Several techniques can be applied in order to achieve the required H2S concentration in biogas, including physical, chemical, or biological, or combinations of these three alternative methods. Despite their high chemical requirements, Salinosporamide A and disposal cost, physicochemical technologies are widely implemented at industrial scale due to extensive experience in design and operation. Biological processes have the potential to overcome some or all the disadvantages of physicochemical technologies (Syed et al., 2006). In fact, there are several technical solutions offered commercially worldwide for biogas desulfurization involving biological removal mechanisms, such as the combination of chemical scrubbing with a bioreactor (http://en.paques.nl/products/featured/thiopaq), or the iron-sponge-bed filter inoculated with thiobacteria, which combines chemical and biological oxidation (http://odorfilter.com/hydrogen-sulfide-removal/technologies/h6splus-systems.html).
An alternative for the desulfurization of biogas directly in the reactor consists in injecting limited amounts of O2, namely, imposing microaerobic conditions during digestion. Thus, most of the H2S is chemically and biologically oxidized to S0 (Kleinjan, 2005). This is possible because sulfide-oxidizing bacteria (SOB) are present in the sludge and proliferate in the digester (Weiland, 2010).