Black slag roman electric arc furnace (EAF) was used as an innovative inorganic co-packing material in organic biofilters for the biodegradation of CS2-polluted gases. The effect on biofilter performance of increasing the inlet concentration (IC) and reducing the empty bed residence time (EBRT) was evaluated in three Not-titers packed with different bed configurations. Macro-kinetic modelling pointed to a lower CS2 biodegradation activity related to the presence of the slag. Nevertheless, the presence of black slag improved long-term biofilter performance, and the maximum elimination capacity (43 g m(-3) 3 h(-1)) was recorded in the biofilter packed with a mixed support. Molecular profiling of the eubacterial populations demonstrated the ubiquitous presence of the potential CS2 degrading species Thiomonas intermedia. Co-packing with EAF slag also prompted the development of a more complex microbial community encompassing halophilic species involved in the metabolism of sulphur compounds (i.e. Thiohalophilus spp. and Paracoccus thiocyanatus). (C) 2015 Elsevier Ltd. All rights reserved.