[Stoves] Drawing down the dung pile
Kevin
kchisholm at ca.inter.net
Tue Dec 7 07:15:06 CST 2010
Dear AD
Your point about the difference between the dungs from different animals is a very important one; some may be readily processed for use as a superior fuel, while others may present difficulties.
Your point about the "manure tea" being an imbalanced fertilizer is also important. However, there is a large body of very successful experience showing that manure teas are beneficial. At the very least, such manure teas will provide at least some fertilizer effect, and the need to buy fertilizers will be reduced.
As mentioned elsewhere, I have heard somewhere that elderly Indian Women who have tended dung stoves seem to have a very high incidence of blindness, compared to women tending "non dung" stoves. Have you seen anything that would support or negate this belief? Have you seen any health reports relating to emissions from dung stoves that identify illness conditions that could have been caused by dioxin presence?
(See: http://aje.oxfordjournals.org/content/153/11/1031.abstract
http://oem.bmj.com/content/55/2/126.abstract
http://humupd.oxfordjournals.org/content/7/3/331.abstract
Best wishes,
Kevin
----- Original Message -----
From: Anand Karve
To: Discussion of biomass cooking stoves
Sent: Tuesday, December 07, 2010 3:58 AM
Subject: Re: [Stoves] Drawing down the dung pile
Dear stovers,
dung from herbivores is of two kinds. The ruminants (bovine cattle, water buffalos) chew cud and therefore the dung consists of very fine particles. Filtering them out from a watery suspension is a bit problematic. I think that a filter press might serve the purpose better. The dung of non-ruminants, e.g. horses, donkeys, elephants (elephants belong to the category of domesticated animals in India) contains longer fibres and it is easy to clean it by washing and straining it through cloth. Allowing the dung tea to flow into the field is O.K., but it may not have all the minerals that plants need. After all, when animals eat the plants, their bodies extract not only the digestible organic carbon, but also all the minerals that the animal needs.
Yours
A.D.Karve
On Tue, Dec 7, 2010 at 1:48 PM, Kevin <kchisholm at ca.inter.net> wrote:
Dear Crispin
The basic concept I propose is as follows:
1: Slurry the dung with water
2: Filter the water and any solubles and press the remaining dung cake.
3: Shape and dry the remaining dung cake
1: Slurry the dung:
Mix the dung with water, to an "adequate" degree of dilution, such that most of the solubles will be dissolve in the wash water. If water is readily available, and if there is a large need for irrigation water for agriculture, then single stage washing can probably be used. If water is scarce, and if the scale of operation is small, it might be better to do a "two stage wash",
2: Filtering
Separation of the water from the slurry can be done in a number of ways. The first stage of water and solubles separation is probably best done by simple decantation. Floating material can be skimmed off the top, and relatively clear liquid can then be drained off. However, it should be filtered through cloth, to ensure that a clear liquid is produced, if the manure tea is to be used in a "fertigation system" involving relatively small distribution nozzles that may be prone to plugging. The remaining bottom material will still be very wet, and is probably best dewatered using a filter press system, or filter bags.
3: Shaping the washed dung.
Depending on the desired end use, the moist washed dung can then be shaped to the desired final shape, and then dried. Obviously, many shapes are possible:
* Briquettes
* Pellets
* Sheets
* Etc.
The washed dung will tend to be high in lignin, and relatively low in cellulose, in that the animal would have digested much of the original cellulose in the feed. Depending on the degree of washing and the characteristics of the washed dung, it may, or may not have sufficient binders to hold the washed dung together in the desired shape. Experimental work would be necessary to determine if added binders would be required, and quantities required.
Following are my comments on the replies received to date....
----- Original Message -----
From: Crispin Pemberton-Pigott
To: 'Discussion of biomass cooking stoves'
Sent: Monday, December 06, 2010 1:48 PM
Subject: Re: [Stoves] Drawing down the dung pile
Dear Doctor Dung
The offer is welcome. Perhaps the answer is to briquette it then, using the process to wash it. Leach, I can see, standing in a perforated container.
# I would suggest that teh washing must be done before briquetting. Frank (see below) suggests one good looking way to wash teh dung.
Water is often a simultaneous constraint but there will be places where dung and water are available, which means a market.
# The process would be of greatest advantage in connection with a farming operation, where the leached solubles can be productively used for both watering and fertilizing of crops. If tehre is not such a farming use for the washed solubles, then there could be a significant disposal problem.
Remember that in this region the stoves will all have a chimney because space heating is desperately required. Leakage will be a more important consideration than emissions (though obviously I favour reducing emissions as well).
# This would certainly be helpful for the occupants inside teh house, but if a lot of dung is being burned, and if the location is prone to inversions, where teh smoke "hangs low", then there could be a community pollution problem.
