Coupling adsorption with biotechnologies for siloxane abatement from biogas

Biogas generated during anaerobic digestion in sewage plants contains a wide spectrum of trace impurities. Siloxanes are the most hazardous pollutants and its removal is mandatory for most energy applications. The most widely used technology is adsorption onto activated carbon (AC) despite the high operating costs. In this context, the use of biotechnologies to abate biogas pollutants could assist extending the lifetime of the AC filters. The present work evaluated at lab-scale the potentialities of implementing a biotrickling filter (BTF) before the adsorption technology. Moreover, the use of ACs with different characteristics and price was evaluated considering their selectivity towards siloxane over volatile organic compounds (VOCs). The pre-treatment of biogas in a BTF capable of eliminating VOCs like limonene increased significantly the adsorbent performance, reaching 690 m(3) L-1 of biogas treated per bed volume by a phosphoric-activated carbon, a six-fold increase in the performance of currently used materials in adsorption treatment. In terms of cost, a steam-activated coal-based with a major mesoporosity contribution implied the lowest operating costs reaching 2.3 (sic) (1000 m(treated)(3))(-1). Coupling BTF with adsorption into this same AC resulted in lower annual costs than adsorption alone due to the frequent replacements required when biogas was not pre-polished. (C) 2020 Elsevier Ltd. All rights reserved.