Impact of an anoxic desulfurization process on methane content of the purified biogas

This study showed the impact of an anoxic desulfurization process on the CH4 and CO2 content of the purified biogas. The desulfurization system was implemented in an anoxic bioscrubber, which supported H2S removal efficiencies ranging from 92 +/- 8 to 97 +/- 6% for H2S loading rates between 28.3 and 37.8 g S mliquid-3 h- 1. CO2 absorption during the desulfurization process mediated a slight reduction in the CO2 concentration from 39.5% in the raw biogas to 36.5-38.2% in the purified biogas. Such reduction in the CO2 concentration was propor-tional to the increase of CH4 concentration recorded, passing from 60.0% in the raw biogas to 61.7-63.5% in the purified biogas. Bacterial community characterization by means of 16S rRNA high-throughput sequencing revealed the consistent presence of both methanotrophs (Methylibium, Methylomonas and Methylosinus genera) and methanol-oxidizing denitrifiers (Simplicispira and Methyloversatilis genera), which suggested that methane oxidation indeed occurred. The quantification of a potential CH4 uptake in the desulfurization process was hindered by the CO2 absorption observed, however, strategies for quantifying biological CH4 consumption in anoxic desulfurization systems are proposed and discussed, based on the results herein obtained.

Automated summary

This study demonstrated that anoxic desulfurization process can impact the CH4 and CO2 content of purified biogas. The reduction in CO2 concentration and increase in CH4 concentration in the purified biogas were found to be proportional, with CO2 absorption playing a role in this process. Additionally, the presence of methane-oxidizing bacteria suggests that methane oxidation occurred in the desulfurization system.