The effect of a buffer function on the semi-continuous anaerobic digestion

Area of Science:

• Environmental Science
• Biotechnology
• Chemical Engineering

Background:

• Anaerobic digestion (AD) is a key technology for waste management and renewable energy production.
• Optimizing substrate characteristics, such as the carbon-to-nitrogen (C/N) ratio, is crucial for efficient AD performance.
• Food wastes and animal slurries are abundant organic resources suitable for AD.

Purpose of the Study:

• To investigate the long-term (90-day) effects of varying C/N ratios on the anaerobic digestion of food wastes and animal slurry.
• To determine how different C/N ratios influence the characteristics and efficiency of semi-continuous anaerobic digestion.
• To understand the role of the buffer system in maintaining stable AD performance.

Main Methods:

• Semi-continuous anaerobic digestion experiments were conducted over 90 days.
• Food wastes and animal slurry were used as substrates with controlled C/N ratios.
• Key parameters such as methane (CH4) concentration, total organic carbon (TOC) utilization, ammonium (NH4+), and volatile fatty acids (VFAs) were monitored.

Main Results:

• The C/N ratio significantly impacted the characteristics of anaerobic digestion.
• Semi-continuous AD demonstrated efficiency across a wide range of C/N ratios.
• Lower C/N ratios promoted sustained methanogen activity, leading to stable high CH4 concentrations and TOC utilization.
• An active buffer system formed by NH4+ and VFAs enhanced CH4 yield, TOC utilization, and system tolerance to inhibitory compounds.

Conclusions:

• The C/N ratio is a critical factor for optimizing anaerobic digestion of food wastes and animal slurries.
• Lower C/N ratios are beneficial for long-term stable methane production and substrate degradation.
• The NH4+-VFA buffer system plays a vital role in maintaining robust and efficient anaerobic digestion.