Better Humanure Carbon Stock

I recently read the Humanure Handbook which was great read with tons of good rationale on recirculating a vastly abundant resource. I however am a little nervous about using wood chips or shavings as a carbon stock as it is one of our most overharvested resources, and would be difficult to produce locally. Any ideas on a more sustainable stock to balance the high nitrogen ratio of humanure? soil would be a thought as it is widely available,and has the necessary microbiology to kickstart the composting process. It would however make the necessary temperatures to safely mitigate the potential biohazards of human fecal matter in the soil much more difficult to reach due to its high density. Any thoughts?

woodchips and sawdust are a byproduct of woodworkers and lumber industry...they will continue to be made whether or not you use them

Most "browns" will work. Leaves, straw, mature grass, etc. They don't absorb liquid as well so you need more of them if you don't separate 1 and 2. And that means a lot more emptying of buckets.

And you don't have to use just one thing, or the same thing all the time.

Wood shavings are just about ideal so if you have a source, use it. Better composted in your yard than burned or landfilled.

I regularly pick up big bags of used coffee grounds from the coffee shop, dry them, and use them as cover material for my bucket toilet. They're free, they're being produced anyway (and thrown in the dumpster if I don't pick them up!), and they make the toilet smell quite nice.

I never had much luck getting humanure compost to heat up no matter what I used in it, so I've always relied on time, deep burial, and long-term crop uses to hinder pathogens. I used local clay soil for years in my bucket system, partly because I was keeping the bucket in an apartment situation where it needed to be absolutely odorless, and I figured if clay works for cat litter, it should work for my own "litter" too! Since for most of those years I was always planting trees, the buckets would simply go directly into the planting holes, and gave good results there whereas a fluffier compost would have created drainage issues. A fluffy mulch material like wood chips can lead to odor problems.....a few things help: have them half-composted first, have them moist, and add some wood ashes....

Brendan Dunne wrote:I recently read the Humanure Handbook which was great read with tons of good rationale on recirculating a vastly abundant resource. I however am a little nervous about using wood chips or shavings as a carbon stock as it is one of our most overharvested resources, and would be difficult to produce locally. Any ideas on a more sustainable stock to balance the high nitrogen ratio of humanure? soil would be a thought as it is widely available,and has the necessary microbiology to kickstart the composting process. It would however make the necessary temperatures to safely mitigate the potential biohazards of human fecal matter in the soil much more difficult to reach due to its high density. Any thoughts?

We've lived with a "Humanure" bucket system for over 30 years. The bucket of poo is emptied into an outdoor compost bin and layered with grass, used sheep bedding, leaves or whatever and left to sit for a year before it's used to fertilize the corn patch. Lately we've been using recycled coarse sawdust. We get one of those large bags of it each year to pack roots after harvest for storage in the root cellar. As each bin is emptied, the sawdust is spread out to dry and put aside for the poo compost bin. It somehow seems less wasteful if the sawdust is used twice. We have a separate bucket for the urine which is used on our regular compost piles or occasionally directly into the garden during the growing season, depending on the crop's needs. We don't add any of the carbon into the bucket until it's emptied, other than toilet paper. Odor control is handled by a small fan which we turn on before opening the unit. The fan is connected into the plumbing vent. Conventional toilets smell bad to me in comparison.

I have been using Spagham Peat I buy by the bag at the hardware store or garden center. As long as you keep everything covered with a layer of dry material, there is no smell, except for the smell of the peat. I'd love to find another material that could save me some money, but this isn't bad.

I don't have a composting toilet (yet) but here in the Caribbean they use bagasse (sugar cane pulp) and rice husks as cover material. Sugar cane is a popular snack to chew on, and a family could definitely produce quite a bit of pulp if they like it enough, but I'm not sure that they could produce enough pulp to fulfill their bulking needs at 100%. I guess if they save all of their grain husks from the prior season (corn, millet, and sorghum included), that could help quite a bit.

I wonder if dried banana leaves would work too...

I guess the key is to look at what YOU produce in abundance. That's where you'll find your answer (which will be different from mine).

I visited an off grid farm that used tree leaves for carbon and then added the waste into a worm pile. The worms process the "offerings" faster than just composting and they eliminate many of the harmful bacteria that can grow and accompany humanure. It was a very lovely system that I would highly recommend.

