Biogas upgrading from vinasse digesters: a comparison between an anoxic biotrickling filter and an algal‐bacterial photobioreactor

BACKGROUND Biological technologies for biogas upgrading such as anoxic biotrickling filters ( BTF ) and algal–bacterial photobioreactors ( PBR ) constitute a cost‐effective, environmentally friendly alternative to conventional physical–chemical methods. Nonetheless, there is a lack of studies comparing their performance when treating real biogas. RESULTS A H 2 S removal efficiency >98% was consistently recorded in both systems, with elimination capacities up to 26 and 12.4 g S‐ H 2 S m −3 h −1 in the BTF and PBR , respectively, at empty bed residence times ( EBRTs ) of ∼ 30 min. Both bioreactors demonstrated a high robustness towards fluctuations in biogas composition and flowrate, maintaining nearly complete desulfurization despite the variations in sulfur load and EBRT . The BTF also showed an immediate recovery from a 15 days operational shut‐down, and the ability to utilize the nutrients from nitrate‐supplemented digestate during biogas desulfurization. In addition, the PBR supported an average CO 2 removal of 23.0 ± 11.8%, increasing to 62% at higher pH of 8.1, with a carbon fixation rate of 285 mg CO 2 L −1 d −1 . CONCLUSIONS The BTF was confirmed as a robust technology for the desulfurization of real biogas, even when supplemented with effluent from the digester. High H 2 S removal was also achieved in the PBR , the CO 2 fixation capacity of microalgae enhancing biogas purification. © 2015 Society of Chemical Industry