Influence of sodium bicarbonate (NaHCO3) on the methane generation potential of organic food waste

Anaerobic digestion of food waste requires the addition of alkalinizer such as sodium bicarbonate (NaHCO3) which acts as a buffer in pH control, preventing accumulation of VFAs, contributing to increased methane production. The appropriate concentration of the alkalizer directly influences the methane generation potential of substrate. This research tested different concentrations of bicarbonate in the anaerobic digestion of food waste, using anaerobic inoculants (industrial granular sludge and flocculent sewage). Several ratios of mass percentages of NaHCO3/mass residue (%), 1.5%, 4.5%, 11%, 28%, and 111%, were tested, evaluating their effect on the methane generation potential and methane concentration in biogas in tests of biochemical potential of methane. The best methane generation potential (214 NmL CH4/g VS) and methane concentration in biogas (78%) was obtained, using 11% NaHCO3 mass/mass residue, and industrial sludge as inoculum. NaHCO3 functioned satisfactorily as a buffering agent for anaerobic digestion. The excess or the scarcity of alkalizer is harmful to anaerobic digestion, regardless of the quality of the inoculum used.