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 (NaHCO 3 ) 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 NaHCO 3 /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 CH 4 /g VS) and methane concentration in biogas (78%) was obtained, using 11% NaHCO 3 mass/mass residue, and industrial sludge as inoculum. NaHCO 3 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. • NaHCO 3 acts efficiently as an alkalizing and buffering agent for FW AD. • NaHCO 3 , 11% (m/m), provided a methane potential of 214 NmL CH 4 /g VS for FW AD. • NaHCO 3 (11%, m/m) favored the generation of biogas with 78% methane for FW AD. • Absence or excess NaHCO 3 interferes with the methane potential obtained for FW AD.