Microaerobic desulphurisation unit: A new biological system for the removal of H2S from biogas

A new biotechnology for the removal of H2S from biogas was devised. The desulphurisation conditions present in microaerobic digesters were reproduced inside an external chamber called a microaerobic desulphurisation unit (MDU). A 10 L-unit was inoculated with 1 L of digested sludge in order to treat the biogas produced in a pilot digester. During the 128 d of research under such conditions, the average removal efficiency was 94%. The MDU proved to be robust against fluctuations in biogas residence time (57–107 min), inlet H2S concentration (0.17–0.39% v/v), O2/H2S supplied ratio (17.3–1.4 v/v), and temperature (20–35 °C). Microbiological analysis confirmed the presence of at least three genera of sulphide-oxidising bacteria. Approximately 60% of all the H2S oxidised was recovered from the bottom of the system in the form of large solid S0 sheets with 98% w/w of purity. Therefore, this system could become a cost-effective alternative to the conventional biotechniques for biogas desulphurisation.