Has anyone thought about or tried woodchips currently growing mushroom mycelium? Could a certain fungus be "taught" to consume pee? Poo? Paul Stamets seems to be able to teach mushrooms to eat things they normally wouldn't...
At the very least you could grow mushrooms in sawdust in buckets and then when the last mushroom has been harvested, you pee on it. Mycelium containing soil is supposed to hold more water, soooo what do you think?? I know pee is used easily, so it may not be needed for that, but maybe the spent mushroom stuff could be broken up and used for the poo?

I use rotted and chipped bramble (wild blackberry) stems. They grow abundantly and when used as cover are much lighter than wood chip. So far so good - been using them for a couple of years now.

In the process of making plasters for natural building - earthen plasters, lime plasters; doesn't matter - you need fiber for tensile strength in the base coats. Concretes use synthetic fibers, or metal bars, but there are many time-tested solutions to providing this fiber organically: manure, animal hair, straw, and other plant fibers. I liked to use chopped straw. There are several ways to produce it, including a leaf shredder, a reversible leaf blower/shredder, or a weed trimmer in a metal trash can. I used the last method, finding that its best to cover over the mouth of the can with a cloth and to chop sight unseen; otherwise the dust blows you out of the room.

Having bags of such chopped straw leftover, I plan to use them for my own bucket-style home composting toilet. The texture is a lot closer to sawdust than to raw straw, and I think it should work well. What's more, when chopping the straw for plastering, it is important to make the straw just right: not too fine, but not too course, either. You need the average piece to be no more than an inch or so in length. But this wouldn't matter if using the straw in a toilet, and in fact the finer the better, so the chopping could be a much more carefree endeavor.

This is all future tense, so I can't vouch for any results, only my theory. If it does work, however, then I'll know that I can easily and inexpensively produce an unlimited quantity of "brown" for my humanure composting in the event that my local supply of real sawdust should dry up or become too expensive. I can buy straw locally at no more than $3 or $4 per bale, and it doesn't take too long to chop once you get set up and going. So I'd bet that in one afternoon and for less than $20 I could pick up, chop, and bag enough straw to last me in the bathroom for many months.

Anyone else with experience using chopped straw?

We have been using a composting toilet for 7 years now and have found that something called 'stump dirt' works very well. It is the 'dirt' you find in decaying logs in the woods. It holds water well and composts the poo quite nicely. We grind it with a hand cranked compost shredder after drying it out on a tarp. We occasionally throw in some grass and the dust and detritous I get when I sweep. Since November we have been using a separate bucket to pee in and have been emptying it on one of our compost piles. That has made a big difference in the toilet, especially with manky odors.

Down south, sea grass is an overplanted ornamental. It has been an excellent carbon for me, but was only used in short-term camping situations. [It was abundant and light enough to backpack some sea grass mulch.] The blades are sharp enough to slice a tomato. Okay well, that's an exaggeration, but it does cut your hands up without gloves. Hmm, that's not taking care of the human, so nevermind it's not a good idea. Definitely thinking in the grass family for growing the pooper mulch, though. I'm pretty clueless about MT plants though. Do y'all have grass?

We started out reading Joe Jenkins (Humanure) and decided to try the waste paper idea.. he didn't have much use for the idea but we have that in abundance so figured it worth experimenting with since Jenkins hadn't gone into any detail on his experimenting results and difficulties........

Shredding junk mail was how we started... dusty business and too much hassle when crushing newspaper seemed more satisfactory for the chemistry...

This 'stuff' is not 'cover' (if you're eating right, there's no smell to stifle).. it's chemistry to mix nitrogen and carbon with a light amount of moisture and enough airflow

so the keys were the moisture integration (office paper doesn't integrate well) and a sense of 'gift-wrapping' layers (abundant coverage and easy shaping over the bucket's contents) and newsprint seemed satisfactory... we had considered the sawdust at one point when abandoning the shredding, located a solar kiln owner and started hauling and heaping it but sawdust just invited tons of bugs... ugh.......

and the woodworkers and sawmills were leery of individuals coming to pickup (insurance worries) and so they favored commercial takers with their big trucks... newsprint was far better and the local county has sunday deliveries from two presses..... free and abundant and just works well at the bucket end...

biobin doesn't get over 115*F (likely since the carbon content is higher than straw and sawdust and I don't stint the gift-wrapping) but that just means the disinfecting takes longer (looked up the charts on time vs temp) but we'd built an extra biobin anyway since we liked the conservative idea of a 2year cycle.. more usage for those trees than just recycling their newsprint after just that one use..... this is year 8..... pleased so far

Almost two years in, our present to Canada on Canada Day 2014, we have used different sources of sawdust and lately have been mixing our coffee grounds and tea leaves in as well. Any carbon based material, either ground or screened to the right consistency should work. I like sawdust because it is readily available and free but if I didn't have easy access to it I would substitute ground leaves and coffee. I have some leaf piles maturing that I would like to try this year, time permitting.

