[Digestion] Calculating Methane Generation

[Warren Weisman]

Eric, 

You're asking the million dollar question, but the
answer is methane production is a variable and no one
has done a definitive work on it, yet. There's no way
to predict it with great accuracy---which makes it so
fun to work with! 

But you might find some use in METHANE GENERATION FROM
HUMAN, ANIMAL AND AGRICULTURAL WASTES by the National
Academy of Sciences. It predicts a methane
production---separated from biogas---between 3.6-4.8
cubic feet per pound of volatile solids over 15 days.
but, of course there's things---like gas recirculation
and better stirring---that can be done to improve gas
production and of course, lots you can do to reduce
it, too! The above mentioned book has exhaustive
footnotes and references. Another helpful resource is
A CHINESE BIOGAS MANUAL---which is the small digester
standard at this time.  

Warren Weisman, USA 

--- Eric Fitch <fitch at springstreetgarage.com> wrote:

> Dear AD Listers,
> 
>  
> 
> Can anyone site a credible reference that explains
> how to calculate the
> methane output from a proposed digester with a known
> feedstock?  I am
> looking for a valid set of equations where inputs
> would be measurable
> properties like COD, TSS, VS, etc. and the output
> would be a normalized
> result, like mass of methane produced per mass of
> COD input.
> 
>  
> 
> I have found conflicting references while searching
> the web that result in
> an order of magnitude variation.  Unfortunately this
> spread straddles the
> point of viability for this project.  In order to
> move forward I need more
> confidence in the expected methane output.
> 
>  
> 
> Thank you in advance for your help.
> 
>  
> 
> Sincerely,
> 
> Eric Fitch
> 
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>
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> 


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