Soil Banking With Biochar: proposition for a migrating latrine system aimed at permanent soil improvement

"The idea is to have a sort of trench system that would serve both as a latrine, and as a means of permanently improving the soil."

This proposal is built around the concept of using charcoal to permanently improve soils.  If you’re not familiar with that idea, a little reading on biochar might be helpful.

(EDIT: Ok, I just posted this yesterday, but the original title sucked, so I had to take action.  The more I've thought about this idea today, the more I'm inclined to think that viewing it as just a latrine is way too limiting.  A system of soil improvement like this could serve to accommodate all sorts of rubbish and organic refuse.  I always thought that if I built a nice outhouse someday, that I'd make a sign for it that said Bank of Fertility (make a deposit:).  I like that concept.  I'm going to go with the term Soil Banking for the concept of a migrating soil improvement  system using an open trench.  While making daily deposits of doodie makes eminent sense for such a system, there are so many more things that could be tossed in the mix.  All people who live in the country that don't have access to landfills, have rubbish heaps or pits of some kind.  What I'm proposing is that we use that open pit, and the material added, to a high level of advantage toward the end of permanent soil improvement.  At this point, I can only see a big open pit, placed in the right area, to be an outstanding opportunity.  The idea of permanent soil improvement, made possible by the addition of charcoal, is really compelling.  Dead animals and parts, rotten wood, old natural fiber clothing, shells, bones, ashes, seedy weeds that are best not put in to the compost, anything else that plants or soil life can feed on that the chickens can't eat, or that we don't want to put in the compost for whatever reason, and of course poo and charcoal, all added as they occur.  And of course adding whatever other amendments, like lime, rock powder or trace minerals might make sense too, depending on circumstances.  Over many years, this system could add up to an ever expanding bank of super soils that will probably continue to be superior for decades, if not for centuries.  So there it is, Soil Banking.  "What should I do with this dead maggoty possum?"  "put it in the soil bank with a few scoops of charcoal and some dirt"  "yeah, okay, I was going there to make a deposit anyway!" "righteous dude, high five!"  Now back to regularly scheduled programing.)

I’ve been knocking this idea around in my head for a while.  Actually, maybe it’s been knocking me around it just want's me to think that I'm knocking it around.  It started when I was thinking about ways to use the pit after pit burning charcoal in a long trench.  The obvious use was to bury the biochar in it instead of digging another hole for that.  After all, it’s one thing to make all that char, but then you have to dig it into the soil, which is a butt load of work.  In this climate, outside of irrigated garden beds, I think getting the char pretty deep is probably a good idea.  After june, soil moisture is scant near the surface.  If the char was buried lets say only 12 to 18 inches deep, that puts it in the zone where roots are mostly on idle for the summer.  No moisture= no root activity to speak of.  Charcoal is a great retainer of moisture, but it’s not that great.  I’m talking about unirrigated areas for orchards and perrenials, or maybe for dry farming crops.  If the char was more like 3 feet or 1 meter deep, it would be of much more benefit to plants in the summer season.

Tree planting site, modified by digging a large pit to 2 feet deep, burning charcoal in it, crushing the charcoal and mixing it in as the pit was re-buried.
Tree planting site, modified by digging a large pit to 2 feet deep, burning charcoal in it, crushing the charcoal and mixing it in as the pit was re-buried.

Once I thought about it for a bit, I realized it doesn’t make a ton of sense to keep digging new pits just to burn the charcoal in.  it’s not like I’m probably doing the soil any favors by cooking it anyway.  A central permanent burn area, with a more permanent pit arrangement would probably make more sense, or just burning by any number of methods wherever the wood happens to be.  Charcoal is light, so moving it is not an issue.  Moving brush and wood is a whole lot more work.  In most situations, it’s probably not relevant how the wood is charred, the idea of using the burning pit as a latrine was just a path into this idea.

So let me just hit you with the basic idea and then we can bat the details around a little.  The idea is to have a sort of trench system that would serve both as a latrine, and as a means of permanently improving the soil.  Once the pit is dug, there are limitless possibilities for amendment with all sorts of substances, and for changing the soil’s physical composition.  That’s pretty neat!  Also, normally, it would be a fair amount of labor to mix in all of that stuff all at once.  As a latrine though, you’d be mixing it in gradually day by day while doing something you have to do everyday anyway.  Lets say you wanted to end up with about 20% charcoal in the soil.  One poop, one scoop of charcoal, four scoops of dirt and small amounts of whatever other substances you might want to toss in there like lime, wood ashes, sand, phosphate fertilizers, trace mineral fertilizers, organic matter, etc.  I’m already digging holes for the current pit latrine used here on the land, but this system would utilize part of that labor to a more useful end.

