[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 

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 

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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