[Stoves] Dung tablet data

[Paul S. Anderson]

Hello, especially to AD Karve,

Here in Sanghi Nagar, India, I have experimented with dung fuel.  For use in a
TLUD gasifier, I have made square dung tablets about 5 to 8 mm thick, and 20 to
30 mm on each side.

The dung is worked (manually by 2 ladies with experience)for consistency like a
very thick paste.  We can add any small-particle biomass such as sawdust or
rice husks at this time.  Then the mass is spread out on flat surfaces at the
desired thickness, and we use the edge of a piece of metal to press in the
horizontal divisions and then the vertical divisions.  Let it dry for a couple
of days in the hot sun.  The tablets cling together in groups of 4 to 20, and
are easily broken apart into single pellets, with surprisingly little dust or
powder evident.  They store nicely.  No smell is associated with the dry dung
tablets.

The tablets are loaded into the TLUD gasifiers by scoops or handfuls.  Very
clean.  They are pyrolyzed nicely and do yield considerable ash (not quantified
at this time).

Now some questions:

1.  How much energy content is lost while the fresh dung lays on the ground for
hours or days or weeks?

2.  Is the work to add other biomass worth the effort in terms of energy output?
 To take moist fresh dung and spread it with a shovel and mark it ainto tablets
seems easy compared to the mixing of it by hand.  In the traditional dung
processing, the ladies generally mix in straw and make paddies or thin cakes. 
The straw is a bio-fuel, but its main purpose (I believe) is to hold the paddy
together, especially while it is drying on the outside wall of a building.

Note:  In the tablets, we do not want to use any straw or stringy stuff because
that can be linking two or more tablets and make it hard to separate them.  We
did not like the result with mixed-in wood shavings, so straw would be even
worse.  But sawdust and rice husks worked very very well.  But I am not sure
the mixing is worth the effort.

3.  Most of the mineral nutrients remain behind in the ash or char plus ash. 
So, what reduction of fertility benefits is there from spreading that ash
versus spreading natural dung as manure in the fields?

4.  I believe AD told us that dung as combustion fuel yields about 4 times the
energy that comes from the same dung used as biodigestor fuel to create biogas.
 Did I say that correctly?  And when micro-gasifiers become popular, what will
be the role of dung as a binder or as 100% dung fuel or for biogas?

I will try to put together a small PowerPoint show about the dung tablets for
ETHOS

Paul
-- 
Paul S. Anderson, Ph.D., Geography professor - Emeritus
Telephone:  USA-309-452-7072 (residence and office)
Internet site:  www.ilstu.edu/~psanders
For my gasifier stoves info, go to:
http://bioenergylists.org/contributors#Paul_Anderson





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