----- Original Message -----
From: "frank" <frank at compostlab.com>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>
Sent: Monday, December 06, 2010 2:01 PM
Subject: Re: [Stoves] Drawing down the dung pile
Stovers,
I have washed a lot of dung and compost. We like to have it clean : )
When doing weed seed testing we wash out all the salts and soluble
organics that, if remained, can make the mix go anaerobic. We wash until
the electrical conductivity is less than 1 mmhos/cm. Then place the mud
on a bed of sand to let drain and air both above and below. Then add
seeds to one corner to make sure if there were weed seeds they have the
conditions to grow.
# It is the soluble salts and organics that are teh most valuable agricultural nutrients. I am guessing that teh soluble organics would have a tendancy to hold water and slow the natural drying of dung. Removing them from teh remaining fiber should allow easier drying. Washing to give a conductivity of less than 1 mmhos/cm would certainly be necessary in a repeatable test, but such repeatable results may not be required when the end product is intended for fuel.
The washing is done by the following: Place dung in a five gallon
bucket., fill with water and mix. Prepare a smaller plastic bucket by
cutting out the bottom , duct tape a fine mesh screen over the bottom.
With up-N-down motion move the smaller bucked down through the muddy
water. The up-N-down keeps the screen clean. The water that goes into
the small bucket is removed by a smaller bucket until as much of the
water as possible is removed. Then repeat the process until the water is
clear or the EC is below one mmhos/cm.
# This sounds like a very good basic process.Cheap and simple.
----- Original Message -----
From: <psanders at ilstu.edu>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>; "Crispin Pemberton-Pigott" <crispinpigott at gmail.com>
Cc: <wastemin1 at verizon.net>; "Stoves" <stoves at lists.bioenergylists.org>
Sent: Monday, December 06, 2010 6:26 PM
Subject: Re: [Stoves] Drawing down the dung pile
> Dear Crispin, Kevin, Frank and all,
>
> I have read the later responses, and I like the "washing", but only if
> it is clearly shown that a type of dung (each type to be considered
> separately) does emit "bad stuff" if not washed. Or wash it if
> nutient value for plants is shown to make it worthwhile.
# I don't have specific references to investigations showing that "dung fuel is hazardous", but I do know that combustion of organic materials containing chl;orides will produce dioxins. I have seen somewhere that there is a high incidence of blindness among elderly Indian Women who have tended dung fires. Manure tea is well known for its advantages to agriculture.
>
> Otherwise, the extra work (and water that might not be plentiful)
> could make dung fuel to be too much trouble to be well utilized widely.
# Good point. There must be clear and palpable benefits from teh extra effort required to wash the dung. Such benefits could include:
1: Better burning fuel
2: valuable fertilizer benefit
3: Cleaner and more acceptable fuel, less liable to harbour insects and pests, easier to handle, etc.
4: Health benefit
5: Higher calorific value per pound or kg of fuel, due to higher lignin content.
6: Others?
>
> Washed or not, I like dung fuel, have used it a little in India, and
> would like to be part of the team.
# It seems a shame to burn the fertilizer components of manure.
>
> In case you couldn't guess, my interest is in using dung fuel in TLUDs
> (of various designs). Because TLUDs need "chunky dry biomass", I
> will work on having appropriate sizes. Here are some initial thoughts:
>
> 1. Llama dung is the right size, as is the size from sheep and some
> other animals. "Correct size" dung should not be washed (unless shown
> to be with undesirable emissions. And that refers to the emissions
> from TLUDs that have great abilities for nearly eliminating CO and PM.
> But does the other "bad stuff" get through the TLUD fire? Not yet
> studied, as far as I know.
# A major objection to Municipal Solid Waste Incinerators comes from tehir production of dioxins. This is well documented. Dioxins can be removed from such gas streams, but a special "dioxin capture system" is required. If TLUD's burn a fuel containing chlorides, tehy will definitely produce dioxins, and if teh TLUD's do not have a dioxin capture system, they will indeed be releasing dioxins.
>
> 2. Llamas have the nice habit of pooping in just a few locations.
> Easy to collect it. And it is already in use widely in the high Andes
> mountains area. And llamas as "luxury animals" or pets or for fine
> hair fibers are now found in the Affluent societies, so there is
> moderate access to the dung for experimental purposes.
# Certainly, this behaviour pattern can be used to great advantage. However, to eliminate the dioxin concern, teh well shaped llama and sheep poo would have to be washed, and in tgeh process, this initial shape advanyage would be lost.
