Started with the 13th editon!

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I think that a generalized equation would be difficult at best due to the various enzymatic pathways possible.  Just as an example: various anaerobic bacteria ferment glycerol and produce butyric or propionic with valeric and caproic acids observed at smaller concentrations.

E. coli happens!

Database Central

Buswell equation for predicting methane yield:

Both these equations are greatly simplified, ignoring intermediate products and cell formation. The Buswell equation also ignores nitrogen in the reaction. Nonetheless, these relationships are useful for estimating reaction stoichiometry.