Adding redworms to a desiccating toilet system
February 2nd, 2010
Update 2/7/2010: Just so you know, there are some graphic pictures below. If you aren’t interested in viewing humanure, please don’t read further.
Last week I had an interesting meeting with Mike, an official at a local state park. They have a desiccating toilet that just isn’t working as well as they had hoped. Here’s a picture of the toilet system from the outside.
Eldorado Canyon State Park Bathrooms
Below is a picture of the system from the inside. They have two large plastic vaults that have air flowing from the outside into them. The feces and toilet paper are held up via a metal trough, and air flow drys them out. Wood shavings are regularly spread in the system, which is supposed to help control odor (I think). Finally, the entire mass of poop is regularly sprayed with fresh water (on a timer). That is supposed to help decomposition. (I don’t understand how the water spraying and the air drying work together, and neither did Mike.)
Eldorado Canyon Desiccating Toilet System
Below is a picture of inside the system. Yup, that’s human feces and toilet paper. I visited during the winter, and the level was not high. Mike said that the entire mass freezes solid during the winter. The white horizontal line in the middle of the picture is a tool that lets someone distribute wood chips or move poop.
Inside Eldorado Canyon Toilet Vault
The primary issue with the toilet is a high pH leachate that accumulates at the bottom of the system, below the trough. Eventually that liquid gets so high that the system needs to be pumped. You can read his description of the issues; he goes into far more detail about what has been tried. He also summarizes what we discussed and the plan moving forward:
- I’ll build a compost bin, in the basement with the vaults, loaded with worms.
- I’ll get the worms started with food scraps from the office.
- I’ll make some experimental sections in the worm bin, and try adding some of the, er, material from the devap toilets, and maybe try soaking a different section with the excess water. The idea is to see what the worms like and thrive on.
- If the wigglers like human waste, but not the bilge water, then I’ll leave the vaults unmodified, add worms, and let ‘em go to town this summer.
- If the wigglers like human waste AND the bilge water, I’ll add worms to the vaults, and scale up by periodically pumping some of the waste water up into the stack.
- Worms will crawl and explore, but they also like dark and quiet. It’s highly unlikely that they’ll crawl up to the main floor.
- If the worms are successful, they’ll probably die off every winter in the cold vaults. The warm, freestanding compost pile will have to be maintained during the winters.
- It’ll be interesting to see what happens with the odor.
- I’m totally rooting for the worms. It would be phenomenally cool if worms could thrive on the wood chips, waste, and wastewater.
It will be interesting to see how the worms adapt to a diet of human waste. I found some links that indicate that they should do alright (thanks, Google Scholar!). Here’s one on a worm composting outhouse, which discusses some of the unique aspects of vermicomposting human waste (as opposed to the more typical feedstocks of yard and kitchen waste):
The worm bin should be operated like any worm bin. The moisture, temperature and aeration needs are the same. One difference is that human waste has a Carbon to Nitrogen ratio of 20:1 and so it needs a high carbon material added to decompose best.
Here’s another article discussing using vermicomposting to stabilize sewage sludge. Here’s an article about redworms reducing pathogens (a topic I reviewed last year). This is an interesting article on how feedstock affects E. Foetida weight and length (pdf). And here’s an interesting abstract for an article on the effects of stocking density and feeding rate on biosolid vermicomposting that is worth excerpting:
Specifically, the focus of this study was to investigate and establish an optimal stocking density and an optimal feeding rate for the vermicomposting of biosolids, with paper mulch provided as bedding. A stocking density of 1.60 kg-worms/m2 (0.33 lb-worms/ft2) and a feeding rate of 1.25 kg-feed/kg-worm/day resulted in the highest bioconversion of the substrate into earthworm biomass. The best vermicompost was obtained at the same stocking density and a feeding rate of 0.75 kg-feed/kg-worm/day.
Based on reviewing these articles, a key component of this system will be adding enough carbon to keep the worms happy. The main source of carbon currently is wood shavings, but they are purchased. I think that shredded paper and/or leaves would be good alternatives. Some calculations should be made to determine how much bedding substance to add.
In addition, redworms need a pH between 5 and 9, and I believe the leachate was well above that (update 2/7/2010: per a conversation with Mike, the pH of the leachate is 8.5 or 9). I don’t think the worms will be able to process or reduce that liquid directly. However, the source of the leachate seems at first blush to be the fresh water spraying, so if the worms process the waste and help maintain humidity, less spraying may be needed, and thus less leachate may be created. Even if the same amount of spraying is required, the worm castings may retain more of the water, and reduce leachate in that manner.
