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<DIV><FONT face=Arial size=2>Yvonne Hi again! When you talk of
security, I would think that the greatest danger would be from
asphyxiation. I don't see explosions as being a great danger. When
you crack open a digester, Methane is lighter than air and will quickly
rise up out of the way. But Carbon dioxide is much heavier than air
and will stay down in the box. if it is dug into the
ground. The cheapest system is to dig a trench in the ground
with one end sloping upwards to make a ramp that you can run a wheel barrow down
into the trench.. The sides are plastered ferrocemento style, like
throwing cow dung onto the sideof a wall to dry. The top cover is made from
PVC tarpaulin material and it is sealed into the ferrocemento sides by
being pinned down into a small narrow trench made of cement and integral with
the sides.</FONT></DIV>
<DIV><FONT face=Arial size=2>Then the sealing trench is filled with water
or better still a clay slurry. However, the real danger
is CO2 remaining down in the digester and I would not recommend
blowing it out with Jamies idea of a car exhaust either. CO2 is so
sneaky inthat you can't really smell anything an two good breathes of CO2 and
you will be dizzy enough to fall down. Then you are really in trouble. One
to two minutes and you are a goner!
</FONT></DIV>
<DIV><FONT face=Arial size=2> If security/safety is your main concern
then it takes two sheets of nylon reinforced PVC tarp. You lay
one down on the ground as a base, with the edges turned up, and you
pour a concrete floor over the tarp, strong enough to support Men Wheelbarrows
Tractors or whatever. Then you heap up your digestable material on the
floor and then pull a top cover of PVC tarp over the top and seal it
to the edges protruding from underneath the floor. That seal is made from
sliced up Polythylene pipe and does not require water. Rather its a couple
of tubes of lubricating grease every time you seal up a new batch of
material. </FONT></DIV>
<DIV><FONT face=Arial size=2>Being built on level ground the biogas goes upwards
and the CO2 fraction spreads out over the ground and may kill a few low lying
animals but not people or their dogs. </FONT></DIV>
<DIV><FONT face=Arial size=2>Because the digester is so flexible it can be
sucked virtually dry of biogas and the top will be sucked down on top of the
substrate material. Then very very little gas will be wasted.
</FONT></DIV>
<DIV><FONT face=Arial size=2>If you were not so worried about explosions, I
would be suggesting that one of those 12 volt blowers used to pump up your
air mattress for camping out, or your swimming/paddling pool would do all
the blowing and sucking that you would want. In actual fact, with no
air leaking in you can suck out pure biogas with no danger at all.
It takes a 15% mixture of gas in air to make an explosion.
However, even so, it would be wise to choose a blower that doesn't spark at
the brushes.</FONT></DIV>
<DIV><FONT face=Arial size=2>Home me in a bit further on your vision and I
will come back with more details of which ever way you want to go.
