[Stoves] LPG import in India

[Andrew Heggie]

On 29 December 2017 at 02:31, Crispin Pemberton-Pigott
<crispinpigott at outlook.com> wrote:
> Dear Andrew
>
> Re the Benzo(A)pyrene
>
> Do you recall that last year I was working with James Robinson at SNV in Ghana? We produced a fish smoker that reduced the BaP dramatically (97%) by changing the temperature of processing.

Yes I do remember your mention of it.

>
> It is in the meat. But is it in the vegetables? We demonstrated that it is produced by overheating the fish oil, and is not from the smoke. I think most foodie people believe it is from the wood. It seems to be almost entirely from the heating of the food.

I don't know the route to PAH and it might just be that the
triglycerides offer a better species source of PAH. I also don't know
why benzo[a]pyrene is selected as an indicator for PAHs in general,
there seems to be some debate as to whether it is the most noxious.
What seems beyond doubt is that is is formed as a product of
incomplete combustion (partial oxidation) of any organic compounds as
well as diesel or coal. It is also formed at above 400C and that is
the region where we see some interesting changes from aliphatic
(chainlike compounds like cellulose) to phenolic ones containing
complete carbon rings. If you look at the structure of cellulose you
will see it only needs the substitution of an oxygen atom by a carbon
one to complete a benzene ring. One of the ways graphite is formed is
to take an organic compound, form a shape and then heat it to
progressively to remove oxygen and hydrogen until at around 3000C all
the carbon atoms form carbon rings in a stack of graphene sheets.
>
> High oil fish dried traditionally or in the FAO promoted 'improved smokers' have very high BaP‎ and the non-oily fish do not. Same fuel.

It makes sense that it is the oil then, note also flame grilled meats
are high in PAHs.
>
> Has anyone measured BaP in smoke? Philip, maybe?

I don't have any means of measuring it but woodsmoke (maybe from
wildfires) is widely reported as a major source, presumably good
secondary combustion prevents their formation  but would cold smoking
do also?. We do know it's significance in sump oil and coal smoke as
it is implicated in two cancers which became early reported industrial
diseases, scrotum cancer in young chimney sweeps and young auto
mechanics.

Andrew