Anaerobic digestion fundamentals — Biogas production is best described as:

Introduction / Context:
Biogas (a mixture dominated by methane and carbon dioxide) is formed by consortia of anaerobic microbes. Their metabolic rates and community balance are highly sensitive to temperature, which affects enzyme kinetics, gas solubility, and the growth of key functional groups (hydrolyzers, acidogens, acetogens, and methanogens).

Given Data / Assumptions:

• Standard operating windows: psychrophilic (<20°C), mesophilic (~25–40°C), thermophilic (~50–60°C).
• Oxygen is detrimental; strict anaerobiosis is required.
• We are comparing temperature dependence versus oxygen dependence.

Concept / Approach:
Methanogenesis increases markedly with temperature up to a stability limit. Each range has characteristic gas yields, start-up times, and pathogen reduction profiles. Because oxygen inhibits obligate anaerobes, biogas production is not oxygen-dependent; it is actually oxygen-sensitive. Therefore, the most accurate descriptor is “temperature-dependent.”

Step-by-Step Solution:

Verification / Alternative check:
Operational handbooks specify different setpoints and retention times for mesophilic vs thermophilic digesters, reflecting temperature dependence of kinetics and stability.

Why Other Options Are Wrong:

• Temperature-independent: contradicts observed sensitivity and setpoint control.
• Oxygen-dependent: opposite of anaerobic digestion requirements.
• None: unnecessary since one option is clearly correct.

Common Pitfalls:
Ignoring temperature shocks that cause foaming or acidification; digesters need gradual adjustments.

Final Answer:
a temperature-dependent process