The use of a silicone-based biomembrane for microaerobic H2S removal from biogas

A lab-scale bio-membrane unit was developed to improve H2S removal from biogas through microaeration. Biomembrane separated biogas from air and consisted of a silicone tube covered by microaerobic biofilm. This setup allowed efficient H2S removal while minimizing biogas contamination with oxygen and nitrogen. The transport and removal of H2S, N-2, O-2, CH4 and CO2 through bare membrane, wet membrane and biomembrane was investigated. Membrane allowed the transfer of gases through it as long as there was enough driving force to induce it. H2S concentration in biogas decreased much faster with the biomembrane. The permeation of gases through the membranes decreased in order: H2S > CO2 > CH4 > O-2 > N-2. H2S removal efficiency of more than 99% was observed during the continuous experiment. Light yellow deposits on the membrane indicated the possible elemental sulfur formation due to biological oxidation of H2S. Thiobacillus thioparus was detected by FISH and PCR-DGGE

Microaeration through a biomembrane for biogas desulfurization : lab-scale and pilot-scale experiences

Microaeration, a biological method to remove H2S from biogas by oxidizing it to elemental sulfur, has been shown to be highly efficient, simple and reliable. However, dosing air directly into an anaerobic fermenter results in the dilution of biogas with nitrogen and oxygen and can cause clogging of biogas pipes by elemental sulfur. These disadvantages can be overcome by the use of a biomembrane, i.e. a membrane covered with a biofilm that separates air and biogas. Experiments with bare, wet and biofilm membranes were conducted with a commercially available PVDF LM-P2 membrane to evaluate the chemical and biological oxidation rates of H2S. Different amounts of air were dosed through the biomembrane to determine the optimum air-to-biogas ratio, to evaluate methane losses and to evaluate biogas contamination with nitrogen and oxygen. The H2S content decreased from 3000 ppm to less than 100 ppm within two days. The loss of methane was 3.7% of the total methane production and the specific H2S removal rate was 32 mg m(-2) d(-1)