xavier, I think the IBC tote is an interesting idea.  I've managed composting toilets for a 3-day event with over 75 people.  We opted to use 55 gallon drums using the Omick Barrel Design but without urine diversion to reduce maintenance all around.  We received lots of positive comments and no negatives.  The barrels were hard to move though.  In my experience people prefer the depth of a 55gallon drum over the 5gallon bucket.  IBC totes would allow you to move them with a tractor, provide a comfortable space between user and the growing pile, and control leachate.

In the Jenkins method (which I currently use) the deep cover layer on the bottom and sides, along with digging a depression in the middle for fresh deposits helps keep the pile sufficiently aerobic.  Early on I wasn't doing a good job digging the center depression and noticed actinobacteria building up, indicating it was starting to go anaerobic in the middle, but it never went fully anaerobic.  On the flip side, I've learned to put cardboard around the sides of the piles because I've seen winter winds kill a pile in a matter of hours without it.  Based on my experience I'd worry that an IBC tote would not give you the air you want to stay aerobic, but having said that, high enough temperature over time will still kill pathogens even if it goes anaerobic and stinks.

If the pallet doesn't crack the raised edges of the base ridges and sides of an IBC tote under load, you could consider crossing the your proposed design with a Johnson-Su type passive aeration system (all compost is within a foot of an air tube).  You'd want to cap the air tubes during use/fill, and align them so they don't sit directly under the toilet seat.  You could also surround each IBC tote with something like a Tree Bog, with a front gate to allow removal by tractor.  In the storage location you could insulatie the outsides with strawbales.

For this method to effectively hot compost, you'd want to fill each bin rather fast (1, maybe 2 days) because it'll start to heat quickly.  You may also want to have a way of having the maintenance crew spread the contents within the bin being filled, perhaps using access hatches like ceiling tile boards for the "bathroom" floor.  As an alternative, if you have access to electricity you could consider setting up an active aeration system inside the IBC totes similar to the O2Compost Micro-Bin, which would allow you to fill the bin over the full week.
 
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xavier be wrote:was it both your compost piles and a separate bokashi method (in buckets?) that were not successful in removing pathogens?


We do not process them in buckets. They stay in buckets just until we send them to the process area (about 3 weeks after collecting them).  We have serveral composters (2x3m and 2x2m). We have some of the composters' results out off the norm, specially helmints eggs, and also in the bokashi but in lower qtty. Those were preliminar results and we will be analysing them with the investigators and will be conducting some more test and preparing processing variants to fully understand whats going on.

Did you monitor the temps in the compost?


Yes, we monitor temp an pH 3 times a day on each composter. Mexican norms requires that temp is above 55°C for 72 hours. We acomplish that but we will do it everything again making sure all process is correctly handled and all the measurements are correctly taken.

I guess your climate is quite warm there?

We have a 14°C average with min. 3°C and maximun on 24°C

I have to add that we worked our composters according to Jenking's method and one of our guesses on this results is that maybe there is not enough aereation, but we will test that too.

For the quality of nutrients and level of humification, the results were ok.

 
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Burton Sparks wrote:Xavier, I think the IBC tote is an interesting idea.  I've managed composting toilets for a 3-day event with over 75 people.  We opted to use 55 gallon drums using the Omick Barrel Design but without urine diversion to reduce maintenance all around.  We received lots of positive comments and no negatives.  The barrels were hard to move though.  In my experience people prefer the depth of a 55gallon drum over the 5gallon bucket.  IBC totes would allow you to move them with a tractor, provide a comfortable space between user and the growing pile, and control leachate.

In the Jenkins method (which I currently use) the deep cover layer on the bottom and sides, along with digging a depression in the middle for fresh deposits helps keep the pile sufficiently aerobic.  Early on I wasn't doing a good job digging the center depression and noticed actinobacteria building up, indicating it was starting to go anaerobic in the middle, but it never went fully anaerobic.  On the flip side, I've learned to put cardboard around the sides of the piles because I've seen winter winds kill a pile in a matter of hours without it.  Based on my experience I'd worry that an IBC tote would not give you the air you want to stay aerobic, but having said that, high enough temperature over time will still kill pathogens even if it goes anaerobic and stinks.

If the pallet doesn't crack the raised edges of the base ridges and sides of an IBC tote under load, you could consider crossing the your proposed design with a Johnson-Su type passive aeration system (all compost is within a foot of an air tube).  You'd want to cap the air tubes during use/fill, and align them so they don't sit directly under the toilet seat.  You could also surround each IBC tote with something like a Tree Bog, with a front gate to allow removal by tractor.  In the storage location you could insulatie the outsides with strawbales.

