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Burning feces at very high temperatures

 
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I know this may be a relatively unpleasant topic for some, but I know that throughout history there have been some cultures that used manure for various sorts of fires. Most notably to me is the Mongols, who conquered much of the known world using swords and spears forged over fires made from dried horse manure. Horse manure contains a lot of grass though, and so obviously it gained a lot of its burn characteristics from that cellulose content. Aside from containing carbon, feces also contains a high amount of nitrates that might not burn at regular temperatures for a wood fire, but might do so under extreme heat. This makes me wonder if inside a "rocket" type stove, manure could be burned and the nitrates would be able to form nitrous oxide, which in turn might further oxidize carbons in the exhaust stream providing additional chemical reactions beyond what a normal fire produces.

Does anyone have experience burning manures of any kind? Does anyone have any scientific expertise on this matter with regard to the chemistry of the reactions? We have a large and steady stream of cat wastes available to us that are in pine litter, and would like to know if we can incinerate them and if there'd be any benefit to doing so.
 
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Dangus McFinghin wrote:I know this may be a relatively unpleasant topic for some, but I know that throughout history there have been some cultures that used manure for various sorts of fires. Most notably to me is the Mongols, who conquered much of the known world using swords and spears forged over fires made from dried horse manure. Horse manure contains a lot of grass though, and so obviously it gained a lot of its burn characteristics from that cellulose content. Aside from containing carbon, feces also contains a high amount of nitrates that might not burn at regular temperatures for a wood fire, but might do so under extreme heat. This makes me wonder if inside a "rocket" type stove, manure could be burned and the nitrates would be able to form nitrous oxide, which in turn might further oxidize carbons in the exhaust stream providing additional chemical reactions beyond what a normal fire produces.

Does anyone have experience burning manures of any kind? Does anyone have any scientific expertise on this matter with regard to the chemistry of the reactions? We have a large and steady stream of cat wastes available to us that are in pine litter, and would like to know if we can incinerate them and if there'd be any benefit to doing so.




I don't know the science behind this but I'm pretty sure you could do it.  Here is a video that might lead you to some other resources...this company in Kenya is making briquets out of human waste.   Another video is a company in Milwaukee making fertilizer with human waste.



 
Dangus McFinghin
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Thanks for the reply! Interesting!!! We're basically using saw dust as kitty litter. Its horse bedding, but its kiln-dried pine. I was thinking about putting it into a hydraulic press that has an outflow line at the bottom to drive out the liquids. Seems really wasteful to kiln-dry the stuff. Kenya has so much sun, I'm shocked they aren't using solar systems to desiccate the wastes. The raisin industry uses the sun to do a similar job on grapes, but that obviously has a much better odor lol....   I was thinking about basically making logs or pellets out of it and then stacking them to dry outside somewhere sheltered. Might need to put screen around it to keep bugs off of it though. Our kitties produce like 3 tidy cat buckets packed full of it every 3-4 days so it would potentially produce quite a fuel supply for us if we could utilize it.
 
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As for cat litter we used to use the recycled paper stuff and put it directly on the fire . Booof gone no problems no faff on .
For human waste better off composting iit I am sure the humanure book is available free as an ebook otherwise it's generally too wet to do much with , you need either a lot of it or a lot of work to do anything else with it in my opinion.

David
 
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There is some historical evidence that bochar made of poo is incredibly benificial to the soil.
Kitty poo being pretty biohazardous, I would consider it a great candidate for making into biochar.
To deal with the wetness, use a retort system.
It will take some fuel to get it started, but the gasses driven off during pyrolysis include water vapor.
I've been using an old steel tool box as my retort, it's about shot.
A stainless steel steam table pan has been used inside woodstoves,to good effect.
You gain fuel and biochar,and no drying is needed.
I've done this with green twigs and chicken bones,it's very forgiving.
 
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All over India, Nepal and Tibet, cow dung is dried and used for fuel. The difference, though, is that cow and horse dung are not unpleasant to handle, unlike cat and human feces. Dried cow dung is hard and dense, and doesn’t smell bad. The smoke from it is mild and sweet, somewhat like apple wood.

Personally I wouldn’t like to handle human or cat products enough to dry them and then burn them. They smell bad while drying.

Composting them is easy. There are many books and sources online about composting humanure, Joe Jenkins Humanure Handbook being the cult classic, and available online, with lots of information in it. In my experience, cats like using sawdust as litter, and the combination would easy to dump in a bottomless slightly sunken barrel to compost along with some other things for variety.
Toxoplasmosis is a parasite carried in some cat feces, and is the cause of the well-known warning against pregnant women handling litter boxes. But recent research has also implicated toxmoplasmosis in schizophrenia, increased suicide risk in women, and other problems.

http://www.theatlantic.com/magazine/archive/2012/03/how-your-cat-is-making-you-crazy/308873/
 
Dangus McFinghin
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Toxo is certainly a serious threat in very limited circumstances. Its highly important to understand that cats only shed the oocysts once in their entire life, and that's only if they have toxo(not all cats do). Ours have all been with us 4 years or more and so definitely are not a toxo threat. Wild cats like bobcats and cougars also function as reproduction hosts for toxo, but its worth noting that while sexual reproduction of the pathogen can only occur in cats; asexual reproduction can occur in a variety of settings. It is a very hardy pathogen and may persist in soil for a long period of time. Soil is certainly the main vector by which people become infected either through poor handling practices or failing to wash produce. Toxo should be taken seriously, but at the same time it is worth understanding where the threat actually tends to come from. Incinerating their wastes is a sure-fire way(pun intended) to ensure their wastes do not infect soil. One should never handle cat wastes with bare hands though for a whole bunch of reasons. I would even recommend you avoid handling it with gloves more than necessary, preferring instead to interact with the material via tools.

