Siloxane removal from biogas by biofiltration: biodegradation studies

Recently a lot of attention has been focused on volatile methyl siloxanes (VMSs) in biogas because of the costly problems deriving from the formation of silicate-based deposits in biogas-fuelled power plant equipments. Currently, VMSs are removed from biogas with high operational costs by adsorption on activated carbons. Biofiltration could be a cost-effective and environmentally friendly alternative to current technologies, leading to a decrease in the cost of biogas treatment, therefore enhancing its use for power generation. This document presents the results of biodegradation studies on VMSs aimed to investigate the possibility of using biofiltration to treat biogas. Growth of bacteria isolated from activated sludge with octamethylcyclotetrasiloxane (D4) in the vapour phase as the only carbon source was observed. 16S-rDNA-sequencing showed that the mixed population mainly contained γ-proteobacteria; within these, Pseudomonas was the dominating genus. A biotrickling filter was set up to treat different air flows with a siloxane concentration varying between 45 and 77 mg m⁻³. Measurements on the gas output revealed removal efficiency up to 20% compared to a control in sterile conditions.