Ken C. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial size=2> </FONT>----- Original Me</DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial"> </DIV>
<DIV style="FONT: 10pt arial">ssage ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=Yvonne.Voegeli@eawag.ch
href="mailto:Yvonne.Voegeli@eawag.ch">Voegeli, Yvonne</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=digestion@lists.bioenergylists.org
href="mailto:digestion@lists.bioenergylists.org">For Discussion of Anaerobic
Digestion</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, October 29, 2010 10:06
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Digestion] Dry fermentation
in developing countries</DIV>
<DIV><BR></DIV>
<DIV class=Section1>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Dear
all,<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Thank you very much
for your feedback and ideas. We will have to think more about David’s’
suggestion using two flame traps.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Ken is right; I
should have given a bit more details on the project. I have to admit that we
are at the very beginning... The project is located in Kumasi, Ghana, and our
local research partner is the KNUST University of Science and Technology. The
pilot plant shall be located at the university campus and the feeding material
will consist of organic household waste or food waste from restaurants. In a
first step, two Swiss students will work on the project for 6 months (start in
December), spending 4 months on site. Their task is to identify the suitable
material, that’s why I can’t give you the details on what exactly is
available. At first, I was also thinking about a shipping container (what
about corrosion?), but cement materials are also available as well as skilled
workers. We will have to compare the different options and
costs.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">On principle, the
idea is that such a plant would be operated by the municipality or a private
contractor (not by farmers), as our focus is on municipal solid waste. There
are still many open questions, but my biggest concern was the security - if it
is possible at all to construct a simple digester which is
safe...<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">I think the students
might contact some of you directly for further questions later
on.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Thank
you,<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Yvonne<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"> <o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<DIV>
<DIV class=MsoNormal style="TEXT-ALIGN: center" align=center><FONT
face="Times New Roman" size=3><SPAN style="FONT-SIZE: 12pt">
<HR tabIndex=-1 align=center width="100%" SIZE=2>
</SPAN></FONT></DIV>
<P class=MsoNormal><B><FONT face=Tahoma size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">From:</SPAN></FONT></B><FONT
face=Tahoma size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">
digestion-bounces@lists.bioenergylists.org
[mailto:digestion-bounces@lists.bioenergylists.org] <B><SPAN
style="FONT-WEIGHT: bold">On Behalf Of </SPAN></B>Ken Calvert<BR><B><SPAN
style="FONT-WEIGHT: bold">Sent:</SPAN></B> Freitag, 29. Oktober 2010
09:48<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> For Discussion of
Anaerobic Digestion<BR><B><SPAN style="FONT-WEIGHT: bold">Subject:</SPAN></B>
Re: [Digestion] Dry fermentation in developing
countries</SPAN></FONT><o:p></o:p></P></DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> Yvonne Hi! When you
say developing countries, what sort of construction materials are you
thinking of? Would old 20 tonne shipping containers be
available?</SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Are cement
materias and tradesmen skilled in cement plaster work readily
available? What about PVC tarpaulin cloth? Are there
trucks on the roads that have waterproof covers that can be strapped
down over a load? What is the local soil and
terrain? Is it possible to dig say 2-3 metres deep in the
soil and get a smooth surface, or is the terrain too soft and sandy
to hold to the shape of a cistern or trench dug in the soil?
Is it too rocky to allow any sort of digging at all? If you can home in
a little more on the country side and local
skills available I can make several different
suggestions. Sincerely, Ken Calvert. <A
href="http://www.coffee.20m.com">www.coffee.20m.com</A></SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> </SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> </SPAN></FONT><o:p></o:p></P></DIV>
<BLOCKQUOTE
style="BORDER-RIGHT: medium none; PADDING-RIGHT: 0cm; BORDER-TOP: medium none; PADDING-LEFT: 4pt; PADDING-BOTTOM: 0cm; MARGIN: 5pt 0cm 5pt 3.75pt; BORDER-LEFT: black 1.5pt solid; PADDING-TOP: 0cm; BORDER-BOTTOM: medium none">
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">----- Original Message -----
<o:p></o:p></SPAN></FONT></P></DIV>
<DIV style="font-color: black">
<P class=MsoNormal style="BACKGROUND: #e4e4e4"><B><FONT face=Arial
size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Arial">From:</SPAN></FONT></B><FONT
face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> <A
title=Yvonne.Voegeli@eawag.ch href="mailto:Yvonne.Voegeli@eawag.ch">Voegeli,
Yvonne</A> <o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><B><FONT face=Arial size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Arial">To:</SPAN></FONT></B><FONT
face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> <A
title=digestion@lists.bioenergylists.org
href="mailto:digestion@lists.bioenergylists.org">digestion@lists.bioenergylists.org</A>
<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><B><FONT face=Arial size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Arial">Sent:</SPAN></FONT></B><FONT
face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">
Thursday, October 28, 2010 9:53 PM<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><B><FONT face=Arial size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Arial">Subject:</SPAN></FONT></B><FONT
face=Arial size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">
[Digestion] Dry fermentation in developing
countries<o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P></DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Dear
all,<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">I like to start a new discussion
on a different topic, namely the dry-fermentation process (discontinuous)
similar to the digesters developed by the companies Bekon or Bioferm in
Germany. The organic waste is filled batch-wise into simple garage-like
digesters for about 30-40 days.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Experts report that this process
has a high potential for application in developing countries as it has the
simplest design and the solid waste digesters are the least expensive ones.