>
> 3. For TLUDs. in India we made dung tablets. Could work also with
> washed dung, maybe even better if washed. And it can be mixed with
> sawdust or rice husks or other small-particle biomass that could even
> be wet/green because the tablets need to be dried. The dung (or
> mixture) is spread out on a firm flat surface (board, cement, asphalt,
> whatever) about 1 to 3 cm thick. While wet, it is "scored" or
> imprinted with the edge of a piece of metal (like a license plate) or
> wood form. The imprints are parallel and about 3 to 6 cm apart, and
> then again imprinted perpendicular to the first lines. When the dung
> is dry, the tablets hang together in pieces with 4 to 8 tablets
> together. Can be turned with a spatula (a large one) for drying on
> the bottom. When fully dried, they are placed into bags or boxes.
> the user finishes breaking them into the individual tablets when
> placing the fuel into the TLUD (or other stove.).
# As mentioned initially, teh washing process may remove natural binder substances, and replacement binders may be required.
>
> So, let's have an outline of a plan of actions. Do it on the Stoves
> Listserv in case we can attract a few more participants.
>
> Paul "Dr. TLUD"
> Proud to be working with "Captain Dung" or what was Kevin's name?
Aheeem... "Dr. Dung." ;-) This is in addition to my other titles of "Dr Poo", where I fixed a sewage treatment plant, and "Dr. Slime" where I showed a friend how to eliminate slime from her fish pond.
>
----- Original Message -----
From: <ajheggie at gmail.com>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>
Sent: Monday, December 06, 2010 6:42 PM
Subject: Re: [Stoves] Drawing down the dung pile
> On Monday 06 December 2010 17:22:14 Kevin wrote:
>
>>
>> Years and years ago, I started a thread about using dung fuels and
>> interest in it was very conspicuous by its absence.
>
> The my first swirl stove which I demonstrated to Ronal when he was here in
> 2002 was fabricated in order to burn dung, I had a snappy name for
> it ;-). Horse dung is a problem here because the small fields used
> for "horseyculture" become horse sick from overgrazing and stabled horses
> produce dunged bedding which the owners are not in a position to deal
> with. Often because they are bedded on woodflakes the stable owners burn
> the heap in a smouldering mass with a characteristic sickly sweet smell.
> One of the reasons I looked at the problem was because heavy stocking led
> to parasitic worm infestations, some of the anthelmic treatments also
> killed earth worms. So some owners would even collect the dung from the
> fields.
>
# Reduction of such disease and parasite problems could be another benefit to clooecting dung, and washing it for fuel. However, this might concentrate teh problem. On teh other hand, if the pathogens "stayed with the washed dung", then they would end up being disposed of by burning
>
>
>> From what I can
>> understand, dung fuels are about the worst possible fuel, "as is",
>> because of moisture and chlorides. Moisture makes for difficult
>> burning,
>
> Yes often over the 80 odd % that means the energy needed to volatilise the
> moisture exceeds the heat available in the fuel.
# If the dung is sun dried before being burned, teh problem will be significantly lessened
>
>
>> and chlorides make dioxins.
>
> I agree dioxins must have chlorine but I thought the route was via the
> break down of an organic chloride rather than the dissociation of an
> mineral chloride.
# No. Dioxins are formed at the "tail end of the combustion process", when the liberated chlorides, from either organic or inorganic sources, recombine with products of incomplete production.
>
>
>> I advocated washing the dung, to extract the solubles, and then using
>> the water extract as a liquid fertilizer. Then dry the residue, for use
>> as a fuel. It should then be a superior fuel to wood, in that it would
>> have a higher percentage of lignin, which has a higher heating value
>> per pound than cellulostic biomass.
>
>
> Even better if the dung has been through an anaerobic process first, then
> all the volatile solids are gone, the soluble minerals are in the "tea"
> but how to separate the solid from the tea, drying is no good as this
> would leave the minerals in the dried sludge. A farmer friend of mine
> with an anaerobic digester for his dairy herd has a separator but I have
> no idea how it works, the output still looks pretty wet.
# Anaerobic digestion will, of course, yield methane as a fuel. The discharge from such a digester has all teh mineral nutrients, and all the lignin from the animal feed. However, it is a problem operating a thermophyllic or mesophyllic digester in cold climate situations. Frank's method (above) or some variant, could seperate out the liquid from teh anaerobic sludge, for direct field application.
>>
>> Leaching the solubles from the "raw dung" should remove the chlorides,
>> and should virtually eliminate the creation of dioxins, while at the
>> same time, produce an excellent fertilizer solution, containing Ca, P,
>> K, and organics beneficial to plant growth.... hormones, proteins, and
>> nitrogen compounds.
>
> Yes this is what I would hope for.
Yes, it does work, as evidenced by teh success of those using "manure tea."
----- Original Message -----
From: "frank" <frank at compostlab.com>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>
Cc: <wastemin1 at verizon.net>
Sent: Monday, December 06, 2010 7:07 PM
Subject: Re: [Stoves] Drawing down the dung pile
> Paul and all,
>
> When washing dung most disappears in the wash water. So you are left
> with a fraction of what you started with and a lot of anaerobic solution
> that will need aeration to stable before a lot can be applied.