I have been doing a lot of research on the idea of making biochar from this and discovered there's a number of others who use wood-based litter who are already burning it. None seem to be using a rocket stove though. Its going to take me a bit of time here to rig up the compactor for it, but I will be compressing it into pellets/rods that will be sized to be ideal for RMH use. My rocket heater will be drawing outside air and will be closed completely to the interior atmosphere when the fuel door is closed. Any latent moisture should evaporate in the feed tube due to the residual heat from the fire box. The bulk of the moisture will be driven out by my compactor through its drain line. Our kitties produce so much litter though that we should have no trouble heating our place all winter just off their litter if we can develop a practical way to manufacture the fuel pellets/rods
 
Dangus McFinghin
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For anyone curious about this experiment, I found an interesting discussion from some British cat owners about burning wood-based kitty litter for heating fuel.

http://www.recyclethis.co.uk/20080826/reusing-wood-based-cat-litter-as-heating-fuel

It sounds like result vary, but some are very happy with it. Its interesting that one of the people in that discussion was talking about compressing it in a section of pipe using a press. That's exactly what I was talking about doing. Only in his case the pellets he created didn't hold together well, which is most likely because he was leaving the feces out of it.

I've been having trouble sourcing materials around here for my J-tube. I'm still fairly new to this area and don't know where to find things like I would have back home. Google seems to be about useless for finding local sources of refractory materials and the scrap yards are not answering me by email yet. I'll need to call them when I get a chance. I do know a source of white clay kitty litter and the more white clay is, the higher its melting point tends to be. I have a lot of silicon dioxide in the form of "crystal" kitty litter. I'm going to crush the silicon dioxide into a powder and mix it with the clay to raise its melting temp. I'll probably coat the inside of the riser with pure silicon dioxide powder for maximum heat resistance. So the stove that may end up burning kitty litter fuel may also be made from kitty litter....
 
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I've been wondering if I could recycle cat litter by heating it enough to burn out the cat waste but not hot enough to fire the clay.  I have kilns, but I don't know what temperature, or if it is safe.
 
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Joan Eckard wrote:I've been wondering if I could recycle cat litter by heating it enough to burn out the cat waste but not hot enough to fire the clay.  I have kilns, but I don't know what temperature, or if it is safe.


After 30 years burning 5-6 cords/winter in my Blaze King and using heavy clay cat litter, I finally found out about wood pellet cat litter, but it was already early March.
In Anchorage it’s cheaper by volume than clay , by a factor of 2 or even 3. I had started throwing cat poop in the Blaze King previously, but with the first batch of used Felinepine I bagged it in used paper grocery bags and threw it in. It burned well. Fortunately when it’s cold = north breeze there’s nothing except tide marsh and ocean to the south so smoke odor isn’t a problem.
I’m kicking myself for not thinking of this decades ago.
 
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PS
I never even tried putting clay litter in the stove except as “almond roca” adhering to poop picked out with TP or paper towel.
The woodstove burns thin polyethylene used grocery bags no problem with poop inside them.
Fresh poop is 70-75% water; therefore ~ 1 kcal = 4 btu/gm; minus heat of vaporization of water. Dry poop is 4 kcal = 16 btu/gm, just like sugar.
 
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During my degree I had some contact with a research team who were looking into safe burning of human waste. They were taking the dewatered sludge from waste water processing plants.

Their test bed used fluidised bed technology. Imagine air being forced up through a cylinder from lots of small holes near the base. Just fast enough to slightly lift the burning particles so that they move like a fluid. I think they also included some inert ceramic beads, which stores heat and helped balance the heating cycle so that it didn’t oscillate wildly.

The end result was an incredibly hot and clean burning reactor, with exhaust gases that could be used to power pretty much anything. It was a very neat setup.

They went to all this trouble because existing solutions were not clean enough, and and were more difficult to extract the energy from.
 
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The problem is the solution appears again...

It never occurred to me I could turn these annoying cat droppings into something useful.

I will ponder the methodology I will use to collect, dry, and burn said poop to prevent it from being stuck to the bottom of our shoes, boots, and other unwanted places while I wait for the best timing to talk to the cat owner...
 
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Sometimes my brain makes a 360 degree turn...it is doing that now, on this topic.  Sure, in India the cows are viewed as Sacred and they roam at will; their droppings dry out completely and are not only easy to pick up, but vital as fuel since there is not cuttable wood for all those fires, and it is free.  But that's India.

Here we are talking about getting rid of human/pet waste; it is not dried and it is a stinky biohazard; also as someone pointed out, it is easily compostable.  We need to make the soil more and not less fertile; we are "permies" so if we took it out it should go back in, right?  

As for cow and horse dung, my goodness, why burn it when it is such a great amendment?  Wood burns fine, and is renewable. I'd be interested in learning how to compress the cardboard from all of my Amazon boxes into logs; though I suspect they really want to be lasagne outside, cuz I just don't wanna work that hard when we have so much wood around us here.  Not the case for everyone I am sure but we live in Woods!

 
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