Table 5 Optimal environmental parameters for a stable anaerobic digestion

pH

Hydrolysis and acidogenesis (two-phrase anaerobic digestion)

5.5–6.5

[91]

Methanogenesis (two-phase anaerobic digestion)

6.5–8.5

[15, 91]

Mixed reactor liquid (one-phase anaerobic digestion)

6.7–7.8

[27, 42]

(PH₂) (Hydrogen Partial pressure)

Mixed reactor liquid (one-phase anaerobic digestion)

10⁻⁴–10⁻⁵ atm

[27, 42]

Alkalinity

Mixed reactor liquid (one-phase anaerobic digestion)

1200–2300 mg

CaCO₃ per litre

[118]

C:N ratio

Mixed reactor liquid (one-phase anaerobic digestion)

20–30

[15, 38]

NH₃-Nitrogen

Mixed reactor liquid (one-phase anaerobic digestion)

50–200 mg per litre

[118]

Free NH₃

Mixed reactor liquid (one-phase anaerobic digestion)

<150 mg per litre

[118]

H₂S

Mixed reactor liquid (one-phase anaerobic digestion)

<200 mg per litre

[54]

Heavy metals

Mixed reactor liquid (one-phase anaerobic digestion)

<10⁻⁴ M

[27]