This system makes sense to me for soil improvement with biochar under my type of conditions.  It seems likely that the terra preta soils of the amazon might have been made with some similar approach... like pits into which compostables, broken pots and excrement might be disposed of and covered gradually with dirt and charcoal.  I'm not experienced enough with using biochar here to be totally convinced this method will be worth the effort, but I think there is a very high probability that the results will be awesome, easily high enough to jump right in and make the investment to try it.

I’ve never really gotten the latrine scene together here.  We’ve always used a pit toilet- dig a pit, drop in a little dirt or organic matter here and there till it’s full, and move on.  I’ve tried to put them where I want to plant a tree, but it doesn't always work out.  The one site I have actually planted directly on, the tree died, twice even!  That might just be due to drought, but suffice to say, it hasn’t worked out very well for me as a system.  Also, I’m not convinced that even a pit full of manure is really a very permanent soil improvement, and it will have a limited window of fertility.  I’ve thought to eventually build something like the Ecosan drying pit toilet system, but that could be some time away in the future.  Thinking back now, 8 years of being here most of the time day in and day out, I could have improved a lot of soil using my new proposed system.  The pits would fill up quickly, because so much dirt would be added back daily.  It’s a lot of digging, but it’s easier to dig a wide trench than to dig a single deep and narrow pit.  Also, it is assumed that soil improvement is an important goal, so the digging is not superfluous work.  It is also spread out over much time.  Consider digging char into a 40 foot long x 5 foot wide x 3 foot area all at once versus over the course of a year or so.  The trench could be dug in sections as needed, or when convenient.

This walnut tree, flanked closely by two latrine pits is starting to take off this year. I think the roots have probably hit pay dirt. Overall though, planning to plant trees over latrine sites hasn't worked out that well, and it's a short term soil improvement.
This walnut tree, flanked closely by two latrine pits is starting to take off this year. I think the roots have probably hit pay dirt. Overall though, planning to plant trees over latrine sites hasn't worked out that well, and it's a short term soil improvement.

In the days before plumbed toilets, public latrines were a major issue in population centers.  I’ve smelled enough latrines to know how horrid the stench must have been.  It was proposed to use charcoal as a deodorant and the resulting sludge sold as fertilizer.  I think this method was probably successful where implemented, but it wasn’t too long before they started washing it all away into rivers and off to the ocean, which of course we mostly still do today, just in a somewhat more refined, but also much more resource intensive way.  Point being, charcoal is the ultimate deodorizer.  Imagine an outdoor latrine with no odor.

Having been called on that day to attend a meeting of the Board of Health, held at the workhouse, I was at once struck with the intolerable and sickening effluvinm which, arising from the sewers, cesspools, and privies, pervaded every part of the establishment; and which, with the chlorine, which was being evolved in every direction for the purpose of correcting it, formed a compound of villanous smells, which no stomach but one accustomed to it could for a moment tolerate. Your very active and efficient inspector, Captain Hanley, told me that he had done everything that could be thought of, and had spared no expense to try and have the nuisance abated, but that all his exertions were useless. I then begged him to send down and purchase a few loads of peat charcoal, which were selling at the market; and having told the master how to employ it, the suggestion was at once adopted, and though the material was not of the best description, nor “ recently prepared,” in a very few hours the most delicate and practiced nose could not have detected the slightest offensive odour. Since then the master, with very praiseworthy attention, has had a large pit of the charcoal prepared every week, and by its occasional use through the grating of the sewers, and by sprinkling it over the nightsoil in the privies, the workhouse is, as far as entire freedom from every noxious and offensive effluvinm, a model to every other in the kingdom. In every respect the results have been most satisfactory. Instead of paying from five to ten pounds, every half year, for having the privies cleansed; and having itself and the whole surrounding neighbourhood at the same time poisoned for weeks by the intolerable stench ; the establishment has that task now performed by the paupers, without the slightest reluctance on their part;—and the contents of the sewers, cess-pools, and privies are now collected into inodorous and innoxious heaps, or mixed with the other refuse of the workhouse until removed by the contractor; which, before, he absolutely refused doing, but which he now considers the most valuable portion of what he contracted for.

