Where does the common assumption for biogas weight from water come from?

[MartinLe]

A common assumption is that, with anaerobic digestion, 13% of the mass of the gas come from water, the rest from VS.
I understand from the Buswell or Buswell Boyle equation that some water is dissociated, as an oxygen source for the CO2.

Now what I don't nderstand is where exactly the number 13% comes from.
Calculating from the buswell equation, I'd assume 0% for fiber, 30% for protein and 50% for fat. This is of course based on some assumptions what the relevant protein/fat is composed like. So I assume someone, somewhere did either the math or took measurements and arrived at 13% and this number gets tossed around since then in the wastewater field and from there into other fields of anaerobic digestion. Now I'm not sure if it is safe to assume those 13% everywhere else.
So what did the person measure/caclulate?

 

[adalinaabella]

I think it's better to go through with the chemical lab and do the experiment with and expert.


Who will show you where your from the common assumption for biogas weight from water come from.


Because, I can not answer exactly what happened, so it's better to get an exact answer rather to live with a false one.

Thanks!
magicrubbishclearance

 

[IRstuff]

The problem is the assumption. The equation is configured to work with different substrates with different compositions

http://www.renewable-energy-concepts.com/biomass-bioenergy/biogas-basics/buswell-and-boyle.html

TTFN
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