[Stoves] Heat destroys Jatropha toxins Re: jatropha, stoves, and biochar.

[Crispin Pemberton-Pigott]

Dear Jatropha Planters and Burners

 

This is a response from David House, he of biogas fame. Fortunately we
overlap on a different environmental list.

 

From: David [mailto:david at h4c.org] 

On 1/26/2011 6:39 PM, Crispin Pemberton-Pigott wrote: 

Dear David

There is a big discussion going on at the stoves list (bioenergylists.org)
about burning jatropha seeds or seed cake.
If it is burned, is there any risk of creating dangerous fumes?
If it is pressed first then burned?
If it digested, then burned?

Honestly I don't know of any references to determine whether any of the
options listed might be harmful. I do know that burning the glycerol which
results from transesterification can produce poisonous fumes (acrolein), but
never investigated burning the seed cake-- I was hired for example by one
client to find out if it would digest, and it does, easily. (I am attaching
the report herewith.) (At the same time, it would not make sense to burn it
after digestion-- it would be too wet.)

As well, with regard to composting the seed cake and using that as
fertilizer, I would feel quite satisfied-- even though in this case as well,
I cannot provide a peer-reviewed source-- in saying that it will not harm
the soil. 

After all, whatever is composed, decomposes. What poisons the soil is either
elemental-- too much copper, for example, can harm plants-- or it is
biologically recalcitrant. Now, what is recalcitrant often depends on what
is in the soil. Some substances (particularly man-made ones), nearly
regardless of where they end up under the surface from the arctic to the
equator, are recalcitrant; but with others, a great deal depends on what is
available in the soil that can make some sort of feast of it. If the soil is
dead, then it is much easier for something toxic yet decomposable to
accumulate, and after all, something was probably put on the soil to kill
it-- likely chemical ag of some sort. Build up of some toxic-yet-degradable
substance would simply be another side effect of the main problem.

Ecologically speaking, some plants build toxicity to their own seedlings in
the soil below them. Peach trees, if memory serves, have this effect, and as
such peach trees will never form a climax forest. But that is not toxicity
in any general sense. I have read a lot of reports about Jatropha, and there
is enormous literature about co-plantings of this and that with Jatropha,
because the bush/tree takes 5-8 years to get established, so people have
done all sorts of things to make the land productive by planting between the
rows, both early on, and later even in mature stands. In all the reports I
have seen about co-plantings, I have never seen any mention of toxicity.
Now, this is a sort of negative evidence, in two senses. First, I am not an
expert, just an interested amateur. No doubt there is a vast literature
which I have never seen. And second, obviously, absence of evidence is not
evidence of absence. Even so, I would think that if Jatropha in fact poisons
the soil, then it would be relatively common knowledge, and at least a few
of those articles would have said "Don't plant X with Jatropha. It dies." 

To return to the question of toxicity when burning, I would think that an
enormously complex set of chemicals would be released from any combustion,
unless done under conditions that would guarantee that all parts of every
particle of the seed cake were exposed to the same conditions of heat and
sufficient oxygen. They won't be. So my assumption would be that whatever is
toxic in Jatropha when eaten would be present in the smoke, along with a
whole alphabet soup of other substances. WHO says 1.6 million die each year
from smoke inhalation and related causes, and surely most of what's burned
is harmless cellulose and lignin and all those other innocents. I can't see
that adding poison oak to the fire is likely to result in smoke that is less
dangerous-- there is literature available about that bad idea-- and the same
would sensibly be true of Jatropha seed cake. It's got bad stuff for mammals
in it if they eat it, so surely some of that would show up in the smoke and
would offer its measure of harm when the smoke inhaled. 

But again, for the most part that's just me gibbering, and not reel scienze.
-- 

David William House

"The Complete Biogas Handbook" www.completebiogas.com
Vahid Biogas, an alternative energy consultancy www.vahidbiogas.com

"Make no search for water. But find thirst,
And water from the very ground will burst." 

(Rumi, a Persian mystic poet, quoted in Delight of Hearts, p. 77)

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