Question

If pH drops below 6 in an anaerobic digester, then methane production decreases because

• A. Hydrolysis stops
• B. Methanogens are inhibited
• C. Oxygen increases
• D. Sulfates increase

Hint:

Anaerobic digestion: \[ \boxed{ \begin{aligned} \text{Optimum pH} &\approx 6.8-7.5\\ \text{Low pH} &\rightarrow \text{Methanogens inhibited}\\ \text{Methane production} &\downarrow \end{aligned} } \]

Answer 1

The Correct Option is B

Step 1: Recall the pH preference of methanogens.
Methanogenic archaea are quite sensitive organisms that thrive only in a narrow, near neutral pH band, roughly between 6.8 and 7.5.
Step 2: See what a pH drop does to them.
Once the digester pH falls below 6, this becomes too acidic for methanogens, and their enzyme systems stop working efficiently.
Step 3: Connect this to methane output.
With the methanogens themselves suppressed, methane generation slows down directly, rather than because hydrolysis or oxygen levels changed.
\[ \boxed{\text{Methanogens are inhibited}} \]