# Since manure is applied directly to soil without an aerobic treatment, why couldn't the manure tea be directly applied without aeration?
>
> The minerals in dung (not washed) will convert to carbonate (CaCO3,
> NaCO3 etc) form so there will be more liming of the soil if the salts
> are not washed out (I think this is what happens). This not necessarily
> a bad thing. If heated higher it may go to oxides. The oxides are more
> of a problem because there is no buffering to keep the pH from going too
> high when applied in high amounts.
# I would think that the main soluble minerals in dung would be sodium and potassium chlorides. There may be a danger in very dry areas of sodium buildup in the soils.
>
> The more minerals may cause more deposit in the stove as a crust. Has
> this been seen in our small stoves? I have ashed a lot of organic
> biomass material at 550 deg C and found a very small fraction of samples
> form more than an ash that is easily removed from the container.
I don't know enough about teh mineral constituents of dungs. Burning tests using teh washed dung would quickly show if ash was a concern.
----- Original Message -----
From: Anand Karve
To: Discussion of biomass cooking stoves
Sent: Monday, December 06, 2010 11:32 PM
Subject: Re: [Stoves] Drawing down the dung pile
Dear Crispin,
dung cakes are regularly used as fuel even in India. In areas where the rainfall is scanty, and there are no trees, dung is used as the main cooking fuel. In the high Himalaya, above the tree line, yak dung is the only fuel available to the locals. The ash content of dung is normally very high. In the case of animals eating mainly grass, the ash would consist mainly of silica. I have heard of a of filter press, which can remove the water from the dung along with the dissolved minerals. This would leave a product with a higher calorific value. It can be briquetted and sold as a standard fuel.
# While the ash content might be high, that would only be a concern if it caused slagging. Washing teh dung would remove teh soluble minerals, which usually act as fluxes, lowering the ash melting temperature.
Yours
A.D.Karve
----- Original Message -----
From: Richard Stanley
To: Discussion of biomass cooking stoves
Sent: Tuesday, December 07, 2010 12:21 AM
Subject: Re: [Stoves] Drawing down the dung pile
AD, Crispin, Frank, Kevin and all others concerned with dung briquettes,
While in Arusha Tanzania recently, I discovered that one of the lead briquette trainers in Kenya, Francis Kavita, has been teaching the Masaai how to make co dung briquettes for the past several months. Your insights, Kevin and frank about carcinogens/ chloride blindness etc are intersting and I have duely passed them on to Francis.
As to dilution of nasty compounds the normal wet low pressure briquetting process uses water--- but rarely is anything wasted in the process. The water expelled for the cylinder on compression, is recycled as well.
# OK! Such recycling of teh "wash water" or "manure tea" would give a tea of higher concentration, and this could be advantageous in areas where water is scarce.
However the practice of washing away unwanted elements is common to briquetters as it is to conventional washing of seeds, beans cassava and other plant material in traditional food preparation. In briquetting, certain carcinogenic and foul smelling glues in certain types of cartonboard are diluted nad washed off this way. There is no real reason that the same technique could be applied for preparing "clean cow dung" as well.
Will revert back to the group with what Francis says about all this..when he next finds a nearby internet cafe with electricity or at least petrol for their generator.
# Yes, it would be helpful to have his feedback.
Thanks again though for the insights.
Richard Stanley
Best wishes,
Kevin Chisholm, aka "Dr. Dung."
>
From: stoves-bounces at lists.bioenergylists.org [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Kevin
Sent: 07 December 2010 01:22
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Drawing down the dung pile
Dear Crispin
Years and years ago, I started a thread about using dung fuels and interest in it was very conspicuous by its absence. From what I can understand, dung fuels are about the worst possible fuel, "as is", because of moisture and chlorides. Moisture makes for difficult burning, and chlorides make dioxins. Also, the very people who are so desperate as to need to burn dung for fuels are usually the same people who are equivalently desperate for fertilizer. I understand also that blindness is very common with Indian Women who have been using dung fuels.
I advocated washing the dung, to extract the solubles, and then using the water extract as a liquid fertilizer. Then dry the residue, for use as a fuel. It should then be a superior fuel to wood, in that it would have a higher percentage of lignin, which has a higher heating value per pound than cellulostic biomass.
Leaching the solubles from the "raw dung" should remove the chlorides, and should virtually eliminate the creation of dioxins, while at the same time, produce an excellent fertilizer solution, containing Ca, P, K, and organics beneficial to plant growth.... hormones, proteins, and nitrogen compounds.
I'd be glad to work with you, in developing a "dung washing system.". I think it could help with both fuel and fertilizer needs
Best wishes,
Kevin Chisholm, aka "Doctor Dung." :-)
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