Regulatory influence of CO2 supplementation on fermentative hydrogen production process

This study presents an approach to enhance fermentative biohydrogen (H2) production by improving the system buffering capacity through utilization of CO2 generated from syngas. The experimental data substantiates the positive impact of CO2 sparging on H2 production process. Various CO2 sparging times viz., 30, 60 and 120 s were evaluated on H2 production and substrate degradation. Based on the optimum sparging time (60 s), experiments were further performed to study the influence of pH microenvironment (5, 6 and 7) on the process efficiency. Further the influence of periodic CO2 sparging was also evaluated. Experimental data visualized a marked improvement on the overall process performance based on H2 production and substrate degradation after sparging CO2. Carbonic acid upon association/dissociation forms bicarbonates in the system. Alkaline condition helps to build up buffering nature, which resist fluctuations in pH even at higher VFA concentrations. Substrate degradation was effective during intermittent sparging at neutral conditions. CO2 sparging directly effecting the bulk liquid environment of the system improves buffering nature which indirectly helps to maintain favorable microenvironment for biohydrogen production process.