Also, adding significant amounts of dirt on top of the daily deposits would completely cover them, so flies would not likely be an issue either.  Ov course you could tweak the amount of soil added in order to either improve more soil in a shorter time, or to make the latrine last longer to the end of digging less.  I’m seeing this more as a way to improve a lot of soil at this point, so thinking of finding the minimum amount of poo to maximum amount of dirt and charcoal added back, while still ensuring good results.

So, one issue with burying charcoal in the soil is that it is a nutrient magnet.  The first time I did it, the lettuce I planted afterward failed to thrive.  It was pretty bad, I mean it barely grew and produced nothing really edible.  The most recent garden bed I amended with charcoal, I added a lot of chicken manure and compost teas to as it was being dug in, in order to charge the charcoal up so it wouldn’t just suck everything up leaving nothing for the plants.  That bed is doing well in it’s first year.  Once it’s charged up, this property of charcoal to catch and hold nutrients becomes a benefit rather than a liability, possibly the most important property of biochar, but it must be charged somehow.  The latrine system should provide a nutrient rich environment to charge the charcoal up as it’s added.  I would probably add stuff in this order:






organic matter (if added at all, probably a little forest duff at least, if just for innoculation with diverse soil organisms).

The current outhouse structure can be carried by 4 people or rolled on logs by two, but it is far too heavy and awkward to be moved frequently by one person.  I’m thinking that a more tent like arrangement would be better suited to my trench latrine plan.  I though originally of some rails that the covering slid on, but I think that a more simple and elegant solution is needed. I’m thinking for my style a couple of planks with a space in the middle to use as a squatting toilet and a light frame covered with a section of plastic billboard tarp could be plenty cozy enough.  The tent covering would need good anchorage from winds... maybe sand bags or cinder blocks which bungee to the frame?  We’ll see.  No need for a door most of the time, depending on the site I guess, but an old sheet should work okay.

Ye 'ol outhouse, a loo with a view.
Ye 'ol outhouse, a loo with a view.

The great majority of us are wasting the nutrients we excrete.  This state of affairs makes not a bit of sense at all.  For homesteaders, finding some way to utilize the nutrients that are leaving our bodies seems like it should be something of a priority.  We can’t afford to hemorrhage nutrients out of our living systems and we shouldn’t even if we can re-import them from somewhere else.  While saving urine to use as a fertilizer will catch the vast majority of the useful plant nutrients leaving your bodies, and is a great first start, doodie also has a lot of good stuff that can be turned to advantage.  This system seems very promising to me.  It’s going to be too much work for some people, but for tough and scrappy homesteader types and less “developed” cultures and areas, it is probably fine.  The prospect of the opportunity to create super soil zones by utilizing immediately available resources and a trickle of labor from already daily activity, gets me all hot and bothered and would light a fire under my ass to go start digging if said ass wasn't glued to a chair most of the time.  I mean that shit is exciting people!

My proposal is really for a system which modifies the soil to quite a depth, but I suppose it could be used in a shallower form too.  For a system that required more upfront investment, but less labor over all, the ecosan system with charcoal added to the ash might be a good way to go.  Briefly, the Ecosan system uses two pits.  Urine is diverted out of the system and collected in containers for direct use.  Each time a solid deposit is made, a handful of ash is added to cover it, help dry it out, and alkalize it, all of which kills off microorganisms.  The collection chambers are ventilated to encourage drying.  Once one pit is “full” it is closed off to dry completely, and the other side is used.  By the time pit two is full, six months or more later, pit one is completely dry and innocuous.  If charcoal was added, it would pre-charge the char as well and the whole lot could be pulverized as a very rich, fertilizer for use primarily on annual crops.

Here at Turkeysong I could see running both systems eventually.  I’m pretty tough, and am used to inconvenience from years of re-training my entitlement set points.  I'll spare you the details, but trust me, I have gotten through the worst of times with the most inconvenient toilet and living situations, like no toilets at all and extremely ill, rain or shine, day and night.  But, um, honestly, tough or not, I’d rather sometimes have a close outhouse to visit!  Inconvenience isn’t the goal or noble in and of itself.  Sometimes simple solutions are still the most elegant ones though and being constantly besieged by convenience can make us into weak and whiny people.

I’m pretty opposed to the idea of indoor bathrooms.  Digging little holes in the forest or crapping in a trench might seem crude, but pooping in your house just seems plain uncivilized to me.  I could see both the Ecosan and trench systems eventually operating simultaneously in a place like this.  The cozy, luxurious Ecosan, (maybe with a door, or a light and some reading material even!  How about a stereo, wide screen t.v... wifi...) close to sleeping quarters for late nights and rainy days, and the biochar trench latrine for the rest of the time, or for special soil improvement projects.

