Innovative ex-situ biological biogas upgrading using immobilized biomethanation bioreactor (IBBR)

Abstract

Biogas, which typically consists of about 50–70% of methane gas, is produced by anaerobic digestion of organic waste and wastewater. Biogas is considered an important energy resource with much potential; however, its application is low due to its low quality. In this regard, upgrading it to natural gas quality (above 90% methane) will broaden its application. In this research, a novel ex-situ immobilized biomethanation bioreactor (IBBR) was developed for biologically upgrading biogas by reducing CO2 to CH4 using hydrogen gas as an electron donor. The developed process is based on immobilized microorganisms within a polymeric matrix enabling the application of high recirculation to increase the hydrogen bioavailability. This generates an increase in the consumption rate of hydrogen and the production rate of methane. This process was successfully demonstrated at laboratory-scale system, where the developed process led to a production of 80–89% methane with consumption of more than 93% of the fed hydrogen. However, a lower methane content was achieved in the bench-scale system, likely as a result of lower hydrogen consumption (63–90%). To conclude, the IBBRs show promising results with a potential for simple and effective biogas upgrading.

Hydrogenotrophs-Based Biological Biogas Upgrading Technologies

“…Other strategies for improving the mass transfer rate are as follows. Burkhard et al (2015) and Baransi-Karkaby et al (2020) immobilized the microorganisms to avoid issues with gas-liquid transfer and to provide direct contact between the gas and microorganisms. Their studies resulted in 89–98% of CH 4 content, respectively.…”

Enhancing methane production in anaerobic digestion through hydrogen assisted pathways – A state-of-the-art review

“…The application of HM based AD can be obtained through three approaches: (a) when H2 is added directly into the reactor, in-situ method, (b) when H2 is allowed to react with CO2 in a separate reactor as a post-treatment, succeeding the anaerobic digester reactor, as ex-situ approach and (c) hybrid technology combining both in-situ and ex-situ approaches [55,56].…”

Spiral-Pipe Gas Anaerobic Digester

“…The highest η CO 2 and η H 2 were obtained at a GFR of 3.9 L L r –1 d –1 , at which the CH 4 content was consistently maintained above 95%. This CH 4 content surpasses that achieved by the novel process of Baransi-Karkaby et al, which yielded 80–89% CH 4 but consumed >93% of the H 2 . Ghofrani-Isfahani et al investigated the impact of diffusers with different pore sizes on biogas-upgrade capacity.…”