small molecules (from previous process) were converted to Volatile
Fatty Acids (VFAs)
• VFAs such as formic acid, acetic acid, propionic acid, butyric acid
(Which is low molecular weight (Chain of C < 5))
• CO2 and H2, also, were formed
• Then Acetogenesis occurs by acetogenic bacteria — VFAs were
converted to acetic acid
• decrease VFAs concentration