I’m a huge fan of Mike’s plan to start small (with a 55 gallon drum) and see how the redworms react to waste and/or leachate. This experimentation will be cheaper and easier to control, as well as giving Mike a chance to become familiar with worm keeping.
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11 Comments Add your own
1. tom vineski | February 8th, 2010 at 8:58 pm
Thanks for info and interesting dilemma. An old friend (Al White)from PA designs/operates composting toilet systems for residences and commercial park applications and may have some ideas on the maintenance of your system, in addition to trying out the redworms. http://www.best-composting-toilet.com/index.html
A quick look seems like the moisture may be running off and not getting thoroughly mixed to critical point to begin decomposition, especially with the ventilation. This is real problem in the west., air is needed for decomposition but too often just dries it out too much to decompose. Just a few thoughts
2. vermicomposting | February 18th, 2010 at 2:10 pm
Tom,
Thanks for your feedback. Do you have any suggesstions on how to ensure the moisture doesn’t run off? There really isn’t an easy way to mix things mechanically.
Also, I’ll make sure to pass on Al’s info.
3. vermicomposting | March 5th, 2010 at 11:03 pm
Here’s an update from the state park employee:
http://eldoprt.wordpress.com/2010/03/01/the-worms-have-landed/
4. Carolyn | March 24th, 2010 at 5:58 am
As you found out worms do not like pine shavings. Adding lime was scarry.
Also for a small system with special needs, like the worm system, it may be worth the extra money for the less white toilet paper, the recycled tan stuff. The white, just like white copy paper was probably bleached with dioxon which the woms may not like as much.
Also do not be surprised, or alarmed if instead of worms doing the task, you get volunteers especially suited to the job… BSFL. Black Soilder Fly Larve. They may be just what the job requires. When their job is done then the worms take over with the addition of maybe some corrigated cardboard.
You might want to get the worms to live for you with just kitchen waste and cardboard bedding to get familiar with them. Then add in the componet of human waste. But keep your main stock of worms safe from testing.
You might want to get the BSFL to live for you with just kitchen waste to get familiar with them. Then add in the component of human waste.
That way $$$ and time will not be spent on new stock as you experiment.
One of the big issues is the liquid waste and the solid waste together. Both need different treatment. Adding the two together makes what was difficut to treat more problematic.
This also seems seasonal. The whole process dependent on the life cycles of the changes of amounts of waste during the seasons and the life cycles of the BSFL and composting worms in the different temperatures.
This is way better than mixing waste with valuable potable water and dumping it in rivers.
Good Luck
5. Carolyn | March 24th, 2010 at 6:09 am
Also the liquid is going to immediately turn into ammonia which the worms will not like. I suggest the addition of biochar to absorb the ammonia. It will also give a nicer product of compost at the end. And it has tons of nooks and crannies for the wee beasties. The wee beasties actually eat the waste. Then the wormies eat the wee beasties.
Also pete moss is a non renewable resource and may also be too acidic for the worms. Is anybody shredding cardboard in the area?
6. Carolyn | March 24th, 2010 at 6:57 am
Oh, and what chemicals are being used to clean the toilets? Some of this probably gets into the system.
Also if the woms die in mass they will smell much worse than any smells before them.
7. vermicomposting | March 24th, 2010 at 9:12 am
Carolyn,
Thanks for your intelligent and useful comments. I will ping the state park employee and see what he has to say for this. I don’t think any chemicals are being used to clean the toilets–they’re just pit toilets–but I could be wrong.
As far as the ammonia, I believe the idea was to have enough carbon in the system that the nitrogen/urine would be absorbed and could be broken down by bacteria. If the pits are large enough, worms can migrate away from nasty substances, and toward enjoyable environments.
Dan
8. Mike | March 25th, 2010 at 8:01 am
Carolyn:
Thanks so much for the advice and questions.
* Most of my worms are living happily in their bin. It’s a mix of food waste, peat moss, shredded paper from the office. Apparently it’s better than pine shavings, because they’re hanging out in the mix, and the smell of the bin has changed from “decay” to “sweet” (I wish I could describe it better). The worms seem pretty peppy.
* No one is shredding cardboard near me – BUT – I have lots of cardboard from the office and a steady supply of community service from Boulder County. I can definitely make more than enough shredded cardboard to meet my needs.
* Peat moss: I’ll switch. The “soil” around the park is very mineral, and probably very inhospitable. The only things that grow well around here are pine trees. I’ll get a few yards of “planter’s mix” from one of the local landscaping companies.
