Work

Hydrogen and Methane Production in Two-Stage Upflow Anaerobic Sludge Blanket Reactors from Crude Glycerol

Year: 2024

Type: article

Abstract: This study aimed to investigate the impact of operational conditions, such as hydraulic retention time and substrate concentration, on the production of hydrogen (H 2 ) in an upflow anaerobic sludge blanket (UASB) reactor, which was followed by the production of methane (CH 4 ) in a sequential UASB fed with acidogenic effluent. The maximum yield of H 2 obtained was 0.23 ± 0.05 mol H 2 /mol glycerol (∼8% of the maximum theoretical yield) by applying a maximum organic loading rate (OLR) of 50 kgCOD/m 3 ·d. The soluble metabolites detected in the UASB-H 2 effluent showed that 1,3-propanediol was the primary metabolite formed during the operation (1.8–3.7 g/L). UASB-CH 4 was operated stably with a maximum OLR of 19 kgCOD/m 3 ·d, removing 94% of organic matter and producing 0.092 m 3 of biogas daily (74% of CH 4 ). The ecological succession analysis of the UASB-H 2 showed the bacterial population parameters increase at average OLRs, promoting the dominance of generalist species because of a higher carrying capacity from a less specific substrate and increasing system stability because of niche diversification. An energy analysis was conducted in the condition with the highest daily CH 4 production, that is, 18.72 kgCOD/m 3 ·d. The two-stage system resulted in 171 MJ/m 3 reactor·d for a plant generating 34,350 kgCOD/d of glycerol. In contrast, a single CH 4 production system would be capable of generating only 94 MJ/m 3 reactor·d. Therefore, although hydrogen production was low in the hydrogenogenic reactor, acidogenesis in the first UASB reactor allowed the methanogenic reactor to achieve high OLR and, consequently, high energy yields.

Source: Industrial Biotechnology

DOI: 10.1089/ind.2024.0008