Thermophilic methane production from cattle waste

Area of Science:

• Biotechnology
• Environmental Science
• Chemical Engineering

Background:

• Anaerobic digestion of cattle waste is crucial for renewable energy production.
• Optimizing digester performance requires understanding the impact of operational parameters like temperature and feed concentration.

Purpose of the Study:

• To investigate methane production from cattle waste under various anaerobic digestion conditions.
• To determine optimal feed concentrations of volatile solids (VS) and retention times (RT) for efficient methanogenesis.

Main Methods:

• Utilized four 3-liter anaerobic digestors operating at 60°C.
• Systematically increased feed concentrations of volatile solids (VS) at different retention times (3, 6, 9, 12 days).
• Monitored methane production, VS destruction, pH, alkalinity, ammonia, and volatile fatty acids.

Main Results:

• Optimal fermentation occurred at 8.2% VS for 3-day RT, 10.0% for 6-day RT, and 11.6% for 9- and 12-day RT.
• Methane production rates increased with RT, reaching 0.22 L/day per g VS at 12-day RT.
• The 3-day RT digestor showed high stability and methane production (4.5 L/day per L digestor) up to 8.2% VS.
• Exceeding optimal VS concentrations led to decreased efficiency and accumulation of volatile acids.

Conclusions:

• Methane production from cattle waste can be maximized at higher loading rates than previously assumed.
• Optimized conditions allow for efficient volatile solids destruction and significant methane generation.
• The study provides valuable data for designing and operating anaerobic digesters for cattle waste treatment.