[Stoves] Drawing down the dung pile

[ajheggie at gmail.com]

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.




> 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.


> 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.


> 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.
>
> 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.

AJH