[Digestion] plastic

Thu Aug 24 07:41:59 CDT 2006

Joshua, Hi

To add my comments to Paul's:

Black plastic is probably better than clear plastic for biogas. The 
literature suggests that methanogenic bacteria dislike light as well as 
oxygen. I must admit, I have not tested that, but most slurries are a dark 
brown color, which would not let light get much below the surface, anyway.

I agree that long and skinny is good. If you are short of space, you can 
use several tubes side-by-side and connect them in either series or 
parallel. Series connection is probably better. Your main problem is to 
make sure all the connections are gas and water tight.

In my Nepal days (see my book below), we did make a Chinese design ceramic 
gas light. I did find a cross-sectional drawing and I will send a copy to 
Paul to make available (we are not supposed to put attachments in these 
e-mails to the discussion group).

The following description will make more sense, once you can see the picture.

We made the mixing tube from a good quality clay, with the help of moulds, 
which was then fired. The valve and needle assembly were made from brass. 
The numbers are mainly dimensions in mm. The body fits into a reflector, 
with a glass bowl underneath to protect the flame. The parts that stick out 
from the outside of the mixing tube are designed to fit into clamps 
attached to the reflector. I think we "borrowed" the reflector and glass 
surround from lamps we purchased from India.

Gas lamps were always a problem, because they were rather unreliable. 
People needed a steady supply of the mantles (they were the same as used in 
petromax lamps) and insects kept getting in the small holes and blocking them.

David

D.J. Fulford "Running a biogas Programme: A handbook"
Published by Intermediate Technology Development Group, London (1988)
ISBN 0 946688 49 4
http://www.developmentbookshop.com/detail.aspx?ID=491

At 09:01 24/08/2006 +0930, Paul Harris wrote:
>G'day Joshua,
>
>I agree with your applications for biogas!
>
>Black plastic will be fine (most large digesters are
>steel/concrete/fibreglass!) - you may get a benefit as photosynthetic
>bacteria/algae won't be able to produce oxygen (I'm an engineer, not a
>biologist) but on the down side photosynthetic sulphur bacteria won't be
>able to break down H2S (but that's minor!).
>
>Long and skinny is fine (better plug flow) but it is the total volume
>(compared to the input volume to give retention time) that is critical.
>I can send you an excel model for you to have a try with if you like.
>
>I would also be interested in any information about gas lighting.
>
>Happy digesting,
>HOOROO
>
>Joshua Bogart wrote:
> >
> > I am working on a project putting in small biodigestors to be used with
> > household and livestock waste to provide cooking and possible lighting in
> > rural honduras. I have three questions, and please forgive me I am an
> > ecologist not an engineer
> >
> > 1)We have not been able to locate suitable clear plastic here in Honduras
> > but we ahve been able to locate black plastic tubes of suitable dimensions.
> > I can't see that there should be a difference between the clear and dark
> > plastic as we are not using a photosynthetic process. but can anyone 
> tell me
> > otherwise.
> > 2) The systems I have seen here have a diameter of 2 meters and a lenght of
> > 10 meters which gives them a volume of 31.41 cubic meters. the plastic we
> > are thinking about we caon only find in tubes of 90 cm which gives at ten
> > meters long a volumn of 6.36 cubic meters. in my original readingthe length
> > ahs more to do with retention time and killing off all possible pathogenic
> > organisms , I was wondering how much this difference in volumn would affect
> > methand output.
> >
> > the third question has to do with using low presure mehtane for these
> > digestors to burn in lamps I have read of some designs in the chinese 
> biogas
> > manual using clay bodies I was wondering if anyone knows of a simple design
> > to make this type of lamp. I am interested in the diameter of the gas
> > entrance and size of the air mixing chamber.
> >
> > thank you very much
> > --
> > Joshua D Bogart
> > Apartado postal Numero 3
> > Guaimaca, FM Honduras, CA
> > cellular 967-8187
> > _______________________________________________
> > Digestion mailing list
> > Digestion at listserv.repp.org
> > http://listserv.repp.org/mailman/listinfo/digestion_listserv.repp.org
>
>--
>Mr. Paul Harris
>Faculty of Sciences, DP710
>The  University of Adelaide, Roseworthy Campus, AUSTRALIA 5371
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*** Dr David Fulford, MSc Renewable Energy, Engineering Building ***
***     School of Construction Management and Engineering        ***
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