Improved organic matter biodegradation through pulsed H₂ injections during in situ biomethanation

During in situ biomethanation, microbial communities can convert complex Organic Matter (OM) and H₂ into CH₄. OM biodegradation was compared between Anaerobic Digestion (AD) and in situ biomethanation, in semi-continuous processes, using two inocula from the digester (D) and the post-digester (PoD) of an AD plant. The impact of H₂ on OM degradation was assessed using a fractionation method. Operational parameters included 20 days of hydraulic retention time and 1.5 g_VS.L^-1.d^-1 of organic loading rate. During in situ biomethanation, 485 NmL of H₂ were injected for each feeding (3 times a week). Maximum organic COD removal was 0.6 gCOD in AD control and at least 1.6 gCOD for in situ biomethanation. Therefore, COD removal was 2.5 times higher with H₂ injections. These results bring out the potential of H₂ injections during AD, not only for CO₂ consumption but also for better OM degradation.