[Stoves] Spherical Cow Dung Balls for ND-TLUDs in Bangladesh : Washed Dung not Successful

[Julien Winter]

Hi all;

I just got some feedback from Bangladesh on dung-washing.  So far, the
results are not so positive.  As one would expect, if sloppy dung is
washed, there is almost no fiber left to make fuel.   If dung that fell as
balls is used, then there is a fibrous mass left after washing, but it is
no longer sticky, and it is not good for mixing with sawdust for fuel to
make firm fuel balls.

I mentioned before that cow manure is very variable, depending greatly on
what they eat.  If cows are fed green forage, than has very little fiber,
then manure will be loose.  If fact, North American beef cattle when fed
large amount of grain in their diet function more like a mono-gastric pig
than a ruminant.   On these kinds of diets there no fiber to collect after
digestion.

Foraging cattle eating straw and other coarse vegetation will pass a lot of
undigested fiber in their manure.  But is would seem that after it is
washed, it is not sufficiently sticky to make fuel balls with sawdust.

Another aspect of this is that manure is usually collected in piles.  Under
those conditions it will continue to decompose, or compost.  If the pile is
oxygenated, lignolytic fungi will release enzymes that break down the
fibers.

All this being said, Mahbubul Islam and co. are still working on different
methods to make fuel balls.  The burning characteristics of the dung is
much improved by co-firing with biomass  (1:1 by volume).   Mahbubul
mentioned that the physical structure of the fuel bed in a TLUD is much
better with small balls than with odd-shaped chunks of wood, so the flaming
pyrolysis reaction is more uniform with balls than wood pieces.  If balls
were tested in a TLUD under a hood, we could likely find that emissions are
cleanest with the dung-biomass balls.

Cheers,
Julien.

-- 
Julien Winter
Cobourg, ON, CANADA
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