The model shows that hydrogen ion concentration (pH) controls
the acetic acid (HAc) degradation (mol of decomposed
HAc/mol of initial HAc), high H+ concentration leads to low
decomposition. The modelled equilibrium pH value of approximately
4 (cf. pKaof HAc), however, are low in comparison
to empirical observations (pH 7–8). This phenomenon results
from the initial substrate (acetic acid). The pH value does
not affect the methane yield (mol of produced CH4/mol of
HAc decomposed) but it does change the solubility of carbon
dioxide.