glucose $ ethanol þ carbon dioxide
ð2:2Þ
glucose þ hydrogen $ propionic acid þ water
ð2:3Þ
glucose ! acetic acid
ð2:4Þ
(Korres et al. 2013)
2.2.1.3 Acetogenesis
The third step of biogas production is acetogenesis or acetic acid production. At this
phase, acetogenic bacteria breakdown volatile fatty acids and ethanol, produced in
acedogenesis (second step), into acetate/acetic acid (CH 3 COO
À
), carbon dioxide,
and hydrogen. Acetic acid, hydrogen, and carbon dioxide are produced by
acetogenic bacteria, e.g. Syntrobacterwolinii and Syntrophomonaswolfei (Vavilin
et al. 2008).
Fig. 2.2 Anaerobic digestion process. Modified from Mao et al. (2015)
36
M. N. Anwar et al.