[Gasification] Biochar et al.
David Murphy
djfmurphy at dodo.com.au
Fri Dec 6 16:00:16 CST 2013
Greetings Biochar/Gasifier people !
Everybody & his dog seems to have something to say
about charcoal/biochar/biochar-compost mix and so
on. Well, here's another dog to bark his piece !
Biochar is often seen as the great agricultural
panacea, but _it is not_.Biochar is a name given
to plain ordinary charcoal to indicate that it is
destined for use in soil improvement, but
basically it is still plain ordinary charcoal,
just crushed into smaller particles. In some
circumstances it is a very beneficial tool but it
is not magical as some proponents seem to think.
Just remember, all charcoal has a bio-origin - wood.
In some Ag. trials in Australiait significantly
improved crop volume (treble in one case) but in
other instances, nothing worth writing home
about.It depends on what the soil is like to start
with.
Charcoal is stable.That means it does not take
part in any composting system (which is one
primarily of bacterial digestion) and it is
indigestible so that when offered as a dietary
supplement (in poultry food for example) it passes
through the digestive system physically unchanged
but will adsorb a high proportion of the gases and
some toxins produced in the process of digestion,
because that is what charcoal does. For this
reason, it's adsorption capability, poultry will
generally do better on a little charcoal.
Quite a few pages could be filled on the
beneficial services provided by charcoal as it
travels through the digestive system, but it does
it as charcoal only and as nothing else. By all
means use a little in the feed, you can only benefit.
The only physical way to change the nature of
charcoal is to burn it. That is why it lasts in
soil (or wherever it is) for thousands of years.
It has an incredibly high surface area of 360 m^2
(varies) and is a mass of minute tunnels which in
turn means a very high volume and gases become
trapped in these tunnels.It does not _ab_sorb, it
_ad_sorbs and traps only.The difference between
absorb and adsorb is the same as the difference in
liquids of suspension and solution.Clay particles
will be in suspension, sugar and salt go into
solution.
Charcoal is useful in an aerobic composting system
because again of the entrapment of air in the
tunnels.A composting system goes well if there is
enough oxygen bearing air available to the
bacteria which are a significant part of the
system.The more air, the higher the population of
bacteria (other factors being OK). The charcoal
itself is inoperative, and doesn't change, nor is
it a catalyst, it simply provides a service. It
will only provide a haven for soil benevolent
bacteria if there is something trapped in the
tunnels which the bacteria can eat.
Charcoal is a good adsorber of gas and liquid
simply because that is what it does.Zeolite on the
other hand, can have an even higher surface are
per gram and has a propensity to entrap gases,
most particularly nitrogen in it's various forms
-- as gas -- ammonium for example -- and in
liquids as a salt of NO_3 .It actually draws them
in (like a magnet attracts ferric objects) where
charcoal just takes it as it comes. It is easy
to see also why charcoal is so effective as a
filter, but if you have a solution rich in
nitrogen, run it through Zeolite and the N will be
removed. Add some to the litterin poultry grower
sheds, there will be fewer mortalities because the
ammonia which sometimes will asphixiate small
birds will be absorbed. Zeolite will take N out
of solution, charcoal will not. There's 40
natural forms of Zeolite and more than another 150
can be synthesised, so choose carefully for the
one most appropriate to your problem. Zeolite
can perform an amazing range of actions. Once
used and applied as fertiliser, Zeolite
subsequently will release the Nslowly and remain
in the soil as a balancer of N. Too much, it will
take it in (so that the soil pH is not lowered)
and release it as required.
Charcoal's great stuff though, it's easy to make
and holds answers to a lot of problems - but not all !
David Murphy.
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