Choose the correct option based on the given assertion and reason.
Assertion (A): Biogas production is reduced in winters. Reason (R): Methanogenesis occurs at mesophilic temperatures.
Choose the correct answer from the options given below:

Correct option is A

Explanation:
Biogas production is primarily driven by the process of methanogenesis, which is carried out by methanogenic bacteria. These bacteria are mesophilic, meaning they function optimally at moderate temperatures (typically 30–40°C).
During winters, the ambient temperature drops significantly, reducing the metabolic activity of methanogens. As a result, biogas production declines because the microbial activity slows down.
Since methanogenesis is temperature-dependent, and the efficiency of the process decreases in colder conditions, the reason (R) correctly explains the assertion (A).
Thus, option (a) is correct.
Information Booster:
· Biogas composition: Mainly consists of methane (CH₄) (50-70%) and carbon dioxide (CO₂) (30-40%).
· Methanogenic bacteria: Belong to the Archaea domain and thrive in anaerobic conditions.
· Types of methanogens:
· Psychrophilic (0-20°C) – Active in cold environments.
· Mesophilic (30-40°C) – Most common in biogas plants.
· Thermophilic (50-60°C) – More efficient but require high energy input.
· Winter effects on biogas plants:
· Reduced microbial activity.
· Longer retention time required for digestion.
· Need for heating mechanisms to maintain efficiency.
· Solutions for winter biogas production:
· Insulating digesters.
· Using thermophilic bacteria.
· Pre-heating feedstock before digestion.
Additional Information:
· (A) Biogas production is reduced in winters – True because lower temperatures slow down methanogenic bacterial activity.
· (B) Methanogenesis occurs at mesophilic temperatures – True since most biogas-producing bacteria thrive in the 30-40°C range.
· Effect of temperature on biogas: Lower temperatures slow down digestion, reducing methane yield.
· Ideal temperature maintenance: Many biogas plants use solar heating or insulated digesters to maintain efficiency.