[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
>> 
>>_______________________________________________
>>Digestion mailing list
>>
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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 
>http://www.adelaide.edu.au/biogas/ and the Biogas Wiki 
>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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