I've been viewing coffee grounds as mitrogen sources and not carbon sources in the garden. This surprises me that it works for humanure. Learn something new every day! : )

Here in Cinci, there's a group that maintains a database online of 'waste' from businesses and promotes the idea that the waste from one business is the resource for another business....

Good stuff is developing apparently because sawdust is not 'free' much any more... at least not without driving beyond the city region.....

Isn't this happening elsewhere??? I'd have thought it would be part of the move to green-up coal plants (like is being done in Ontario Hydro, as we used to call it) where the brush and landscape waste and such is ground and added to coal... I'd wonder just how much that trend will change availability of some 'carbon stocks' from business waste for free, like here........ ttyl

A couple of carbon sources could be Humates, charcoal, or Bio Char. These would help with controlling odor and if you use microbes they can start the decomposing process in the bucket.

From a volume standpoint Jenkins systems don't use a lot of cover material. A small woodworking shop would easily produce more material than one household would use and small producers should normally be agreeable to giving away material since they don't produce enough to sell unless they store on site for a period of time. Not worth the hassle to them.

Biochar would be a good choice for results but not for average use. Too messy.

Janet Branson wrote:I've been viewing coffee grounds as nitrogen sources and not carbon sources in the garden. This surprises me that it works for humanure...

I was thinking the same thing. Could anyone confirm, please...? Would coffee grounds serve as a suitable carbon in a humanure compost?

I do not know if this info is of any use or not BUT - used to live in Mozambique and many people used cess pits which had to be cleaned out every few years. Many could not afford to have this done and some magic pills were thrown in to dry it out. I was told that an alternative to these expensive pills were yeast tablets. These would start working quickly and dry everything out. Have never tried it but it may give some of you ideas.

Definitely thinking in the grass family for growing the pooper mulch, though.

Along those lines, would bamboo work as a carbon feedstock? It grows quickly and abundantly. I envision a stand growing next to the toilet.


As for the coffee grounds question,theoretically, coffee grounds usually have a C:N ratio of 20:1, nice to add to a slightly carbon dominated compost to get the "perfect" 25-30:1 ratio for composting situations, including vermicomposting, which goes fastest at 25:1. Human waste is around 8:1, so adding one gal of coffee grounds to one gal of human waste would result in a C:N ratio of 14:1. This is not terrible, and may not even be stinky (as discussed above), but if you added 1/4 gal of shredded paper (129:1), you would get 27:1, about perfect. The waste paper may actually be provided by the coffee filters.

To be clear the carbon material is not getting rid of the odour it is trapping it below a stink barrier. I tried to remember a proper term but I am a bit tired so stink barrier it is. This is why the particle size is important, too large and the stink permeates. It also means that the bio shield does not need to be thick, just complete.

Thank you, Wyatt.

I thought that the C:N ratio was important, because I drew a parallel between smelly compost and smelly you-know-what. Sometimes the feedstock for my red wigglers smells worse than human waste, and if the ratios are N-heavy, the smell hangs around even with a barrier; on the other hand, it disappears quickly when the ratios are good. I wonder if this parallel holds any water?

Wyatt Barnes wrote:To be clear the carbon material is not getting rid of the odour it is trapping it below a stink barrier. I tried to remember a proper term but I am a bit tired so stink barrier it is. This is why the particle size is important, too large and the stink permeates. It also means that the bio shield does not need to be thick, just complete.

Is it not also true that, by balancing the C:N ratio towards the optimal 30:1, adding carbon impacts the nature of the biological processes driving decomposition and reduces odors that way? In my experience, balanced composts don't stink, no matter their ingredients. Whereas nitrogen-rich composts become slimy and stinky, no matter how odorless the original ingredients were. My parents' grass clippings pile was a prime example: a sweet-smelling ingredient, unlike poo, but too nitrogen rich so that once the composting started it smelled awful. Incidentally, if you swing too far in the opposite direction and get a carbon-rich compost, they don't stink either, but they decompose more slowly and generate less heat than an optimally balanced mix.

OK, so I'm pretty new to composting, especially the humanure variety, so my question is this. How do you know what your C:N ration is? Is it by weight? Volume? How do you know if your ratio is correct? Do you use a scale? I can just picture my wife sitting down to 'do her business', then weighing the bucket, then adding peat at a 30 to 1 ratio....

