[Digestion] Biogas conversation rates
Eric Buysman
ericishier at yahoo.com
Mon Jan 17 15:24:16 CST 2011
Dear Leo, dear all,
Leo, experiences show that the first use of biogas from household biogas units
is cooking. Hence, I advice you, to dedicate most attention to that. Lighting is
secondary. Also, biogas for lighting is used, but only if an electrical powered
alternative is not avialable. Then using average values of GTZ might misguide
you, as these could have been obtained from different stoves with
different efficiencies. The best conversion of the fuels is to convert all the
fuels into amounts of useful energy. With useful energy I mean the amount of
fuel that is actually diverted to cooking and not lost.
Something like this:
Net calorific value of fuel a * amount * stove efficiency = Amount of energy
used for cooking.
Then when knowing the amount of energy used for cooking, you can, when knowing
the efficiency of a biogas stove and the net calorific value of biogas calculate
the amount of biogas equivalents. There is a wealth of literature on stove
efficiencies and biogas stove efficiencies.
Regarding your question about the calorific value of charcoal, well, since wood
is already 15.6 MJ/kg, the value of charcoal, even when produced in suboptimal
conditions is very likely to be higher.
Finally, also consider this, energy demand is likely to be higher when people
have biogas, as they might currently suffer from suppressed energy demand.They
might therefore need a bigger biogas unit than you would estimate. This btw,
applies in particular to lighting!
PS, groetjes aan Sanne, dit is voor Simgas, of niet?
________________________________
From: David Fulford <davidf at kingdombio.com>
To: For Discussion of Anaerobic Digestion <digestion at lists.bioenergylists.org>
Cc: "Franssen, Loe (Alumni)" <LLC.Franssen at alumni.maastrichtuniversity.nl>
Sent: Mon, January 17, 2011 8:43:47 AM
Subject: Re: [Digestion] Biogas conversation rates
Loe, Hello,
The key to the problem is efficiencies (or more to the point:
inefficiencies). Getting light from burning kerosene or biogas is very
inefficient, as most of the energy is turned into heat. The temperature of a
wick lamp burning kerosene is about 290 deg.C = 563 K. The energy at
different frequencies is defined by Planck's law, which is can be simplified
using Wein's displacement law (see Wikipedia pages). This suggests that less
than 0.01% of the total radiation from a flame at this temperature is in the
visible spectrum.
A gas lamp burns at a higher temperature (at least 1200 K). The heat is used
with a mantle that uses a rare earth that generates light when heated. The
overall efficiency is still fairly low (perhaps 1 to 3%), but it is much
higher (100 times) than for a kerosene wick lamp.
If you comparing like with like, it would be better to compare a kerosene
pressure lamp with a biogas lamp, as pressure lamps also use mantles. I do
not know how much kerosene a kerosene pressure lamp uses, but it provides a
much better light than a wick lamp.
So your figures are not at all surprising; you need to include overall
efficiency figures when comparing the light from fuels using calorific
values.
Regards,
David
On 16/01/2011 12:34, Franssen, Loe (Alumni) wrote:
>Hey Duncan (and the others),
>
>thanks for your elaborate answer ! I'm sorry for being unspecific. Let
>me be a bit more specific and take the kerosene conversion rate
>because the information on this one is the most inconsistent.
>
>Assumptions
>Consumption rate simple wick kerosene lamp; 0,01 liter kerosene per
>hour
>
> Biogas lamp; 70 liters of gas per hour
>(specifications of the lamp that will be supplied:
>http://kingoni.en.ec21.com/Biogas_Lamp--3003470_3352352.html)
>Lumen output of a simple wick kerosene lamp 7,8 lumen
> biogas lamp; 50 lumen (not sure on this
>number as there is a large range for it right?!)
>Calculation
>
>so 1 liter of kerosene is equivalent to 7000 liter gas. After
>correcting for lumen output, 1 liter of kerosene is equal to 1,077
>liter of gas
>
>If i use calorific values i get the following result
>1kilo kerosene = 46 mj/kg with a density of 0,95 kg/l so
>1 liter kerosene = 43,7 mj/l
>1m3 biogas is 22.5mJ
>1 liter biogas = 0,0225 mJ
>
>1L kerosene = (43.7/0.0225) = 1942,22L biogas
>
>Quite a difference hm probably because of the lumen i took for the
>biogas lamp and the consumption rates?! do you have recommendations on
>these numbers?
>
>Then another small question.. for anthracite charcoal i found a
>calorific value of 27mJ/kg, for lignite charcoal 15 mj/kg. I'm talking
>about charcoal that these rural african farmers simply make in their
>backyard. i assume i should take 15 mj/kg then right?! or even less?
>
>
>Thanks again!
>
>
________________________________
Van: digestion-bounces at lists.bioenergylists.org
[digestion-bounces at lists.bioenergylists.org] namens Duncan Martin
[duncanjmartin at gmail.com]
>Verzonden: zaterdag 15 januari 2011 10:51
>Aan: For Discussion of Anaerobic Digestion
>Onderwerp: Re: [Digestion] Biogas conversation rates
>
>
>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
>>GTZ article Biogas digest volume 1
>>firewood (kg) >> Gas (l) 200
>>Kerosene (l) >> Gas (l) 1600 link
>>1 link 2 link 3
>>
>>
>>
>>
>>
>>
>>
>>Cooking (hrs) >> Gas (l) 300
>>
>>
>>
>>Lighting (hrs) >> Gas (l) 70 SNVworld.org
>>link4
>>
>>
>>
>>
>>
>>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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>>
>>for more information about digestion, see
>>Beginner's Guide to Biogas
>>http://www.adelaide.edu.au/biogas/
>>and the Biogas Wiki http://biogas.wikispaces.com/
>>
>>
>>
>
> _______________________________________________ Digestion mailing list to Send
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> for more information about digestion, see Beginner's Guide to Biogas
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>http://biogas.wikispaces.com/
>
--
********************************************************************
Dr David Fulford CEnv MEI, 15, Brandon Ave, Woodley, Reading RG5 4PU
d.j.fulford at btinternet.com, Tel: +44(0)118 326 9779 Mob: +44(0)7746
806401
Kingdom Bioenergy Ltd, www.kingdombio.com, davidf at kindombio.com
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