Assessing macroscopic and microscopic performance of fungal-based biofilters for methane abatement

Abstract

Fungi have recently been shown to increase the performance of biofiltration in removing hydrophobic compounds like methane (CH4). The effectiveness of fungal-based biofiltration for treating low-concentrated (2% v/v) CH4 emissions was assessed in three biofilters (BFs) packed with expanded clay or compost and inoculated with fungal strains. The BFs were operated under different conditions of empty bed residence time (EBRT), pH of the mineral medium and irrigation. No CH4 removal was recorded in the BF inoculated with Candida subhashii and packed with expanded clay. Similarly, low CH4 abatement performances were observed for BF-1 and BF-2 inoculated with Fusarium solani and packed with expanded clay, with maximum removals of ∼36% when irrigated with MSM at a pH of 7 and operated at an EBRT of 42 min. Opposite, BF-3 packed with compost and inoculated with F. solani achieved average removals ranging from 80.3% (EC of 19 g m−3 h−1) at an EBRT of 34 min to 52.0% (EC of 22 g m−3 h−1) when decreasing the EBRT to 18 min. Amplicon metagenomics showed that CH4-degrading bacteria natural of compost were representative in BF-3. It also showed the importance of biostimulation in biofiltration for promoting methanotrophic growth. The fungal characterization revealed that a key factor on fungal BFs is the dominant fungi present. In this sense, Fusarium and clade LKM11 promoted methanotrophic growth. This knowledge can be applied to the operation of fungal BFs subjected to the treatment of CH4 via controlled bioaugmentation and biostimulation.