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Table 3 Free energy values of key acetogenic and methanogenic reactions of anaerobic digestion

From: Biomass waste-to-energy valorisation technologies: a review case for banana processing in Uganda

AD step Reaction G 0 (kJ mol−1)*
Acetogenesis
 Propionate → Acetate \({\text{CH}}_{ 3} {\text{CH}}_{ 2} {\text{COO}}^{ - } + 3 {\text{H}}_{ 2} {\text{O}} \to {\text{CH}}_{ 3} {\text{COO}}^{ - } + {\text{H}}^{ + } + {\text{HCO}}_{3}^{ - } + 3 {\text{H}}_{ 2}\) +76.1
 Butyrate → Acetate CH3CH2CH2COO + 2H2O → 2CH3COO + H+ + 2H2 +48.1
 Ethanol → Acetate CH3CH2OH + H2O → CH3COO + H+ + 2H2 +9.6
 Lactate → Acetate \({\text{CH3CHOHCOO}}^{ - } + 2 {\text{H}}_{ 2} {\text{O}} \to {\text{CH}}_{ 3} {\text{COO}}^{ - } + {\text{H}}^{ + } + {\text{HCO}}_{3}^{ - } + 2 {\text{H}}_{ 2}\) −4.2
 Formate → Acetate \(2 {\text{HCO}}_{3}^{ - } + 4 {\text{H}}_{ 2} {\text{O}} + {\text{H}}^{ + } \to {\text{CH}}_{ 3} {\text{COO}}^{ - } + 4 {\text{H}}_{ 2} {\text{O}}\) −104.6
Methanogenesis
 Acetate → Methane \({\text{CH}}_{ 3} {\text{COO}}^{ - } + {\text{H}}_{ 2} {\text{O}} \to {\text{HCO}}_{3}^{ - } + {\text{CH}}_{ 4}\) −31.0
 H2/CO2 → Methane 4H2 + CO2 → CH4 + 2H2O −131.0
 Formate → Methane \({\text{HCO}}_{3}^{ - } + 4 {\text{H}}_{ 2} + {\text{H}}^{ + } \to {\text{CH}}_{ 4} + 3 {\text{H}}_{ 2} {\text{O}}\) −135.6
  1. * Temperature 298 K, pH 7, 1 M for solutes and 1 atm for gases