For this method to effectively hot compost, you'd want to fill each bin rather fast (1, maybe 2 days) because it'll start to heat quickly.  You may also want to have a way of having the maintenance crew spread the contents within the bin being filled, perhaps using access hatches like ceiling tile boards for the "bathroom" floor.  As an alternative, if you have access to electricity you could consider setting up an active aeration system inside the IBC totes similar to the O2Compost Micro-Bin, which would allow you to fill the bin over the full week.



Super info, thanks.
- Do you need to have a leachate tap on your Omick system, as you're not diverting urine, or is the sawdust sufficient to hold all the moisture?
- It seems the vent pipes in that system do not extend down to the bottom of the barrel, do you need to manually aerate them? or do you empty them into a "Jenkins pile" immediately when they are full?
- If filling within 1-2 days is necessary, then I guess IBC's might be too big - it would take the whole week for us to fill each one. Then perhaps wheelie bins are the way to go, like this https://www.youtube.com/watch?v=rlml3Lmdv2o - basically like the Omick but easier to move.

We do have electricity, I wonder if an IBC system like this could work with powered ventilation - couldn't see the specifics of how the o2 system works:
 
Michael Cox
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Just an observation.

You are concerned about leachate, which in understandable.

My experience has been that this is highly dependent on exactly what type of sawdust you are using. There is a vast difference in ability of different sawdusts to absorb liquid, and hence their tendency to go anaerobic and leach liquids. There are also differences in use that can affect this. For example, using "too much" sawdust is never a problem. At worst the compost is a bit slow to get going. But using too little sawdust can result in wet anaerobic sludge. Err on the side of going overboard with the sawdust and you should avoid leachate altogther.

Our best has been sweet chestnut sawdust from a local fencing yard. They can give us cubic meter bags for free. Their dust is very fine and dusty. A bucket of this after a few days of normal use is odourless, and the moisture from urine is evenly spread through the dust. There are no wet an sloppy portions to splash when you transfer to a heap.

Next has been our own dust from running the chainsaw. Tends to be bigger pieces.  A bit less absorbent, but adequate.

The worst was bought in pine shavings. We urgently needed an extra loo when the indoor toilet was not working for a week. Bought a few bags. It was basically waterproof. A wet sludge was at the bottom of each bucket. It was a pain to use, nasty to clean up, and slower to compost afterwards.

 
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Xavier, I wasn't as knowledgeable about cover material back then so we were using material that was a bit coarse which resulted in a little liquid buildup in the bottom of the barrels.  It made it all the more important for us to stir the contents with the hand compost crank.  After months of aging we did combine them into a common bin, but the goal at that point was aging and not hot composting.  I'd be curious how well it'd work with better cover material.  In the Omick design since you use the hand crank to aerate the compost the vent pipes don't need to go into the pile.

You could try Jeff Lawton's wheelie bin design.  I'm a little nervous about sending the leachate straight out though.  Maybe if you added worms so it could act a little more like a vermifilter.  Joe Jenkins suggests using wheelie bins might work great for municipal emergencies in his Compost Toilet Handbook, but more for the sake of transport.  You might find the book interesting as it covers many applications of his system around the world.

As far as the Johnson-Su method, I'm not confident a wheelie bin would have enough of a core to create sufficient self-heating for full treatment, but who knows.  The O2Compost system is proprietary.  There is an overview of the system here.  Around 4:30 he shows an outside view of the system I was thinking you might be able to figure out how to adapt to an IBC tote.  Note the blower, knife gate, and spacing of the two pipes that go into the bin.  More lengthy intro videos can be found here and here from which you can glean more.

I tried the 02Compost system with cow manure mixed with straw from information I gleaned online and ended up way overestimating the blower horsepower needed.  I later reached out to the company about trying it with humanure from my family of 8.  The rate of humanure production was too low for their system though as they're hoping to fill a 4x4x4ft bin over no more than about 3weeks, but that shouldn't be an issue for your event.  If it sounds interesting I'd recommend you reach out to the company and at least have a free consultation with them to see if it would be a good fit.

I must add, you have impressive drafting skills!
 
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I have nothing to add regarding technical details, but suggest that perhaps you could reach out to Natural Event ( products webpage ) for ideas.  I know that before the pandemic they provided composting toilet services to at least two festivals I attended with good results.
 
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Just an observation.

You are concerned about leachate, which in understandable.