Quick google search yields one ounce of poop for every 12 pounds of bodymass, so one pound of poop for a 160 pound person per day. Also, roughly 0.4 gallons of urine, or 3.3 lbs. This yields 4.3 lbs of human waste per person per day at the average 8:1 C:N ratio. There are guides for different feedstocks, as well as calculators, to be found online. I can't make recommendations based on feedstocks which will be particular to what you have available, but those resources can.

Michael from my point of view I don't care what any ratio is. I am using a cover material to absorb liquid and provide a barrier to odour not to create a perfect composting mixture. The compost is a byproduct produced over a long time and it is my opinion that everything balances out in the end, pun intended. If you are using the Jenkins method you cover adequately for odour not for any balance so no measuring or weighing is necessary. Our posted how to instructions say use about a cup of sawdust.

Michael Kalbow wrote:OK, so I'm pretty new to composting, especially the humanure variety, so my question is this. How do you know what your C:N ration is? Is it by weight? Volume? How do you know if your ratio is correct? Do you use a scale? I can just picture my wife sitting down to 'do her business', then weighing the bucket, then adding peat at a 30 to 1 ratio....

An excellent question. I've wondered the same thing in the past myself. I think technically to know the ratio you'd have to calculate molar masses and such, dependent on volumes and densities of compost ingredients. Which means the answer in reality is "you guestimate!"

Fortunately, composting is a very forgiving process. If you start with a bunch of N ingredients, like our humanure, you know that you need to add C to be safe. If on the other hand you start with a bunch of C, a giant pile of autumn leaves perhaps, then for best results you should add some N, like a bit of manure or a good amount of green grass or vegetable waste. In time you can adjust by adding more of one of the other if you don't like your results. There are charts online to guide your guestimations, like the one I have recreated below from http://www.homecompostingmadeeasy.com/carbonnitrogenratio.html. For example, this chart tells me that, as your carbons go, sawdust and wood chips are SUPER carbon rich compared to, say, dry leaves. So I should use them more sparingly as a compost pile ingredient. Or to look at it in another way, if I have a giant pile of wood chips I want to get rid of by composting, I know I need to add even more nitrogen ingredients than I might think if I want to the process to be optimal in terms of time and temperature. (In reality, I'd actually use the woodchips as mulch; I'm a believer in composting in place, not in shoveling piles around... but that's a conversation for a different thread.)

But the most important thing is to remember that, given enough time, EVERYTHING composts. It just might not get their as optimally as you'd like if your C:N is off. So leave your giant pile of brown leaves alone, and you will still get compost, it will only take longer for being nitrogen starved. And if you were counting on killing weed seeds from the heat, you might not get enough heat. Opposite example: leave your pile of green grass clippings alone, and you will get compost, it will only be nastier and stinkier along the way than if you'd added some more carbon rich filler.

The website I listed provided these rules of thumb: a 2-to-1 mix [I think they mean by volume] of Greens to Browns should get you close to a 30:1 C:N ratio, adequate enough to get a hot pile. A 1-to-1 mix should get you closer to a 50:1 C:N Ratio, adequate enough to get a warm pile.

For humanure composting, I would guestimate generously with the carbon additions, just to be on the safe side, shooting for at least the 1-to-1 mix. If a scoop of sawdust would likely suffice, I might add two for the hell of it. I don't care if my humanure is drier and slower to compost, so long as it doesn't stink. I've done humanure on my own site in the past - we just guestimated a generous load of carbon per poop and came out quite fine. But it is good to know that the material you're using as a carbon is in fact higher on the carbon side of that 30:1 C:N ideal. Based on the info below, as I suspected, they classify coffee grounds as a "green" (i.e. nitrogen rich). Likely less so than the poop, so adding grounds still moves you in the right direction, but perhaps not the best choice if that's the only carbon you're adding, as you'd have to add a whole lot more.

