[Digestion] Biogas conversation rates

Duncan Martin duncanjmartin at gmail.com
Sat Jan 15 03:51:03 CST 2011


Hi Loe

A few quick comments:

1. You can check equivalences yourself by looking up the calorific values
(heating values) of the three reference fuels. Go back to the raw data,
rather than relying on the interpretations of others - who may well be
biased. The data is readily available and it needs no more specialized
knowledge to calculate equivalences than it does to calculate a currency
conversion - which I am sure you could do in your sleep! *

2. Some of these fuels (eg biogas, firewood) are q variable so all
equivalences would be best expressed as ranges. That might be one reason for
the inconsistencies you mention. Make sure your source isn't based on
biomethane - ie purified biogas.

3. Rating biogas per so many hours of cooking is meaningless unless better
defined - are you assuming an open gas ring, an enclosed oven or what**?
Just one burning at a time? What kind of food is being cooked - because some
foods need long, slow cooking? (Maybe a better yardstick would be a typical
daily household consumption.)

4. Rating biogas per so many hours of lighting is equally meaningless. How
many lights? What output? A reasonable assumption for this application might
be a single ~40W-equivalent to light a single room  - but state it.

* If that sounds unhelpful, it comes from long experience of university
teaching - and exposure to a lot of "*I am a student and I need someone to
do my assignment for me*" requests! You'll learn more if you learn how to
work it out for yourself.

** A well known problem here is that the poorest people often (though not
always) use the least efficient cooking methods - eg an open fire. A common
site in urban Zimbabwe a few years ago was a pot suspended above an electric
fire laid on its back!!!

Duncan Martin
Cloughjordan Ecovillage
Ireland

On 12 January 2011 13:52, Franssen, Loe (Alumni) <
LLC.Franssen at alumni.maastrichtuniversity.nl> wrote:

>  Dear biogas experts,
>
> I am a 22 year old student from the Maastricht University where I am doing
> a bachelor in International Business. I am currently doing an internship for
> a Dutch biogas company that is planning to sell systems in East Africa. I am
> developing a huge mathematical model that calculates - among other things -
> how big (m³) a digester should be for those households. I want to determine
> this on the basis of the kilo’s of charcoal and firewood and liters of
> kerosene they already use and also on the basis of cooking time and lighting
> hours. After studying several articles from GTZ, SNV, and master or Phd.
> students’ reports I came to the following conversion rates and I was hoping
> you guys could give your opinion on it.
>
> Source
>
> Charcoal (kg) >> Gas (l)
>
> 500
>
> GTZ article Biogas digest volume 1<http://www.gtz.de/de/dokumente/en-biogas-volume1.pdf>
>
> GTZ article Biogas digest volume 1
>
> firewood (kg) >> Gas (l)
>
> 200
>
> Kerosene (l) >> Gas (l)
>
> 1600
>
> *   link 1<http://www.shvoong.com/humanities/1957301-biogas-making-technique-simplified/>
> *
>
> *link 2<http://www.inseda.org/Presentation/Biogas-the%20future%20Sustainable%20Energy-Fr%20Mathew.pdf>
> *
>
> *link 3<http://www.eplantscience.com/index_files/biotechnology/Biotechnology%20and%20environment/Biomass%20Energy%20(Bio-energy)/biotech_bio-energy_gaseous_fuels.php>
> *
>
> Cooking (hrs) >> Gas (l)
>
> 300
>
> Lighting (hrs) >> Gas (l)
>
> 70
>
> SNVworld.org link4<http://www.snvworld.org/en/Documents/Biogas_stoves_and_lamps_test_report_2009.pdf>
>
>
> I am particularly concerned about the conversion rate from liters of
> kerosene to liters of biogas. The results I found online don’t seem to be
> very constant. I tried to do some calculations myself but I have no idea how
> to calculate this (my background is (micro-) finance) so I was hoping you
> could shed some lights on these numbers!!
>
> Kind regards,
>
> Loe Franssen Maastricht University student
>
>
>
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> Beginner's Guide to Biogas
> http://www.adelaide.edu.au/biogas/
> and the Biogas Wiki http://biogas.wikispaces.com/
>
>
>
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