My experience has been that this is highly dependent on exactly what type of sawdust you are using. There is a vast difference in ability of different sawdusts to absorb liquid, and hence their tendency to go anaerobic and leach liquids. There are also differences in use that can affect this. For example, using "too much" sawdust is never a problem. At worst the compost is a bit slow to get going. But using too little sawdust can result in wet anaerobic sludge. Err on the side of going overboard with the sawdust and you should avoid leachate altogther.

Our best has been sweet chestnut sawdust from a local fencing yard. They can give us cubic meter bags for free. Their dust is very fine and dusty. A bucket of this after a few days of normal use is odourless, and the moisture from urine is evenly spread through the dust. There are no wet an sloppy portions to splash when you transfer to a heap.

Next has been our own dust from running the chainsaw. Tends to be bigger pieces.  A bit less absorbent, but adequate.

The worst was bought in pine shavings. We urgently needed an extra loo when the indoor toilet was not working for a week. Bought a few bags. It was basically waterproof. A wet sludge was at the bottom of each bucket. It was a pain to use, nasty to clean up, and slower to compost afterwards.



Thanks for this info, very valuable. Unfortunately I have just found out that there is a massive shortage of sawdust in Sweden—yes its crazy. This is because many people use pellet heaters in their homes, and the pellets are made from sawdust, combined with the general wood shortage. We have contacted a few sawmills but they only want to sell to municipalities or big companies.

We can buy wood shavings, but it sounds like thats not the way to go—they are probably pine. I have read online somewhere, about someone putting straw into a big bin, and using a weedwacker to cut it up into dust. We can get straw bales from the farmer on our land so going to give this a try.

The toilet system we had this year used biochar, not really as a cover material but just to absorb smells. Has anyone tried using it as the main cover material?
 
xavier be
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You could try Jeff Lawton's wheelie bin design.  I'm a little nervous about sending the leachate straight out though.  Maybe if you added worms so it could act a little more like a vermifilter.  Joe Jenkins suggests using wheelie bins might work great for municipal emergencies in his Compost Toilet Handbook, but more for the sake of transport.  You might find the book interesting as it covers many applications of his system around the world.



We wouldn't actually send the leachate out, but simply add it back to the bins so it can be absorbed again by the compost, and evaporate, as they do here: https://www.youtube.com/watch?v=8lkBAiakmno&t=1569s
As we'll be composting in IBC tanks, adding worms seems like a good idea as they cannot enter naturally from the ground—I guess after the main thermophilic phase is the time to add them.

Im going to need to read up more about vermifilters, and get onto the compost toilet handbook!

Watching that o2 video, it seems like the air should be pushed into the compost, not drawn out of it as in my previous drawing. I could definitely see that working with an insulated IBC.
 
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Morfydd St. Clair wrote:I have nothing to add regarding technical details, but suggest that perhaps you could reach out to Natural Event ( products webpage ) for ideas.  I know that before the pandemic they provided composting toilet services to at least two festivals I attended with good results.



Thanks, yeah I have a friend that just went to Waking Life in portugal that uses their toilets. Got some info about their toilet design but not their composting process, most companies want to sell their services or consulting, not really share information. Boom festival also doesn't want to share info about their system unfortunately.
 
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Heres an update:

We had a small event last weekend, around 50 people for 4 days. We built a prototype compost inside an IBC tank to see how it would go.

First the top of the IBC was cut off


These air pipes were connected to a plastic pallet, which also holds some textile to keep the straw onto the side of the tank


This construction was placed inside the IBC, and the sides and bottom were filled with straw


Finished construction


I estimate only 50-60% of the capacity remains after the insulation straw and drainage pallet is added


Here is the full tank after the event, we also added food scraps


Both an analogue and digital thermometer are used to record the temperature


We had one indoor toilet and one in the barn


We filled it with around 100L poop/pee/sawdust, 75L food scraps, drained and re-added around 80L leachate. There was definitely still room left.
After the event, the compost thermometer read 21C, outside temp was around 7-13C. The next day it went up to 30C - so its working already! We will get the digital thermometer results in a month or two.

I actually emailed Joe, he responded after we had already built it and said the air pipes are probably not necessary:
"The oxygen issue is way overblown. As long as the organic material is not under water, there will be oxygen in the mass. There is no need to add it. That's why compost can be made on concrete, in brick bins, plastic bins, etc., without needing to add any additional oxygen, pipes, air holes, or anything else. Unless the pile is too big. Then it can smother itself. Just don't make it too big. It's that simple. Too big means too high. A maximum height of a meter and a half seems to work well."
 
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Wow, looks like very promising initial results!  Keep updated, please!
 
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