GREEN (Nitrogen)
Aged Chicken Manure 7:1
Food Scraps 17:1
Vegetable Scraps 25:1
Coffee Grounds 25:1
Grass Clippings - Fresh 17:1
Fresh Weeds 20:1
Rotted Manure 20:1
Humus (soil) 10:1
Seaweed 19:1

BROWN (Carbon)
Leaves 60-80:1
Straw, Hay 90:1
Sawdust 500:1
Woody chips & twigs 700:1
Shredded Newspaper 175:1
Nut shells 35:1
Pine Needles 80:1
Corn Stalks 60:1
Peat Moss 58:1

Count me in on another person who doesn't worry about the ratios so much. I use enough sawdust to keep things from stinking and to absorb urine. I just keep building more pallet compost piles as I need them. My oldest is about 3 years old, probably won't get around to harvesting anything for several years yet. I can tell you that I probably use more carbon than is proper for a good ratio, given that my piles never heat up and if you dig down in the older ones you see a lot of sawdust still.

However, I figure that with enough time, the redworms in the pile (I put them in after year 2, and they have thrived), and when I plan on using the compost I will use it appropriately (and not grow lettuce in it!).

Regarding the carbon material - whether or not sawdust is a good material for you highly depends on availability. We have a local sawmill that will load up a pickup truck for $25, that's about an 8 month supply for me easy. That's win-win. If I couldn't get that, I'd probably do some kind of combination of dirt and carbon material, knowing that I'm not going to spend the amount of time needed to grind up anything super fine so I figure, a layer of carbon and a layer of dirt would be ok. But that's really more if some crazy thing happened and I couldn't get sawdust, which is unlikely. We have three major sawmills within 40 minutes of my house, so I don't think that will be a problem.

i am building an classic cedar outhouse up the hill by my garage
in the bottom of the "pit" i will put an open rubber maid barrel
with fine holes drilled into the bottom

after each use i will drop a good scoop of Purina WORM chow
on top of the night soil followed by maple leaves

from my recycled freezer now housing my compost worms
i will have carried up a small container of breeders to seed into
the pit to keep the operation going.

i will use a french drain with wood chips/ saw dust /charcoal
separately for number one's.

1- separate pee so you can use earth worms for composting. They do not like pee.

One of my best local plants around with prickly pear, but not for the same job...

Fennel: good for your cleaning and put it down there with the poo.
The finest leave AND fine for the job!
A bunch in your hand, not 1 leave...

Here I have "vinagrera". You might have something with the same caracteristic:
It has a loooooot of seeds, and those seeds dry so that they look like wood chips in size.
I can collect a bag very quick.
If they compost, then they self-seed less....

Also, what is on the ground under pine needles: nearly composted.

One person already kind of answered this but I want to throw the question out anyways for clarification.
What about confetti shredded newspaper and/or junk mail for carbon stock? Anyone using it currently or for a long range option? I am running into brick walls trying to find wood chips/sawdust - have exhausted all avenues and short of spending a ton on sawdust from the local mill (which defeats the point, in my opinion, of transitioning to a low cost humanure system) I'm thinking about newspapers confetti shredded.
Thoughts?

Lindsey Jane wrote:One person already kind of answered this but I want to throw the question out anyways for clarification.
What about confetti shredded newspaper and/or junk mail for carbon stock? Anyone using it currently or for a long range option? I am running into brick walls trying to find wood chips/sawdust - have exhausted all avenues and short of spending a ton on sawdust from the local mill (which defeats the point, in my opinion, of transitioning to a low cost humanure system) I'm thinking about newspapers confetti shredded.
Thoughts?

I'm thinking newspaper is a potent carbon - 175:1 according to my copied chart, above - so it will get the job done.  I'm thinking newspaper would be better (coarser, more absorbent) than office paper or junk mail.  I'm thinking shredded newspaper would work better than whole crumpled sheets of newspaper.  I'm thinking that since shredded newspaper is both less carbon-heavy and less dense than sawdust, you should use a larger scoop of it per poop than you would use sawdust.

So, assuming you have a free supply of newspaper, I don't see why it wouldn't work.  But you will have to be okay with the time and expense spent creating large volumes of shredded paper.  A quality home paper shredder is an investment.  A cheaper home paper shredder if you catch one on a great sale will surely get the job done, but for how long until it dies?

I use potting soil or peat moss.   Mostly potting soil.   The main reason I use it is because it is cheap and helps break up my clay soil.

Just as another source and data point.

We ran a humanure system for 2+ years.  My carbon source of choice was wood pellets.  Because of the bulk, -most-  wood pellets are produced locally sort-of.  Pretty local?  Making the pellets becomes uneconomical if you have to ship the raw materials or finished product very far.

Widely available at menards, lowes, home depot, and typically five dollar per bag (40 pounds I think).

They swell when wet and absorb moisture pretty well.  The smell was not unpleasant.

If you can't find anything more local, and less expensive, this is not a bad option.