* I did things bass-ackwards. The worms were happily frolicking in their food/peat/paper mix, so I loaded up one of the vaults with food waste and peat moss and added a handful of worms to the vault. We had a surprise cold snap – all the worms went deep into the pile and hid for a few days, but now they’re all back up top in the food/peat/poop mix. I figure if they like the humanure, they’ll eat it, if not, I’ll keep throwing food waste in the vault this year.
* Liquid separation: I think it will work out fine. The liquid percolates to the bottom of the vaults, and hopefully makes a pretty straight descent. The solids stay atop the pile and are shuffled around by yours truly. In the past, I was just spreading them around, now, I’m moving (some) of them into the worm zone.
* I’ll get some biochar. Should I introduce it in the top of the pile, or down amidst the leachate?
* Chemicals for toilet cleaning: I made the switch last year – the park is chlorine/lysol/etc. free. I use an extremely low concentration of a product that contains some soap and some critters that are very beneficial for septic systems. I also use a product that has some soap and some citric acid for cleaning the urinal on the men’s side – the citric acid is necessary to keep uric acid crystals from building up in the pipes. Like the human waste liquids, any cleaners fall directly beneath the toilet risers, and hopefully percolate fairly directly down.
* Thanks to Dan’s generous long-term (Sorry, Dan) loan of The Humanure Book”, I’ve gotten the idea that mixing food and humanure is a very good way to get a thermophyllic pile going. I’m hoping that the worms will enjoy the mixture, and if the temperature of the pile gets too hot, they’ll migrate to cooler sections of the vault and keep doing good work.
* I’m using the men’s vault as a control, and the women’s vault as the test bed. As of this morning, there is almost no water standing in the bottom of the women’s vault, and about one inch standing in the bottom of the men’s vault. Both have received the same amount of fresh-water spray. I doubt that the worms et cetera have already made that much of a difference, but it’s possible.
* I’m meeting with Ecocycle’s compost/worm guru next week. I’ll post on this thread if there are some meaningful developments.
9. Carolyn | March 25th, 2010 at 10:52 pm
“loaded up one of the vaults with food waste” may be why “one inch standing in the bottom of the men’s vault” Food waste has a high percentage of water. Maybe add absorbant material such as cardboard, egg tray, coffee take out tray, or coir. Now a days places like whole foods or museums serve their food and salad on brown paper plates that can be composted.
Worms do not do well with a lot of citrus. People will feak with the thought of adding citric acid to the bin. I think it is fine because it has a purpose, is probably the best and safest product for the job and percentage wize is small. I bet it works out.
Biochar. It would be good if the liquids could perculate through it. Like if a catchment area from the urinal could drain through some thus removing or retaining the stuff farmers pay money for to fertilize the soil.
Users are not adding covering material. If they were I would suggest about a coffee measure per use of biochar. Or mix into other covering material for people to add a cup full or so to cover each use.
“solids stay atop the pile and are shuffled around” We want to minimize the need to do that and have the worms do this. However everyone loves to check on the worms and bother them. So don’t be surprised if the bin maintainers still do it for fun just to “check on the worms.”
It would be great if the designer of the “desiccating toilet system” could be found to explain the “fresh-water spray”. Inquiring minds want to know.
10. Carolyn | March 25th, 2010 at 11:09 pm
Your work reminds me of posts I read a while back. I googled but only found reminents of his work. The person has not posted that I can see online in months. On the biopod.com he posted “I have been working on a vermiculture project for our city in my job at the wastewater facility over the last couple of months. Getting close to start pre-composting our sewage sludge in preperation to feeding a worm bin, probably by the end of next week. If anyone’s interested I have been keeping a log at http://www.arkiegold.com/Vermiculture.html.” The site is gone and even the way back machine does not show it. But I remember going to the site and seeing he had designed cement tanks to further dry material to then put in worms.
I remember bits if his website. He was a city worker who used his own time and even his own money to “conducting a pilot project with worms in our city sewage sludge and maybe the worms would be able to remove drug residue from the solids portion of the waste stream.”
There are lots more vermicomposters out there, well on line, who would love to hear about your project. Many have done lots of testing tempting the Gods that like to smell dead worms. The systems are getting way better. They know way more than me. I would love to see their posts here. The funny thing is. For every vermicomposting FACT there is an equal and opposite vermicomposting FACT. But we all have the same goal of MORE worms and Vermicastings. And we all love bothering our worms to see what it is they are doing.
11. Carolyn | March 25th, 2010 at 11:14 pm
http://forums.gardenweb.com/forums/load/verm/msg090924072871.html This too may be the same person at the very start of their work on the subject.
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