Effect of microalgae storage conditions on methane yields.

Area of Science:

• Biotechnology and Bioengineering
• Renewable Energy
• Environmental Science

Background:

• Anaerobic digestion of microalgae biomass is a key area for renewable energy research.
• Methane yields can vary significantly, often attributed to microalgae strains or inoculum properties.
• The effect of biomass storage conditions on anaerobic digestion performance is less understood.

Purpose of the Study:

• To investigate the impact of microalgae biomass processing and storage on methane yields and hydrolysis kinetics.
• To determine if biomass storage conditions influence the efficiency of anaerobic digestion.
• To provide insights for standardizing microalgae biomass handling in research.

Main Methods:

• Batch mode anaerobic digestion assays were performed using fresh, frozen, freeze-dried, and refrigerated microalgae biomass.
• Hydrolysis kinetics were analyzed by measuring methane production over time.
• Macromolecular profiles of the biomass were assessed.
• A semi-continuous reactor was operated with stored biomass.

Main Results:

• Frozen microalgae biomass doubled the hydrolysis constant and increased methane yield by 1.56-fold compared to fresh biomass.
• Freeze-dried biomass showed similar enhancements, while refrigerated biomass (4°C) yielded slightly lower improvements.
• Nitrogen mineralization was higher in stored biomass, but methane production in a semi-continuous reactor was unaffected by 28-day storage at 4°C.

Conclusions:

• Biomass storage conditions, particularly freezing and freeze-drying, significantly enhance anaerobic digestion performance.
• The state of microalgae biomass upon storage is a critical factor influencing methane yield and hydrolysis kinetics.
• Standardizing biomass storage protocols is essential for reliable and comparable results in microalgae-based anaerobic digestion research.