I hope this idea will appeal to someone enough to try it out and we can see what the profits and pitfalls might be.  Obviously, making a bunch of charcoal is in order, quite a lot actually.  The good thing is that once it's made, it keeps forever.  I managed this past winter and spring to experiment a little with the top down burn pile and pit methods of charcoal production.  Both are easy and accessible and can be used with random scrappy brush.  I’ll leave you with the super condensed version of both, but stay tuned for more on those in future posts or videos.

Top down piles:  Pile brush in a tall narrow pile.  A tall narrow pile is more work, but it burns better than a mound shaped pile.  Light from the top which produces way less smoke.  Throw unburned pieces from the outside into the center as burning progresses.  When most of the wood is charred and no longer flaming, douse with water.

Top down pile, ready to light as soon as rains start.  See this pile burn here!

Top down pile, ready to light as soon as rains start.  See this pile burn here!

Top down pallet pile.  Notice how little smoke there is.

Top down pallet pile.  Notice how little smoke there is.

Pit:  dig a pit with sloping sides.  For long wood, dig a long pit so you don’t have to cut the wood.  start a long narrow fire in the bottom.  Add wood in layers.  When burned down and not producing much flame, add a layer.  try to cover the layer below well, but each layer should be only about one stick thick, not piled up.  this system doesn't work very well with very tangly torturous type brush.  Conifer limbs with the needles on are fine, but oak brush with branches pointing in every direction and taking up a lot of space in every direction needs to be broken down a bit.  This system works by smothering the previous layers with new fuel.  Just remember to try to have the new layer close down on the top of the old one to smother the coals below so they don't continue to burn.  When very little flame is left and the pit is full, douse with water.

Burning charcoal in a trench. There is a trench, this is the end of the burn when it's full of charcoal.  Video here.

Burning charcoal in a trench. There is a trench, this is the end of the burn when it's full of charcoal.  Video here.

I think the pit is probably more efficient in the wood used to charcoal produced ratio than the top down pile style--- but it seems to require a little more work and attention too.  I’m not really sure yet.  In both cases, don’t wait for every single piece of wood to be charred before extinguishing.  You will end up with some un-charred wood, but you can always re-burn it.  If you wait for every single piece to be charred before extinguishing it, the wood that is already burned down to coals is rapidly turning to ash, effectively reducing the total charcoal yield.

I’m somewhat annoyed with myself for not "having my shit together" already.  But, when we have to always be pioneering new ideas and systems, it’s not always easy to get it together, and I have a lot of challenges to face so I'm cutting myself some slack.  I’m convinced that urine diversion is the first step and anyone who has hung around this blog much knows I just won’t shut up about that.  Next, something like the ecosan system and/or a system like I’ve just proposed that amends soil as it goes along, should make maximum use of our leavings.  And that should be the goal.  We are so fixated on disposal, and the idea of excrement being a valuable resource is so totally foreign, that it is often difficult to find language that can really get across the way we should truly be thinking about the issue.  Like I said, it makes no goddamn sense to extract the very essence of the soil, that which plants make their bodies with, and then throw it away.  Not only should homies like us be building our infrastructure around a new paradigm, but as a society, we should be thinking toward decommissioning our old systems and implementing new ones that honor our daily discharges as the very valuable resources they are.  My trench latrine will certainly not appeal to the timid, but it can’t be that hard to come up with a design that tops the current practice of pissing and shitting in a ceramic bowl of water in the house!  Like omg, that shit is nasty.  And said bowl has to be cleaned by some unfortunate person, like ewwwwww.... If we can put people on the moon as they say...


*Dig a trench or pit, up to a meter deep.

*Use a light moveable cover.

*I'll probably use planks for a floor with a space left open to squat over.  An elegant solution and highly flexible.

*Add charcoal, dirt and/or other nutrients and amendments with each deposit. shoot for 15% and up of charcoal if possible.

*Find a poo to dirt and charcoal ratio that makes maximum use of droppings and fills the hole quickly.

*If a trench is used, expand the trench as the previous section is filled up.

*Be stoked that you've done something agricultural that may actually last for a really long time, unlike standard impermanent soil improvements.

Posted on July 29, 2014 and filed under Garden Stuff, Uncategorized.