chemengineering Review Microbial Ecology of Biofiltration Units Used for the Desulfurization of Biogas Sylvie Le Borgne 1,* and Guillermo Baquerizo 2,3 1 Departamento de Procesos y Tecnología, Universidad Autónoma Metropolitana- Unidad Cuajimalpa, 05348 Ciudad de México, Mexico 2 Irstea, UR REVERSAAL, F-69626 Villeurbanne CEDEX, France 3 Departamento de Ingeniería Química, Alimentos y Ambiental, Universidad de las Américas Puebla, 72810 San Andrés Cholula, Puebla, Mexico * Correspondence:
[email protected]; Tel.: +52–555–146–500 (ext. 3877) Received: 1 May 2019; Accepted: 28 June 2019; Published: 7 August 2019 Abstract: Bacterial communities’ composition, activity and robustness determines the effectiveness of biofiltration units for the desulfurization of biogas. It is therefore important to get a better understanding of the bacterial communities that coexist in biofiltration units under different operational conditions for the removal of H2S, the main reduced sulfur compound to eliminate in biogas. This review presents the main characteristics of sulfur-oxidizing chemotrophic bacteria that are the base of the biological transformation of H2S to innocuous products in biofilters. A survey of the existing biofiltration technologies in relation to H2S elimination is then presented followed by a review of the microbial ecology studies performed to date on biotrickling filter units for the treatment of H2S in biogas under aerobic and anoxic conditions. Keywords: biogas; desulfurization; hydrogen sulfide; sulfur-oxidizing bacteria; biofiltration; biotrickling filters; anoxic biofiltration; autotrophic denitrification; microbial ecology; molecular techniques 1. Introduction Biogas is a promising renewable energy source that could contribute to regional economic growth due to its indigenous local-based production together with reduced greenhouse gas emissions [1].