Also, substrates that lead to operating problems during wet fermentation due
to their structure or the proportion of impurities they contain can still be
processed using dry fermentation methods. However, up to date, there is no
experience with this technology in developing countries. Therefore, our idea
is to develop a dry-fermentation biogas plant adapted to the situation in
developing countries using locally available material.
<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">After visiting a Bekon biogas
plant in Switzerland, I’m especially concerned regarding the opening of the
digester for emptying and refilling. Before opening the door, the digester
has to be vented in order to avoid a gas-air-mixture which is explosive.
This installation seems to me rather
complicated.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">- Is anybody of you familiar
with discontinuous dry-fermentation systems and has an idea how the security
can be assured in a developing country context? Is it possible to install a
simpler venting system?<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">- Likewise, when removing the
drum from a floating-drum digester for emptying, how is ensured that at no
time an explosive gas-air-mixture occurs?<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Thanks for your
ideas,<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Yvonne</SPAN></FONT><FONT
size=5><SPAN style="FONT-SIZE: 18pt"><o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=5><SPAN
style="FONT-SIZE: 18pt">°°°</SPAN></FONT><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> <o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt">Yvonne Vögeli<BR>Eawag / Sandec<BR>Überlandstrasse
133<BR>P.O. Box 611<BR>8600 Dübendorf<BR>Switzerland<BR>Phone: +41 (0)44 823
54 20<BR>Fax: +41 (0)44 823 53
99<BR>yvonne.voegeli@eawag.ch<BR></SPAN></FONT><SPAN lang=DE-CH><A
href="http://www.sandec.ch"><FONT face=Arial size=2><SPAN lang=EN-US
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">http://www.sandec.ch</SPAN></FONT></A>
</SPAN><o:p></o:p></P>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P>
<DIV class=MsoNormal style="TEXT-ALIGN: center" align=center><FONT
face="Times New Roman" size=3><SPAN style="FONT-SIZE: 12pt">
<HR align=center width="100%" SIZE=2>
</SPAN></FONT></DIV>
<P class=MsoNormal style="MARGIN-BOTTOM: 12pt"><FONT face="Times New Roman"
size=3><SPAN
style="FONT-SIZE: 12pt">_______________________________________________<BR>Digestion
mailing list<BR><BR>to Send a Message to the list, use the email
address<BR>Digestion@bioenergylists.org<BR><BR>to UNSUBSCRIBE or Change your
List Settings use the web
page<BR>http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org<BR><BR>for
more information about digestion, see<BR>Beginner's Guide to
Biogas<BR>http://www.adelaide.edu.au/biogas/<BR>and the Biogas Wiki
http://biogas.wikispaces.com/<o:p></o:p></SPAN></FONT></P></BLOCKQUOTE></DIV>
<P>
<HR>
<P></P>_______________________________________________<BR>Digestion mailing
list<BR><BR>to Send a Message to the list, use the email
address<BR>Digestion@bioenergylists.org<BR><BR>to UNSUBSCRIBE or Change your
List Settings use the web
page<BR>http://lists.bioenergylists.org/mailman/listinfo/digestion_lists.bioenergylists.org<BR><BR>for
more information about digestion, see<BR>Beginner's Guide to
Biogas<BR>http://www.adelaide.edu.au/biogas/<BR>and the Biogas Wiki
http://biogas.wikispaces.com/<BR><BR></BLOCKQUOTE></BODY></HTML>